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3.1.0-rc{0,1} doesn't start

Qemu-devel In review [email protected] 7 participants 22 messages Nov 18, 2018 – Dec 11, 2018

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[email protected]

author
#0 lore raw

hello

I'm building qemu from source and happily using it since a bit (2.3.0)

Since 3.1.0-rc0 (including latest 3.1.0-rc1) I'm no more able to start qemu, getting:

    ----8<----
    install:115> qemu
    qemu: error: failed to set MSR 0x10a to 0x0
    qemu: /home/balducci/tmp/install-us-d/qemu-3.1.0-rc1.d/qemu-3.1.0-rc0/target/i386/kvm.c:2185: kvm_put_msrs: Assertion `ret == cpu->kvm_msr_buf->nmsrs' failed.
    Aborted
    ---->8----

I have no idea about what the reason might be, apologies.

Actually, I have found a recent (2018-10-16) post which might be related to this (it mentions the same error message from qemu):
https://lkml.org/lkml/2018/10/16/440; but I'm not in the position to go through. AFAICS, the commit mentioned in the link is present in the 4.19.2 kernel I'm using, so...?

I can add that 3.0.0 works nicely (everything else unchanged, including running kernel 4.19.2)

OTOH, 3.1.0-rc0 dumps the same error message if I boot into 4.17.14 or 4.18.16 kernels.

I enclose my specs hoping that somebody can spot where the problem might be. I will be happy to send any other detail which might be useful.

I suspect that this might be some problem on my side, as I couldn't find any similar report (apart some old (qemu-2.8.50) threads, that didn't help)

thanks a lot in advance for any hint/help

ciao
gabriele

Here are my specs:

# --------------------------------

# command to run qemu is:
qemu -m 2G /opt/windog  \
    -accel kvm,thread=multi \
    -netdev user,id=net0,smb=/home/balducci \
    -device rtl8139,netdev=net0

# --------------------------------

# qemu build configuration:
--prefix=/opt/stow.d/versions/qemu-3.1.0-rc1/usr
--libdir=/opt/stow.d/versions/qemu-3.1.0-rc1/usr/lib64
--sysconfdir=/opt/stow.d/versions/qemu-3.1.0-rc1/etc
--localstatedir=/var/run
--docdir=/opt/stow.d/versions/qemu-3.1.0-rc1/usr/share/doc/qemu
--target-list=x86_64-softmmu
--audio-drv-list=alsa

# --------------------------------
install:154> uname -sr
Linux 4.19.2

# --------------------------------
install:155> cat /proc/cpuinfo
processor : 0
vendor_id : AuthenticAMD
cpu family : 21
model : 48
model name : AMD Athlon(tm) X4 860K Quad Core Processor
stepping : 1
microcode : 0x6003106
cpu MHz : 3473.492
cache size : 2048 KB
physical id : 0
siblings : 4
core id : 0
cpu cores : 2
apicid : 16
initial apicid : 0
fpu : yes
fpu_exception : yes
cpuid level : 13
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm constant_tsc rep_good nopl nonstop_tsc cpuid extd_apicid aperfmperf pni pclmulqdq monitor ssse3 fma cx16 sse4_1 sse4_2 popcnt aes xsave avx f16c lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs xop skinit wdt lwp fma4 tce nodeid_msr tbm topoext perfctr_core perfctr_nb bpext ptsc cpb hw_pstate ssbd vmmcall fsgsbase bmi1 xsaveopt arat npt lbrv svm_lock nrip_save tsc_scale vmcb_clean flushbyasid decodeassists pausefilter pfthreshold overflow_recov
bugs : fxsave_leak sysret_ss_attrs null_seg spectre_v1 spectre_v2 spec_store_bypass
bogomips : 7380.73
TLB size : 1536 4K pages
clflush size : 64
cache_alignment : 64
address sizes : 48 bits physical, 48 bits virtual
power management: ts ttp tm 100mhzsteps hwpstate cpb eff_freq_ro [13]

[...cpus 1 2 3 omitted...]

# --------------------------------
install:156> egrep KVM .config-4.19.2
CONFIG_HAVE_KVM=y
CONFIG_HAVE_KVM_IRQCHIP=y
CONFIG_HAVE_KVM_IRQFD=y
CONFIG_HAVE_KVM_IRQ_ROUTING=y
CONFIG_HAVE_KVM_EVENTFD=y
CONFIG_KVM_MMIO=y
CONFIG_KVM_ASYNC_PF=y
CONFIG_HAVE_KVM_MSI=y
CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT=y
CONFIG_KVM_VFIO=y
CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT=y
CONFIG_KVM_COMPAT=y
CONFIG_HAVE_KVM_IRQ_BYPASS=y
CONFIG_KVM=y
# CONFIG_KVM_INTEL is not set
CONFIG_KVM_AMD=y

[of course, I can send the whole kernel configuration file, if needed]

#1 lore raw

cc'ing in Paolo, Eduardo and Robert

Quoted 8 lines · * [email protected] ([email protected]) wrote:

hello

I'm building qemu from source and happily using it since a bit (2.3.0)

Since 3.1.0-rc0 (including latest 3.1.0-rc1) I'm no more able to start qemu, getting:

Quoted 8 lines
    ----8<----
    install:115> qemu
    qemu: error: failed to set MSR 0x10a to 0x0
    qemu: /home/balducci/tmp/install-us-d/qemu-3.1.0-rc1.d/qemu-3.1.0-rc0/target/i386/kvm.c:2185: kvm_put_msrs: Assertion `ret == cpu->kvm_msr_buf->nmsrs' failed.
    Aborted
    ---->8----

I have no idea about what the reason might be, apologies.

Thanks for the detailed error report.
MSR 0x10a is one of the new ones from the recent round of security things:

    #define MSR_IA32_ARCH_CAPABILITIES      0x10a

That only went in recently so is probably why you're seeing it in 3.1.

Quoted 5 lines

Actually, I have found a recent (2018-10-16) post which might be related to this (it mentions the same error message from qemu):
https://lkml.org/lkml/2018/10/16/440; but I'm not in the position to go through. AFAICS, the commit mentioned in the link is present in the 4.19.2 kernel I'm using, so...?

That's a different MSR number so is probably unrelated.

Quoted 6 lines

I can add that 3.0.0 works nicely (everything else unchanged, including running kernel 4.19.2)

OTOH, 3.1.0-rc0 dumps the same error message if I boot into 4.17.14 or 4.18.16 kernels.

Quoted 7 lines

I enclose my specs hoping that somebody can spot where the problem might be. I will be happy to send any other detail which might be useful.

I suspect that this might be some problem on my side, as I couldn't find any similar report (apart some old (qemu-2.8.50) threads, that didn't help)

Not necessarily; can you tell me:
a) At what point does it fail - immediately when booting the guest? Some time during the boot? Later?
b) What guest does it happen on?

Quoted 30 lines

thanks a lot in advance for any hint/help

ciao
gabriele

Here are my specs:

# --------------------------------

# command to run qemu is:
qemu -m 2G /opt/windog  \
    -accel kvm,thread=multi \
    -netdev user,id=net0,smb=/home/balducci \
    -device rtl8139,netdev=net0

# --------------------------------

# qemu build configuration:
--prefix=/opt/stow.d/versions/qemu-3.1.0-rc1/usr
--libdir=/opt/stow.d/versions/qemu-3.1.0-rc1/usr/lib64
--sysconfdir=/opt/stow.d/versions/qemu-3.1.0-rc1/etc
--localstatedir=/var/run
--docdir=/opt/stow.d/versions/qemu-3.1.0-rc1/usr/share/doc/qemu
--target-list=x86_64-softmmu
--audio-drv-list=alsa

# --------------------------------
install:154> uname -sr
Linux 4.19.2

Quoted 7 lines

# --------------------------------
install:155> cat /proc/cpuinfo
processor : 0
vendor_id : AuthenticAMD
cpu family : 21
model : 48
model name : AMD Athlon(tm) X4 860K Quad Core Processor

OK, older AMD cpu, so a little less tested perhaps, maybe why others haven't sene it.

Quoted 45 lines

stepping : 1
microcode : 0x6003106
cpu MHz : 3473.492
cache size : 2048 KB
physical id : 0
siblings : 4
core id : 0
cpu cores : 2
apicid : 16
initial apicid : 0
fpu : yes
fpu_exception : yes
cpuid level : 13
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm constant_tsc rep_good nopl nonstop_tsc cpuid extd_apicid aperfmperf pni pclmulqdq monitor ssse3 fma cx16 sse4_1 sse4_2 popcnt aes xsave avx f16c lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs xop skinit wdt lwp fma4 tce nodeid_msr tbm topoext perfctr_core perfctr_nb bpext ptsc cpb hw_pstate ssbd vmmcall fsgsbase bmi1 xsaveopt arat npt lbrv svm_lock nrip_save tsc_scale vmcb_clean flushbyasid decodeassists pausefilter pfthreshold overflow_recov
bugs : fxsave_leak sysret_ss_attrs null_seg spectre_v1 spectre_v2 spec_store_bypass
bogomips : 7380.73
TLB size : 1536 4K pages
clflush size : 64
cache_alignment : 64
address sizes : 48 bits physical, 48 bits virtual
power management: ts ttp tm 100mhzsteps hwpstate cpb eff_freq_ro [13]

[...cpus 1 2 3 omitted...]

# --------------------------------
install:156> egrep KVM .config-4.19.2
CONFIG_HAVE_KVM=y
CONFIG_HAVE_KVM_IRQCHIP=y
CONFIG_HAVE_KVM_IRQFD=y
CONFIG_HAVE_KVM_IRQ_ROUTING=y
CONFIG_HAVE_KVM_EVENTFD=y
CONFIG_KVM_MMIO=y
CONFIG_KVM_ASYNC_PF=y
CONFIG_HAVE_KVM_MSI=y
CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT=y
CONFIG_KVM_VFIO=y
CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT=y
CONFIG_KVM_COMPAT=y
CONFIG_HAVE_KVM_IRQ_BYPASS=y
CONFIG_KVM=y
# CONFIG_KVM_INTEL is not set
CONFIG_KVM_AMD=y

Quoted 1 line

[of course, I can send the whole kernel configuration file, if needed]

Dave

Quoted 1 line

--
Dr. David Alan Gilbert / [email protected] / Manchester, UK

author
#2 lore raw

hi

thanks for taking the time to reply

Quoted 8 lines · Dr. David Alan Gilbert
Quoted 3 lines

I suspect that this might be some problem on my side, as I couldn't find any similar report (apart some old (qemu-2.8.50) threads, that didn't help)

Not necessarily; can you tell me:
a) At what point does it fail - immediately when booting the guest? Some time during the boot? Later?
b) What guest does it happen on?

a) the error happens almost immediately; I mean: when I run qemu from an xterm, it doesn't even popup its window: it just dumps the error message to the terminal and stops
b) the guest is an old windows XP OS; but, as I say above, all goes as if qemu doesn't even load the OS image (at least this is my impression)

Meantime, I have tried to (quick&dirty) disable the error catching/asserting in i386/kvm.c:

install:41> diff ./qemu-3.1.0-rc1/target/i386/kvm.c.MSR_HACK ./qemu-3.1.0-rc1/target/i386/kvm.c 2205c2205
< if (ret < cpu->kvm_msr_buf->nmsrs) {
---

Quoted 1 line
    if (1==0) {

2211c2211
< assert(ret == cpu->kvm_msr_buf->nmsrs);
---

Quoted 1 line
    assert(1==1);

2524c2524
< if (ret < cpu->kvm_msr_buf->nmsrs) {
---

Quoted 1 line
    if (1==0) {

2530c2530
< assert(ret == cpu->kvm_msr_buf->nmsrs);
---

Quoted 1 line
    assert(1==1);

and that makes qemu start and work without apparent problems. Of course, that is a crude and risky (I guess) workaround...

thanks again

ciao
-gabriele

#3 lore raw
Quoted 14 lines · * [email protected] ([email protected]) wrote:

hi

thanks for taking the time to reply

Quoted 8 lines · Dr. David Alan Gilbert
Quoted 3 lines

I suspect that this might be some problem on my side, as I couldn't find any similar report (apart some old (qemu-2.8.50) threads, that didn't help)

Not necessarily; can you tell me:
a) At what point does it fail - immediately when booting the guest? Some time during the boot? Later?
b) What guest does it happen on?

Quoted 6 lines

a) the error happens almost immediately; I mean: when I run qemu from an xterm, it doesn't even popup its window: it just dumps the error message to the terminal and stops
b) the guest is an old windows XP OS; but, as I say above, all goes as if qemu doesn't even load the OS image (at least this is my impression)

Thanks.

Quoted 15 lines

Meantime, I have tried to (quick&dirty) disable the error catching/asserting in i386/kvm.c:

install:41> diff ./qemu-3.1.0-rc1/target/i386/kvm.c.MSR_HACK ./qemu-3.1.0-rc1/target/i386/kvm.c 2205c2205
< if (ret < cpu->kvm_msr_buf->nmsrs) {
---

Quoted 1 line
    if (1==0) {

2211c2211
< assert(ret == cpu->kvm_msr_buf->nmsrs);
---

Quoted 1 line
    assert(1==1);

2524c2524
< if (ret < cpu->kvm_msr_buf->nmsrs) {
---

Quoted 8 lines
Quoted 1 line
    if (1==0) {

2530c2530
< assert(ret == cpu->kvm_msr_buf->nmsrs);
---

Quoted 1 line
    assert(1==1);

and that makes qemu start and work without apparent problems. Of course, that is a crude and risky (I guess) workaround...

Yes, the gotcha is that the call writes a whole bunch of MSRs and when one fails all the ones after it don't get written either; so you get lots of weird problems due to whichever other MSRs are wrong.

Dave

Quoted 4 lines

thanks again

ciao
-gabriele

--
Dr. David Alan Gilbert / [email protected] / Manchester, UK

#4 lore raw
In reply to [email protected]
Quoted 14 lines · * [email protected] ([email protected]) wrote:

hi

thanks for taking the time to reply

Quoted 8 lines · Dr. David Alan Gilbert
Quoted 3 lines

I suspect that this might be some problem on my side, as I couldn't find any similar report (apart some old (qemu-2.8.50) threads, that didn't help)

Not necessarily; can you tell me:
a) At what point does it fail - immediately when booting the guest? Some time during the boot? Later?
b) What guest does it happen on?

Quoted 7 lines

a) the error happens almost immediately; I mean: when I run qemu from an xterm, it doesn't even popup its window: it just dumps the error message to the terminal and stops
b) the guest is an old windows XP OS; but, as I say above, all goes as if qemu doesn't even load the OS image (at least this is my impression)

A colleague has confirmed this on his FX-8320 on Fedora 29 with the virt-next repo; so it's nothing that's special about your machine; it's 3.1 that really doesn't like the old AMDs.

Dave

Quoted 21 lines

Meantime, I have tried to (quick&dirty) disable the error catching/asserting in i386/kvm.c:

install:41> diff ./qemu-3.1.0-rc1/target/i386/kvm.c.MSR_HACK ./qemu-3.1.0-rc1/target/i386/kvm.c 2205c2205
< if (ret < cpu->kvm_msr_buf->nmsrs) {
---

Quoted 1 line
    if (1==0) {

2211c2211
< assert(ret == cpu->kvm_msr_buf->nmsrs);
---

Quoted 1 line
    assert(1==1);

2524c2524
< if (ret < cpu->kvm_msr_buf->nmsrs) {
---

Quoted 1 line
    if (1==0) {

2530c2530
< assert(ret == cpu->kvm_msr_buf->nmsrs);
---

Quoted 1 line
    assert(1==1);
Quoted 7 lines

and that makes qemu start and work without apparent problems. Of course, that is a crude and risky (I guess) workaround...

thanks again

ciao
-gabriele

--
Dr. David Alan Gilbert / [email protected] / Manchester, UK

author
#5 lore raw
Quoted 3 lines

A colleague has confirmed this on his FX-8320 on Fedora 29 with the virt-next repo; so it's nothing that's special about your machine; it's 3.1 that really doesn't like the old AMDs.

ouch! does this mean that I must stop upgrading qemu or do you think that some development work will be directed towards this "back compatibility" issue?

(apologies for being totally unable to help with patches/code...I know zero about all the qemu business)

thanks a lot
ciao
-gabriele

#6 lore raw
Quoted 7 lines · * [email protected] ([email protected]) wrote:
Quoted 3 lines

A colleague has confirmed this on his FX-8320 on Fedora 29 with the virt-next repo; so it's nothing that's special about your machine; it's 3.1 that really doesn't like the old AMDs.

ouch! does this mean that I must stop upgrading qemu or do you think that some development work will be directed towards this "back compatibility" issue?

It'll probably be fixed; thanks to your report I've added it to the known issues part of the 3.1rc list.

Quoted 2 lines

(apologies for being totally unable to help with patches/code...I know zero about all the qemu business)

Those bits of the MSRs are pretty specialised as well; so I've asked a few people more familiar with them to jump in.

Dave

Quoted 3 lines

thanks a lot
ciao
-gabriele

--
Dr. David Alan Gilbert / [email protected] / Manchester, UK

#7 lore raw
In reply to Dr. David Alan Gilbert
Quoted 22 lines · Dr. David Alan Gilbert
Quoted 14 lines · * [email protected] ([email protected]) wrote:

hi

thanks for taking the time to reply

Quoted 8 lines · Dr. David Alan Gilbert
Quoted 3 lines

I suspect that this might be some problem on my side, as I couldn't find any similar report (apart some old (qemu-2.8.50) threads, that didn't help)

Not necessarily; can you tell me:
a) At what point does it fail - immediately when booting the guest? Some time during the boot? Later?
b) What guest does it happen on?

Quoted 7 lines

a) the error happens almost immediately; I mean: when I run qemu from an xterm, it doesn't even popup its window: it just dumps the error message to the terminal and stops
b) the guest is an old windows XP OS; but, as I say above, all goes as if qemu doesn't even load the OS image (at least this is my impression)

Quoted 4 lines

A colleague has confirmed this on his FX-8320 on Fedora 29 with the virt-next repo; so it's nothing that's special about your machine; it's 3.1 that really doesn't like the old AMDs.

Also we received a similar report in Fedora bugzilla:

https://bugzilla.redhat.com/show_bug.cgi?id=1651021

Thanks,
Cole

#8 lore raw
In reply to [email protected]
Quoted 8 lines · [email protected] writes:

hello

I'm building qemu from source and happily using it since a bit (2.3.0)

Since 3.1.0-rc0 (including latest 3.1.0-rc1) I'm no more able to start qemu, getting:

Quoted 7 lines
    ----8<----
    install:115> qemu
    qemu: error: failed to set MSR 0x10a to 0x0
    qemu: /home/balducci/tmp/install-us-d/qemu-3.1.0-rc1.d/qemu-3.1.0-rc0/target/i386/kvm.c:2185: kvm_put_msrs: Assertion `ret == cpu->kvm_msr_buf->nmsrs' failed.
    Aborted
    ---->8----

I believe the check on whether MSR_IA32_ARCH_CAPABILITIES is present is incomplete because it can return 0 for data. Can you try this:

target/i386/kvm.c +2 -7
index f524e7d929..4878ffb90b 100644
@@ -2002,14 +2002,9 @@ static int kvm_put_msrs(X86CPU *cpu, int level)
 #endif
 
     /* If host supports feature MSR, write down. */
-    if (kvm_feature_msrs) {
-        int i;
-        for (i = 0; i < kvm_feature_msrs->nmsrs; i++)
-            if (kvm_feature_msrs->indices[i] == MSR_IA32_ARCH_CAPABILITIES) {
-                kvm_msr_entry_add(cpu, MSR_IA32_ARCH_CAPABILITIES,
+    if (kvm_arch_get_supported_msr_feature(kvm_state, MSR_IA32_ARCH_CAPABILITIES)) {
+        kvm_msr_entry_add(cpu, MSR_IA32_ARCH_CAPABILITIES,
                               env->features[FEAT_ARCH_CAPABILITIES]);
-                break;
-            }
     }
 
     /*
Quoted 106 lines

I have no idea about what the reason might be, apologies.

Actually, I have found a recent (2018-10-16) post which might be related to this (it mentions the same error message from qemu):
https://lkml.org/lkml/2018/10/16/440; but I'm not in the position to go through. AFAICS, the commit mentioned in the link is present in the 4.19.2 kernel I'm using, so...?

I can add that 3.0.0 works nicely (everything else unchanged, including running kernel 4.19.2)

OTOH, 3.1.0-rc0 dumps the same error message if I boot into 4.17.14 or 4.18.16 kernels.

I enclose my specs hoping that somebody can spot where the problem might be. I will be happy to send any other detail which might be useful.

I suspect that this might be some problem on my side, as I couldn't find any similar report (apart some old (qemu-2.8.50) threads, that didn't help)

thanks a lot in advance for any hint/help

ciao
gabriele

Here are my specs:

# --------------------------------

# command to run qemu is:
qemu -m 2G /opt/windog  \
    -accel kvm,thread=multi \
    -netdev user,id=net0,smb=/home/balducci \
    -device rtl8139,netdev=net0

# --------------------------------

# qemu build configuration:
--prefix=/opt/stow.d/versions/qemu-3.1.0-rc1/usr
--libdir=/opt/stow.d/versions/qemu-3.1.0-rc1/usr/lib64
--sysconfdir=/opt/stow.d/versions/qemu-3.1.0-rc1/etc
--localstatedir=/var/run
--docdir=/opt/stow.d/versions/qemu-3.1.0-rc1/usr/share/doc/qemu
--target-list=x86_64-softmmu
--audio-drv-list=alsa

# --------------------------------
install:154> uname -sr
Linux 4.19.2

# --------------------------------
install:155> cat /proc/cpuinfo
processor : 0
vendor_id : AuthenticAMD
cpu family : 21
model : 48
model name : AMD Athlon(tm) X4 860K Quad Core Processor
stepping : 1
microcode : 0x6003106
cpu MHz : 3473.492
cache size : 2048 KB
physical id : 0
siblings : 4
core id : 0
cpu cores : 2
apicid : 16
initial apicid : 0
fpu : yes
fpu_exception : yes
cpuid level : 13
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm constant_tsc rep_good nopl nonstop_tsc cpuid extd_apicid aperfmperf pni pclmulqdq monitor ssse3 fma cx16 sse4_1 sse4_2 popcnt aes xsave avx f16c lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs xop skinit wdt lwp fma4 tce nodeid_msr tbm topoext perfctr_core perfctr_nb bpext ptsc cpb hw_pstate ssbd vmmcall fsgsbase bmi1 xsaveopt arat npt lbrv svm_lock nrip_save tsc_scale vmcb_clean flushbyasid decodeassists pausefilter pfthreshold overflow_recov
bugs : fxsave_leak sysret_ss_attrs null_seg spectre_v1 spectre_v2 spec_store_bypass
bogomips : 7380.73
TLB size : 1536 4K pages
clflush size : 64
cache_alignment : 64
address sizes : 48 bits physical, 48 bits virtual
power management: ts ttp tm 100mhzsteps hwpstate cpb eff_freq_ro [13]

[...cpus 1 2 3 omitted...]

# --------------------------------
install:156> egrep KVM .config-4.19.2
CONFIG_HAVE_KVM=y
CONFIG_HAVE_KVM_IRQCHIP=y
CONFIG_HAVE_KVM_IRQFD=y
CONFIG_HAVE_KVM_IRQ_ROUTING=y
CONFIG_HAVE_KVM_EVENTFD=y
CONFIG_KVM_MMIO=y
CONFIG_KVM_ASYNC_PF=y
CONFIG_HAVE_KVM_MSI=y
CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT=y
CONFIG_KVM_VFIO=y
CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT=y
CONFIG_KVM_COMPAT=y
CONFIG_HAVE_KVM_IRQ_BYPASS=y
CONFIG_KVM=y
# CONFIG_KVM_INTEL is not set
CONFIG_KVM_AMD=y

[of course, I can send the whole kernel configuration file, if needed]

#9 lore raw
Quoted 26 lines · Bandan Das
Quoted 8 lines · [email protected] writes:

hello

I'm building qemu from source and happily using it since a bit (2.3.0)

Since 3.1.0-rc0 (including latest 3.1.0-rc1) I'm no more able to start qemu, getting:

Quoted 7 lines
    ----8<----
    install:115> qemu
    qemu: error: failed to set MSR 0x10a to 0x0
    qemu: /home/balducci/tmp/install-us-d/qemu-3.1.0-rc1.d/qemu-3.1.0-rc0/target/i386/kvm.c:2185: kvm_put_msrs: Assertion `ret == cpu->kvm_msr_buf->nmsrs' failed.
    Aborted
    ---->8----

I believe the check on whether MSR_IA32_ARCH_CAPABILITIES is present is incomplete because it can return 0 for data. Can you try this:

target/i386/kvm.c +0 -0
index f524e7d929..4878ffb90b 100644
@@ -2002,14 +2002,9 @@ static int kvm_put_msrs(X86CPU *cpu, int level)
 #endif

target/i386/kvm.c static int kvm_put_msrs(X86CPU *cpu, int level) · line 2007

Quoted 10 lines
target/i386/kvm.c +2 -5
 
     /* If host supports feature MSR, write down. */
-    if (kvm_feature_msrs) {
-        int i;
-        for (i = 0; i < kvm_feature_msrs->nmsrs; i++)
-            if (kvm_feature_msrs->indices[i] == MSR_IA32_ARCH_CAPABILITIES) {
-                kvm_msr_entry_add(cpu, MSR_IA32_ARCH_CAPABILITIES,
+    if (kvm_arch_get_supported_msr_feature(kvm_state, MSR_IA32_ARCH_CAPABILITIES)) {
+        kvm_msr_entry_add(cpu, MSR_IA32_ARCH_CAPABILITIES,
                               env->features[FEAT_ARCH_CAPABILITIES]);

kvm_arch_get_supported_msr_feature() will return the value of the MSR on the host side (kvm/x86.c:kvm_get_msr_feature()). Having it return non-zero doesn't mean KVM's svm_set_msr(MSR_IA32_ARCH_CAPABILITIES) will work.

If the MSR doesn't work on KVM_SET_MSRS, it is not supposed to appear on KVM_GET_MSR_INDEX_LIST (even if it appears on KVM_GET_MSR_FEATURE_INDEX_LIST). QEMU must check KVM_GET_MSR_INDEX_LIST too before including the MSR on the KVM_SET_MSRS call.

Quoted 113 lines
target/i386/kvm.c +0 -2
-                break;
-            }
     }
 
     /*
Quoted 108 lines

I have no idea about what the reason might be, apologies.

Actually, I have found a recent (2018-10-16) post which might be related to this (it mentions the same error message from qemu):
https://lkml.org/lkml/2018/10/16/440; but I'm not in the position to go through. AFAICS, the commit mentioned in the link is present in the 4.19.2 kernel I'm using, so...?

I can add that 3.0.0 works nicely (everything else unchanged, including running kernel 4.19.2)

OTOH, 3.1.0-rc0 dumps the same error message if I boot into 4.17.14 or 4.18.16 kernels.

I enclose my specs hoping that somebody can spot where the problem might be. I will be happy to send any other detail which might be useful.

I suspect that this might be some problem on my side, as I couldn't find any similar report (apart some old (qemu-2.8.50) threads, that didn't help)

thanks a lot in advance for any hint/help

ciao
gabriele

Here are my specs:

# --------------------------------

# command to run qemu is:
qemu -m 2G /opt/windog  \
    -accel kvm,thread=multi \
    -netdev user,id=net0,smb=/home/balducci \
    -device rtl8139,netdev=net0

# --------------------------------

# qemu build configuration:
--prefix=/opt/stow.d/versions/qemu-3.1.0-rc1/usr
--libdir=/opt/stow.d/versions/qemu-3.1.0-rc1/usr/lib64
--sysconfdir=/opt/stow.d/versions/qemu-3.1.0-rc1/etc
--localstatedir=/var/run
--docdir=/opt/stow.d/versions/qemu-3.1.0-rc1/usr/share/doc/qemu
--target-list=x86_64-softmmu
--audio-drv-list=alsa

# --------------------------------
install:154> uname -sr
Linux 4.19.2

# --------------------------------
install:155> cat /proc/cpuinfo
processor : 0
vendor_id : AuthenticAMD
cpu family : 21
model : 48
model name : AMD Athlon(tm) X4 860K Quad Core Processor
stepping : 1
microcode : 0x6003106
cpu MHz : 3473.492
cache size : 2048 KB
physical id : 0
siblings : 4
core id : 0
cpu cores : 2
apicid : 16
initial apicid : 0
fpu : yes
fpu_exception : yes
cpuid level : 13
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm constant_tsc rep_good nopl nonstop_tsc cpuid extd_apicid aperfmperf pni pclmulqdq monitor ssse3 fma cx16 sse4_1 sse4_2 popcnt aes xsave avx f16c lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs xop skinit wdt lwp fma4 tce nodeid_msr tbm topoext perfctr_core perfctr_nb bpext ptsc cpb hw_pstate ssbd vmmcall fsgsbase bmi1 xsaveopt arat npt lbrv svm_lock nrip_save tsc_scale vmcb_clean flushbyasid decodeassists pausefilter pfthreshold overflow_recov
bugs : fxsave_leak sysret_ss_attrs null_seg spectre_v1 spectre_v2 spec_store_bypass
bogomips : 7380.73
TLB size : 1536 4K pages
clflush size : 64
cache_alignment : 64
address sizes : 48 bits physical, 48 bits virtual
power management: ts ttp tm 100mhzsteps hwpstate cpb eff_freq_ro [13]

[...cpus 1 2 3 omitted...]

# --------------------------------
install:156> egrep KVM .config-4.19.2
CONFIG_HAVE_KVM=y
CONFIG_HAVE_KVM_IRQCHIP=y
CONFIG_HAVE_KVM_IRQFD=y
CONFIG_HAVE_KVM_IRQ_ROUTING=y
CONFIG_HAVE_KVM_EVENTFD=y
CONFIG_KVM_MMIO=y
CONFIG_KVM_ASYNC_PF=y
CONFIG_HAVE_KVM_MSI=y
CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT=y
CONFIG_KVM_VFIO=y
CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT=y
CONFIG_KVM_COMPAT=y
CONFIG_HAVE_KVM_IRQ_BYPASS=y
CONFIG_KVM=y
# CONFIG_KVM_INTEL is not set
CONFIG_KVM_AMD=y

[of course, I can send the whole kernel configuration file, if needed]

Signature · 1 line
Eduardo
#10 lore raw
Quoted 43 lines · Eduardo Habkost
Quoted 26 lines · Bandan Das
Quoted 8 lines · [email protected] writes:

hello

I'm building qemu from source and happily using it since a bit (2.3.0)

Since 3.1.0-rc0 (including latest 3.1.0-rc1) I'm no more able to start qemu, getting:

Quoted 7 lines
    ----8<----
    install:115> qemu
    qemu: error: failed to set MSR 0x10a to 0x0
    qemu: /home/balducci/tmp/install-us-d/qemu-3.1.0-rc1.d/qemu-3.1.0-rc0/target/i386/kvm.c:2185: kvm_put_msrs: Assertion `ret == cpu->kvm_msr_buf->nmsrs' failed.
    Aborted
    ---->8----

I believe the check on whether MSR_IA32_ARCH_CAPABILITIES is present is incomplete because it can return 0 for data. Can you try this:

target/i386/kvm.c +0 -0
index f524e7d929..4878ffb90b 100644
@@ -2002,14 +2002,9 @@ static int kvm_put_msrs(X86CPU *cpu, int level)
 #endif

target/i386/kvm.c static int kvm_put_msrs(X86CPU *cpu, int level) · line 2007

Quoted 10 lines
target/i386/kvm.c +2 -5
 
     /* If host supports feature MSR, write down. */
-    if (kvm_feature_msrs) {
-        int i;
-        for (i = 0; i < kvm_feature_msrs->nmsrs; i++)
-            if (kvm_feature_msrs->indices[i] == MSR_IA32_ARCH_CAPABILITIES) {
-                kvm_msr_entry_add(cpu, MSR_IA32_ARCH_CAPABILITIES,
+    if (kvm_arch_get_supported_msr_feature(kvm_state, MSR_IA32_ARCH_CAPABILITIES)) {
+        kvm_msr_entry_add(cpu, MSR_IA32_ARCH_CAPABILITIES,
                               env->features[FEAT_ARCH_CAPABILITIES]);

kvm_arch_get_supported_msr_feature() will return the value of the MSR on the host side (kvm/x86.c:kvm_get_msr_feature()). Having it return non-zero doesn't mean KVM's svm_set_msr(MSR_IA32_ARCH_CAPABILITIES) will work.

Quoted 5 lines

If the MSR doesn't work on KVM_SET_MSRS, it is not supposed to appear on KVM_GET_MSR_INDEX_LIST (even if it appears on KVM_GET_MSR_FEATURE_INDEX_LIST). QEMU must check KVM_GET_MSR_INDEX_LIST too before including the MSR on the KVM_SET_MSRS call.

Yes, this is a KVM bug. For 3.1, making it "writable if nonzero" is a valid workaround, because AMD processors always return 0. It's not the prettiest thing, but it works.

Paolo

#11 lore raw
Quoted 50 lines · Paolo Bonzini
Quoted 43 lines · Eduardo Habkost
Quoted 26 lines · Bandan Das
Quoted 8 lines · [email protected] writes:

hello

I'm building qemu from source and happily using it since a bit (2.3.0)

Since 3.1.0-rc0 (including latest 3.1.0-rc1) I'm no more able to start qemu, getting:

Quoted 7 lines
    ----8<----
    install:115> qemu
    qemu: error: failed to set MSR 0x10a to 0x0
    qemu: /home/balducci/tmp/install-us-d/qemu-3.1.0-rc1.d/qemu-3.1.0-rc0/target/i386/kvm.c:2185: kvm_put_msrs: Assertion `ret == cpu->kvm_msr_buf->nmsrs' failed.
    Aborted
    ---->8----

I believe the check on whether MSR_IA32_ARCH_CAPABILITIES is present is incomplete because it can return 0 for data. Can you try this:

target/i386/kvm.c +0 -0
index f524e7d929..4878ffb90b 100644
@@ -2002,14 +2002,9 @@ static int kvm_put_msrs(X86CPU *cpu, int level)
 #endif

target/i386/kvm.c static int kvm_put_msrs(X86CPU *cpu, int level) · line 2007

Quoted 10 lines
target/i386/kvm.c +2 -5
 
     /* If host supports feature MSR, write down. */
-    if (kvm_feature_msrs) {
-        int i;
-        for (i = 0; i < kvm_feature_msrs->nmsrs; i++)
-            if (kvm_feature_msrs->indices[i] == MSR_IA32_ARCH_CAPABILITIES) {
-                kvm_msr_entry_add(cpu, MSR_IA32_ARCH_CAPABILITIES,
+    if (kvm_arch_get_supported_msr_feature(kvm_state, MSR_IA32_ARCH_CAPABILITIES)) {
+        kvm_msr_entry_add(cpu, MSR_IA32_ARCH_CAPABILITIES,
                               env->features[FEAT_ARCH_CAPABILITIES]);

kvm_arch_get_supported_msr_feature() will return the value of the MSR on the host side (kvm/x86.c:kvm_get_msr_feature()). Having it return non-zero doesn't mean KVM's svm_set_msr(MSR_IA32_ARCH_CAPABILITIES) will work.

Quoted 5 lines

If the MSR doesn't work on KVM_SET_MSRS, it is not supposed to appear on KVM_GET_MSR_INDEX_LIST (even if it appears on KVM_GET_MSR_FEATURE_INDEX_LIST). QEMU must check KVM_GET_MSR_INDEX_LIST too before including the MSR on the KVM_SET_MSRS call.

Quoted 3 lines

Yes, this is a KVM bug. For 3.1, making it "writable if nonzero" is a valid workaround, because AMD processors always return 0. It's not the prettiest thing, but it works.

So it looks like we have 2 bugs? Is KVM incorrectly returning the MSR on KVM_GET_MSR_INDEX_LIST?

I thought the bug was only in QEMU, which is supposed to be checking KVM_GET_MSR_INDEX_LIST before setting the MSR (it is only checking KVM_GET_MSR_FEATURE_INDEX_LIST).

Signature · 1 line
Eduardo
#12 lore raw
Quoted 55 lines · Eduardo Habkost
Quoted 50 lines · Paolo Bonzini
Quoted 43 lines · Eduardo Habkost
Quoted 26 lines · Bandan Das
Quoted 8 lines · [email protected] writes:

hello

I'm building qemu from source and happily using it since a bit (2.3.0)

Since 3.1.0-rc0 (including latest 3.1.0-rc1) I'm no more able to start qemu, getting:

Quoted 7 lines
    ----8<----
    install:115> qemu
    qemu: error: failed to set MSR 0x10a to 0x0
    qemu: /home/balducci/tmp/install-us-d/qemu-3.1.0-rc1.d/qemu-3.1.0-rc0/target/i386/kvm.c:2185: kvm_put_msrs: Assertion `ret == cpu->kvm_msr_buf->nmsrs' failed.
    Aborted
    ---->8----

I believe the check on whether MSR_IA32_ARCH_CAPABILITIES is present is incomplete because it can return 0 for data. Can you try this:

target/i386/kvm.c +0 -0
index f524e7d929..4878ffb90b 100644
@@ -2002,14 +2002,9 @@ static int kvm_put_msrs(X86CPU *cpu, int level)
 #endif

target/i386/kvm.c static int kvm_put_msrs(X86CPU *cpu, int level) · line 2007

Quoted 10 lines
target/i386/kvm.c +2 -5
 
     /* If host supports feature MSR, write down. */
-    if (kvm_feature_msrs) {
-        int i;
-        for (i = 0; i < kvm_feature_msrs->nmsrs; i++)
-            if (kvm_feature_msrs->indices[i] == MSR_IA32_ARCH_CAPABILITIES) {
-                kvm_msr_entry_add(cpu, MSR_IA32_ARCH_CAPABILITIES,
+    if (kvm_arch_get_supported_msr_feature(kvm_state, MSR_IA32_ARCH_CAPABILITIES)) {
+        kvm_msr_entry_add(cpu, MSR_IA32_ARCH_CAPABILITIES,
                               env->features[FEAT_ARCH_CAPABILITIES]);

kvm_arch_get_supported_msr_feature() will return the value of the MSR on the host side (kvm/x86.c:kvm_get_msr_feature()). Having it return non-zero doesn't mean KVM's svm_set_msr(MSR_IA32_ARCH_CAPABILITIES) will work.

Quoted 5 lines

If the MSR doesn't work on KVM_SET_MSRS, it is not supposed to appear on KVM_GET_MSR_INDEX_LIST (even if it appears on KVM_GET_MSR_FEATURE_INDEX_LIST). QEMU must check KVM_GET_MSR_INDEX_LIST too before including the MSR on the KVM_SET_MSRS call.

Quoted 3 lines

Yes, this is a KVM bug. For 3.1, making it "writable if nonzero" is a valid workaround, because AMD processors always return 0. It's not the prettiest thing, but it works.

Quoted 6 lines

So it looks like we have 2 bugs? Is KVM incorrectly returning the MSR on KVM_GET_MSR_INDEX_LIST?

I thought the bug was only in QEMU, which is supposed to be checking KVM_GET_MSR_INDEX_LIST before setting the MSR (it is only checking KVM_GET_MSR_FEATURE_INDEX_LIST).

Oh, wait. I didn't understand that. Then yeah, fixing QEMU is enough.
KVM is not reporting the MSR in the list on AMD, but it should (and it
should implement the MSR, of course!).

Paolo

#13 lore raw

Paolo Bonzini <[email protected]> writes:
...

Quoted 35 lines
Quoted 35 lines
Quoted 28 lines
Quoted 22 lines
Quoted 6 lines
target/i386/kvm.c +0 -0
index f524e7d929..4878ffb90b 100644
@@ -2002,14 +2002,9 @@ static int kvm_put_msrs(X86CPU *cpu, int level)
 #endif

target/i386/kvm.c static int kvm_put_msrs(X86CPU *cpu, int level) · line 2007

Quoted 10 lines
target/i386/kvm.c +2 -5
 
     /* If host supports feature MSR, write down. */
-    if (kvm_feature_msrs) {
-        int i;
-        for (i = 0; i < kvm_feature_msrs->nmsrs; i++)
-            if (kvm_feature_msrs->indices[i] == MSR_IA32_ARCH_CAPABILITIES) {
-                kvm_msr_entry_add(cpu, MSR_IA32_ARCH_CAPABILITIES,
+    if (kvm_arch_get_supported_msr_feature(kvm_state, MSR_IA32_ARCH_CAPABILITIES)) {
+        kvm_msr_entry_add(cpu, MSR_IA32_ARCH_CAPABILITIES,
                               env->features[FEAT_ARCH_CAPABILITIES]);

kvm_arch_get_supported_msr_feature() will return the value of the MSR on the host side (kvm/x86.c:kvm_get_msr_feature()). Having it return non-zero doesn't mean KVM's svm_set_msr(MSR_IA32_ARCH_CAPABILITIES) will work.

Quoted 5 lines

If the MSR doesn't work on KVM_SET_MSRS, it is not supposed to appear on KVM_GET_MSR_INDEX_LIST (even if it appears on KVM_GET_MSR_FEATURE_INDEX_LIST). QEMU must check KVM_GET_MSR_INDEX_LIST too before including the MSR on the KVM_SET_MSRS call.

Quoted 3 lines

Yes, this is a KVM bug. For 3.1, making it "writable if nonzero" is a valid workaround, because AMD processors always return 0. It's not the prettiest thing, but it works.

So it looks like we have 2 bugs? Is KVM incorrectly returning the MSR on KVM_GET_MSR_INDEX_LIST?

Quoted 8 lines
Quoted 3 lines

I thought the bug was only in QEMU, which is supposed to be checking KVM_GET_MSR_INDEX_LIST before setting the MSR (it is only checking KVM_GET_MSR_FEATURE_INDEX_LIST).

Oh, wait. I didn't understand that. Then yeah, fixing QEMU is enough.
KVM is not reporting the MSR in the list on AMD, but it should (and it
should implement the MSR, of course!).

Until AMD implements somethinig, on the KVM side, shouldn't we let kvm_x86_ops->get_msr_feature(msr)) handle MSR_IA32_ARCH_CAPABILITIES ?

Quoted 1 line

Paolo

#14 lore raw
Quoted 7 lines · Bandan Das
Quoted 4 lines

Oh, wait. I didn't understand that. Then yeah, fixing QEMU is enough.
KVM is not reporting the MSR in the list on AMD, but it should (and it
should implement the MSR, of course!).

Until AMD implements somethinig, on the KVM side, shouldn't we let kvm_x86_ops->get_msr_feature(msr)) handle MSR_IA32_ARCH_CAPABILITIES ?

Either is okay. But the MSR is not really vendor dependent, and can be added even to older models. So it may make sense to move it to generic code.

Paolo

author
#15 lore raw
In reply to Bandan Das

hello

Quoted 24 lines

incomplete because it can return 0 for data. Can you try this:

target/i386/kvm.c +2 -7
index f524e7d929..4878ffb90b 100644
@@ -2002,14 +2002,9 @@ static int kvm_put_msrs(X86CPU *cpu, int level)
 #endif
 
     /* If host supports feature MSR, write down. */
-    if (kvm_feature_msrs) {
-        int i;
-        for (i = 0; i < kvm_feature_msrs->nmsrs; i++)
-            if (kvm_feature_msrs->indices[i] == MSR_IA32_ARCH_CAPABILITIES) 
 {
-                kvm_msr_entry_add(cpu, MSR_IA32_ARCH_CAPABILITIES,
+    if (kvm_arch_get_supported_msr_feature(kvm_state, MSR_IA32_ARCH_CAPABILI
 TIES)) {
+        kvm_msr_entry_add(cpu, MSR_IA32_ARCH_CAPABILITIES,
                               env->features[FEAT_ARCH_CAPABILITIES]);
-                break;
-            }
     }
Quoted 1 line
     /*

I'm getting the same error message at start time (patch applied to official qemu-3.1.0-rc1 tarball):

----8<----
qemu: error: failed to set MSR 0x10a to 0x0
qemu: /home/balducci/tmp/install-us-d/qemu-3.1.0-rc1.d/qemu-3.1.0-rc1/target/i386/kvm.c:2206: kvm_put_msrs: Assertion `ret == cpu->kvm_msr_buf->nmsrs' failed. Aborted
---->8----

thanks a lot
ciao
-gabriele

#16 lore raw
Quoted 26 lines · [email protected] writes:

hello

Quoted 24 lines

incomplete because it can return 0 for data. Can you try this:

target/i386/kvm.c +2 -7
index f524e7d929..4878ffb90b 100644
@@ -2002,14 +2002,9 @@ static int kvm_put_msrs(X86CPU *cpu, int level)
 #endif
 
     /* If host supports feature MSR, write down. */
-    if (kvm_feature_msrs) {
-        int i;
-        for (i = 0; i < kvm_feature_msrs->nmsrs; i++)
-            if (kvm_feature_msrs->indices[i] == MSR_IA32_ARCH_CAPABILITIES) 
 {
-                kvm_msr_entry_add(cpu, MSR_IA32_ARCH_CAPABILITIES,
+    if (kvm_arch_get_supported_msr_feature(kvm_state, MSR_IA32_ARCH_CAPABILI
 TIES)) {
+        kvm_msr_entry_add(cpu, MSR_IA32_ARCH_CAPABILITIES,
                               env->features[FEAT_ARCH_CAPABILITIES]);
-                break;
-            }
     }
Quoted 2 lines
Quoted 1 line
     /*

Sorry Gabriele, Eduardo and Paolo pointed out that the patch was incomplete. I am not sure however how you are getting non zero data with the rdmsr on an AMD. Can you please try this instead ?

target/i386/kvm.c +6 -6
index f524e7d929..cfec559aa3 100644
@@ -95,6 +95,7 @@ static bool has_msr_xss;
 static bool has_msr_spec_ctrl;
 static bool has_msr_virt_ssbd;
 static bool has_msr_smi_count;
+static bool has_msr_arch_capabs;
 
 static uint32_t has_architectural_pmu_version;
 static uint32_t num_architectural_pmu_gp_counters;

@@ -1481,6 +1482,9 @@ static int kvm_get_supported_msrs(KVMState *s)
                 case MSR_VIRT_SSBD:
                     has_msr_virt_ssbd = true;
                     break;
+                case MSR_IA32_ARCH_CAPABILITIES:
+                    has_msr_arch_capabs = true;
+                    break;
                 }
             }
         }

@@ -2002,14 +2006,10 @@ static int kvm_put_msrs(X86CPU *cpu, int level)
 #endif
 
     /* If host supports feature MSR, write down. */
-    if (kvm_feature_msrs) {
-        int i;
-        for (i = 0; i < kvm_feature_msrs->nmsrs; i++)
-            if (kvm_feature_msrs->indices[i] == MSR_IA32_ARCH_CAPABILITIES) {
+    if (kvm_arch_get_supported_msr_feature(kvm_state, MSR_IA32_ARCH_CAPABILITIES)
+        && has_msr_arch_capabs) {
                 kvm_msr_entry_add(cpu, MSR_IA32_ARCH_CAPABILITIES,
                               env->features[FEAT_ARCH_CAPABILITIES]);
-                break;
-            }
     }
 
     /*
author
#17 lore raw
Quoted 45 lines

Sorry Gabriele, Eduardo and Paolo pointed out that the patch was incomplete. I am not sure however how you are getting non zero data with the rdmsr on an AMD.
Can you please try this instead ?

target/i386/kvm.c +6 -6
index f524e7d929..cfec559aa3 100644
@@ -95,6 +95,7 @@ static bool has_msr_xss;
 static bool has_msr_spec_ctrl;
 static bool has_msr_virt_ssbd;
 static bool has_msr_smi_count;
+static bool has_msr_arch_capabs;
 
 static uint32_t has_architectural_pmu_version;
 static uint32_t num_architectural_pmu_gp_counters;

@@ -1481,6 +1482,9 @@ static int kvm_get_supported_msrs(KVMState *s)
                 case MSR_VIRT_SSBD:
                     has_msr_virt_ssbd = true;
                     break;
+                case MSR_IA32_ARCH_CAPABILITIES:
+                    has_msr_arch_capabs = true;
+                    break;
                 }
             }
         }

@@ -2002,14 +2006,10 @@ static int kvm_put_msrs(X86CPU *cpu, int level)
 #endif
 
     /* If host supports feature MSR, write down. */
-    if (kvm_feature_msrs) {
-        int i;
-        for (i = 0; i < kvm_feature_msrs->nmsrs; i++)
-            if (kvm_feature_msrs->indices[i] == MSR_IA32_ARCH_CAPABILITIES) 
 {
+    if (kvm_arch_get_supported_msr_feature(kvm_state, MSR_IA32_ARCH_CAPABILI
 TIES)
+        && has_msr_arch_capabs) {
                 kvm_msr_entry_add(cpu, MSR_IA32_ARCH_CAPABILITIES,
                               env->features[FEAT_ARCH_CAPABILITIES]);
-                break;
-            }
     }
Quoted 1 line
     /*

this one works: qemu starts without any complaint and behaves as usual (AFAICS)

thank you very much for working on this

ciao
gabriele

#18 lore raw
In reply to Bandan Das
Quoted 57 lines · Bandan Das
Quoted 26 lines · [email protected] writes:

hello

Quoted 24 lines

incomplete because it can return 0 for data. Can you try this:

target/i386/kvm.c +2 -7
index f524e7d929..4878ffb90b 100644
@@ -2002,14 +2002,9 @@ static int kvm_put_msrs(X86CPU *cpu, int level)
 #endif
 
     /* If host supports feature MSR, write down. */
-    if (kvm_feature_msrs) {
-        int i;
-        for (i = 0; i < kvm_feature_msrs->nmsrs; i++)
-            if (kvm_feature_msrs->indices[i] == MSR_IA32_ARCH_CAPABILITIES) 
 {
-                kvm_msr_entry_add(cpu, MSR_IA32_ARCH_CAPABILITIES,
+    if (kvm_arch_get_supported_msr_feature(kvm_state, MSR_IA32_ARCH_CAPABILI
 TIES)) {
+        kvm_msr_entry_add(cpu, MSR_IA32_ARCH_CAPABILITIES,
                               env->features[FEAT_ARCH_CAPABILITIES]);
-                break;
-            }
     }
Quoted 2 lines
Quoted 1 line
     /*

Sorry Gabriele, Eduardo and Paolo pointed out that the patch was incomplete. I am not sure however how you are getting non zero data with the rdmsr on an AMD. Can you please try this instead ?

target/i386/kvm.c +4 -0
index f524e7d929..cfec559aa3 100644
@@ -95,6 +95,7 @@ static bool has_msr_xss;
 static bool has_msr_spec_ctrl;
 static bool has_msr_virt_ssbd;
 static bool has_msr_smi_count;
+static bool has_msr_arch_capabs;
 
 static uint32_t has_architectural_pmu_version;
 static uint32_t num_architectural_pmu_gp_counters;

@@ -1481,6 +1482,9 @@ static int kvm_get_supported_msrs(KVMState *s)
                 case MSR_VIRT_SSBD:
                     has_msr_virt_ssbd = true;
                     break;
+                case MSR_IA32_ARCH_CAPABILITIES:
+                    has_msr_arch_capabs = true;
+                    break;
                 }
             }
         }

target/i386/kvm.c static int kvm_put_msrs(X86CPU *cpu, int level) · line 2010

Quoted 9 lines
target/i386/kvm.c +2 -4
@@ -2002,14 +2006,10 @@ static int kvm_put_msrs(X86CPU *cpu, int level)
 #endif
 
     /* If host supports feature MSR, write down. */
-    if (kvm_feature_msrs) {
-        int i;
-        for (i = 0; i < kvm_feature_msrs->nmsrs; i++)
-            if (kvm_feature_msrs->indices[i] == MSR_IA32_ARCH_CAPABILITIES) {
+    if (kvm_arch_get_supported_msr_feature(kvm_state, MSR_IA32_ARCH_CAPABILITIES)
+        && has_msr_arch_capabs) {

Unless we have a KVM bug too, has_msr_arch_capabs should be enough.

If has_msr_arch_capabs is not enough, we'll need to add a comment explaining why, or we risk reintroducing the same bug later.

Quoted 9 lines
target/i386/kvm.c +0 -2
                 kvm_msr_entry_add(cpu, MSR_IA32_ARCH_CAPABILITIES,
                               env->features[FEAT_ARCH_CAPABILITIES]);
-                break;
-            }
     }
 
     /*
Signature · 1 line
Eduardo
#19 lore raw

PATCH 1/1 kvm: Use KVM_GET_MSR_INDEX_LIST for MSR_IA32_ARCH_CAPABILITIES support

When writing to guest's MSR_IA32_ARCH_CAPABILITIES, check whether it's supported in the guest using the KVM_GET_MSR_INDEX_LIST ioctl.

Fixes d86f963694df27f11b3681ffd225c9362de1b634
Suggested-by Eduardo Habkost <[email protected]>
Tested-by [email protected]
Signed-off-by Bandan Das <[email protected]>
---
 target/i386/kvm.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)
target/i386/kvm.c +7 -8
index f524e7d929..3d6739a2b2 100644
@@ -95,6 +95,7 @@ static bool has_msr_xss;
 static bool has_msr_spec_ctrl;
 static bool has_msr_virt_ssbd;
 static bool has_msr_smi_count;
+static bool has_msr_arch_capabs;
 
 static uint32_t has_architectural_pmu_version;
 static uint32_t num_architectural_pmu_gp_counters;

@@ -1481,6 +1482,9 @@ static int kvm_get_supported_msrs(KVMState *s)
                 case MSR_VIRT_SSBD:
                     has_msr_virt_ssbd = true;
                     break;
+                case MSR_IA32_ARCH_CAPABILITIES:
+                    has_msr_arch_capabs = true;
+                    break;
                 }
             }
         }

@@ -2002,14 +2006,9 @@ static int kvm_put_msrs(X86CPU *cpu, int level)
 #endif
 
     /* If host supports feature MSR, write down. */
-    if (kvm_feature_msrs) {
-        int i;
-        for (i = 0; i < kvm_feature_msrs->nmsrs; i++)
-            if (kvm_feature_msrs->indices[i] == MSR_IA32_ARCH_CAPABILITIES) {
-                kvm_msr_entry_add(cpu, MSR_IA32_ARCH_CAPABILITIES,
-                              env->features[FEAT_ARCH_CAPABILITIES]);
-                break;
-            }
+    if (has_msr_arch_capabs) {
+        kvm_msr_entry_add(cpu, MSR_IA32_ARCH_CAPABILITIES,
+                          env->features[FEAT_ARCH_CAPABILITIES]);
     }
 
     /*
Signature · 1 line
2.14.5
#20 lore raw

Re: [Qemu-devel] [PATCH] kvm: Use KVM_GET_MSR_INDEX_LIST for MSR_IA32_ARCH_CAPABILITIES support

Quoted 8 lines · Bandan Das

When writing to guest's MSR_IA32_ARCH_CAPABILITIES, check whether it's supported in the guest using the KVM_GET_MSR_INDEX_LIST ioctl.

Fixes d86f963694df27f11b3681ffd225c9362de1b634
Suggested-by Eduardo Habkost <[email protected]>
Tested-by [email protected]
Signed-off-by Bandan Das <[email protected]>

Thanks! Queued for 3.1.

Signature · 1 line
Eduardo
#21 lore raw

Re: [Qemu-devel] [PATCH] kvm: Use KVM_GET_MSR_INDEX_LIST for MSR_IA32_ARCH_CAPABILITIES support

In reply to Bandan Das

Thanks for fixing. Sorry I missed the whole discussion for I hadn't checked my linux.intel.com account for a long time.

Best Regards,
Robert Hoo

Quoted 47 lines

-----Original Message-----
From: Qemu-devel <[email protected]> On Behalf Of Bandan Das
Sent: Monday, November 26, 2018 12:17
To: Eduardo Habkost <[email protected]>; Paolo Bonzini <[email protected]>
Cc: [email protected]; Cole Robinson <[email protected]>; qemu- [email protected]; Laine Stump <[email protected]>; David Alan Gilbert <[email protected]>
Subject: [Qemu-devel] [PATCH] kvm: Use KVM_GET_MSR_INDEX_LIST for MSR_IA32_ARCH_CAPABILITIES support

When writing to guest's MSR_IA32_ARCH_CAPABILITIES, check whether it's supported in the guest using the KVM_GET_MSR_INDEX_LIST ioctl.

Fixes d86f963694df27f11b3681ffd225c9362de1b634
Suggested-by Eduardo Habkost <[email protected]>
Tested-by [email protected]
Signed-off-by Bandan Das <[email protected]>
---
 target/i386/kvm.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)
target/i386/kvm.c index renamed from target/i386/kvm.c +0 -0

f524e7d929..3d6739a2b2 100644

target/i386/kvm.c +4 -0
@@ -95,6 +95,7 @@ static bool has_msr_xss;  static bool has_msr_spec_ctrl;
 static bool has_msr_virt_ssbd;  static bool has_msr_smi_count;
+static bool has_msr_arch_capabs;
 
 static uint32_t has_architectural_pmu_version;  static uint32_t
 num_architectural_pmu_gp_counters;

@@ -1481,6 +1482,9 @@ static int kvm_get_supported_msrs(KVMState *s)
                 case MSR_VIRT_SSBD:
                     has_msr_virt_ssbd = true;
                     break;
+                case MSR_IA32_ARCH_CAPABILITIES:
+                    has_msr_arch_capabs = true;
+                    break;
                 }
             }
         }

@@ -2002,14 +2006,9 @@ static int kvm_put_msrs(X86CPU *cpu, int level)
 #endif

target/i386/kvm.c static int kvm_put_msrs(X86CPU *cpu, int level) · line 2009

Quoted 10 lines
target/i386/kvm.c +1 -8
     /* If host supports feature MSR, write down. */
-    if (kvm_feature_msrs) {
-        int i;
-        for (i = 0; i < kvm_feature_msrs->nmsrs; i++)
-            if (kvm_feature_msrs->indices[i] == MSR_IA32_ARCH_CAPABILITIES) {
-                kvm_msr_entry_add(cpu, MSR_IA32_ARCH_CAPABILITIES,
-                              env->features[FEAT_ARCH_CAPABILITIES]);
-                break;
-            }
+    if (has_msr_arch_capabs) {

[Robert Hoo]
Why not as your original "if (kvm_arch_get_supported_msr_feature(kvm_state, MSR_IA32_ARCH_CAPABILITIES))"? checking if there is the MSR feature?

Quoted 8 lines
target/i386/kvm.c +2 -1
+        kvm_msr_entry_add(cpu, MSR_IA32_ARCH_CAPABILITIES,
+                          env->features[FEAT_ARCH_CAPABILITIES]);
     }
 
     /*
--

2.14.5