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target-i386: Enabling IA32_TSC_ADJUST for Qemu KVM guest VMs

PATCH Superseded Will Auld 2 participants 2 messages Nov 27, 2012 KVM

v4 of 5 Superseded Latest is v5 →

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Will Auld

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PATCH v4 1/1 target-i386: Enabling IA32_TSC_ADJUST for Qemu KVM guest VMs

CPUID.7.0.EBX[1]=1 indicates IA32_TSC_ADJUST MSR 0x3b is supported

Basic design is to emulate the MSR by allowing reads and writes to the hypervisor vcpu specific locations to store the value of the emulated MSRs. In this way the IA32_TSC_ADJUST value will be included in all reads to the TSC MSR whether through rdmsr or rdtsc.

As this is a new MSR that the guest may access and modify its value needs to be migrated along with the other MRSs. The changes here are specifically for recognizing when IA32_TSC_ADJUST is enabled in CPUID and code added for migrating its value.

Signed-off-by Will Auld <[email protected]>
---
 target-i386/cpu.h     |  2 ++
 target-i386/kvm.c     | 14 ++++++++++++++
 target-i386/machine.c | 21 +++++++++++++++++++++
 3 files changed, 37 insertions(+)
target-i386/cpu.h +2 -0
index aabf993..9dedaa6 100644
@@ -284,6 +284,7 @@
 #define MSR_IA32_APICBASE_BSP           (1<<8)
 #define MSR_IA32_APICBASE_ENABLE        (1<<11)
 #define MSR_IA32_APICBASE_BASE          (0xfffff<<12)
+#define MSR_TSC_ADJUST			0x0000003b
 #define MSR_IA32_TSCDEADLINE            0x6e0
 
 #define MSR_MTRRcap			0xfe

@@ -701,6 +702,7 @@ typedef struct CPUX86State {
     uint64_t async_pf_en_msr;
 
     uint64_t tsc;
+    uint64_t tsc_adjust;
     uint64_t tsc_deadline;
 
     uint64_t mcg_status;
target-i386/kvm.c +14 -0
index 696b14a..6d2a061 100644
@@ -61,6 +61,7 @@ const KVMCapabilityInfo kvm_arch_required_capabilities[] = {
 
 static bool has_msr_star;
 static bool has_msr_hsave_pa;
+static bool has_msr_tsc_adjust;
 static bool has_msr_tsc_deadline;
 static bool has_msr_async_pf_en;
 static bool has_msr_misc_enable;

@@ -641,6 +642,10 @@ static int kvm_get_supported_msrs(KVMState *s)
                     has_msr_hsave_pa = true;
                     continue;
                 }
+		if (kvm_msr_list->indices[i] == MSR_TSC_ADJUST) {
+		    has_msr_tsc_adjust = true;
+		    continue;
+		}
                 if (kvm_msr_list->indices[i] == MSR_IA32_TSCDEADLINE) {
                     has_msr_tsc_deadline = true;
                     continue;

@@ -978,6 +983,9 @@ static int kvm_put_msrs(CPUX86State *env, int level)
     if (has_msr_hsave_pa) {
         kvm_msr_entry_set(&msrs[n++], MSR_VM_HSAVE_PA, env->vm_hsave);
     }
+    if (has_msr_tsc_adjust) {
+	kvm_msr_entry_set(&msrs[n++], MSR_TSC_ADJUST, env->tsc_adjust);
+    }
     if (has_msr_tsc_deadline) {
         kvm_msr_entry_set(&msrs[n++], MSR_IA32_TSCDEADLINE, env->tsc_deadline);
     }

@@ -1234,6 +1242,9 @@ static int kvm_get_msrs(CPUX86State *env)
     if (has_msr_hsave_pa) {
         msrs[n++].index = MSR_VM_HSAVE_PA;
     }
+    if (has_msr_tsc_adjust) {
+	msrs[n++].index = MSR_TSC_ADJUST;
+    }
     if (has_msr_tsc_deadline) {
         msrs[n++].index = MSR_IA32_TSCDEADLINE;
     }

@@ -1308,6 +1319,9 @@ static int kvm_get_msrs(CPUX86State *env)
         case MSR_IA32_TSC:
             env->tsc = msrs[i].data;
             break;
+	case MSR_TSC_ADJUST:
+	    env->tsc_adjust = msrs[i].data;
+	    break;
         case MSR_IA32_TSCDEADLINE:
             env->tsc_deadline = msrs[i].data;
             break;
target-i386/machine.c +21 -0
index a8be058..df3f779 100644
@@ -310,6 +310,24 @@ static const VMStateDescription vmstate_fpop_ip_dp = {
     }
 };
 
+static bool tsc_adjust_needed(void *opaque)
+{
+    CPUX86State *env = opaque;
+
+    return env->tsc_adjust != 0;
+}
+
+static const VMStateDescription vmstate_msr_tsc_adjust = {
+    .name = "cpu/msr_tsc_adjust",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .minimum_version_id_old = 1,
+    .fields      = (VMStateField []) {
+        VMSTATE_UINT64(tsc_adjust, CPUX86State),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
 static bool tscdeadline_needed(void *opaque)
 {
     CPUX86State *env = opaque;

@@ -457,6 +475,9 @@ static const VMStateDescription vmstate_cpu = {
             .vmsd = &vmstate_fpop_ip_dp,
             .needed = fpop_ip_dp_needed,
         }, {
+            .vmsd = &vmstate_msr_tsc_adjust,
+            .needed = tsc_adjust_needed,
+        }, {
             .vmsd = &vmstate_msr_tscdeadline,
             .needed = tscdeadline_needed,
         }, {
Signature · 1 line
1.8.0.rc0
#1 lore raw

Am 27.11.2012 03:29, schrieb Will Auld:

Quoted 7 lines

CPUID.7.0.EBX[1]=1 indicates IA32_TSC_ADJUST MSR 0x3b is supported

Basic design is to emulate the MSR by allowing reads and writes to the hypervisor vcpu specific locations to store the value of the emulated MSRs. In this way the IA32_TSC_ADJUST value will be included in all reads to the TSC MSR whether through rdmsr or rdtsc.

Quoted 6 lines

As this is a new MSR that the guest may access and modify its value needs to be migrated along with the other MRSs. The changes here are specifically for recognizing when IA32_TSC_ADJUST is enabled in CPUID and code added for migrating its value.

Signed-off-by Will Auld <[email protected]>

Better, but problems remain (not sure about line endings, didn't check before). It seems the tabs got more rather than getting replaced with four spaces. (And QEMU regressed to Qemu.)

For future patches you may find the following helpful to detect formal errors early yourself (git commit --no-verify overrides):
http://blog.vmsplice.net/2011/03/how-to-automatically-run-checkpatchpl.html

Regards,
Andreas

$ scripts/checkpatch.pl ../wauld_tsc_adjust_v4.eml
ERROR: DOS line endings
#129: FILE: target-i386/cpu.h:287:
+#define MSR_TSC_ADJUST^I^I^I0x0000003b^M$

ERROR: code indent should never use tabs
#129: FILE: target-i386/cpu.h:287:
+#define MSR_TSC_ADJUST^I^I^I0x0000003b^M$

ERROR: DOS line endings
[...]

ERROR: code indent should never use tabs
#157: FILE: target-i386/kvm.c:645:
+^I^Iif (kvm_msr_list->indices[i] == MSR_TSC_ADJUST) {^M$

ERROR: DOS line endings
#158: FILE: target-i386/kvm.c:646:
+^I^I has_msr_tsc_adjust = true;^M$

ERROR: code indent should never use tabs
#158: FILE: target-i386/kvm.c:646:
+^I^I has_msr_tsc_adjust = true;^M$

[...]

total: 48 errors, 0 warnings, 91 lines checked

../wauld_tsc_adjust_v4.eml has style problems, please review. [...]

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