always report x2apic as supported feature
PATCH 1/1 always report x2apic as supported feature
We emulate x2apic in software, so host support is not required.
arch/x86/kvm/x86.c +3 -0
@@ -1497,6 +1497,9 @@ static void do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,case 1 : entry->edx &= kvm_supported_word0_x86_features; entry->ecx &= kvm_supported_word4_x86_features; +/* we support x2apic emulation even if host does not support +it since we emulate x2apic in software */ + entry->ecx |=F (X2APIC );break ;/* function 2 entries are STATEFUL. That is, repeated cpuid commands * may return different values. This forces us to get_cpu() before
--
Gleb.
Avi Kivity
AppliedQuoted 3 lines · Gleb Natapov
We emulate x2apic in software, so host support is not required.
Applied, thanks.
Signature · 1 line
error compiling committee.c: too many arguments to function
Quoted 18 lines · Gleb Natapov
We emulate x2apic in software, so host support is not required.
Signed-off-by Gleb Natapov <[email protected]>arch/x86/kvm/x86.c +3
-1@@ -1497,6 +1497,9 @@ static void do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,case 1 : entry->edx &= kvm_supported_word0_x86_features; entry->ecx &= kvm_supported_word4_x86_features; +/* we support x2apic emulation even if host does not support +it since we emulate x2apic in software */ + entry->ecx |=F (X2APIC );break ;/* function 2 entries are STATEFUL. That is, repeated cpuid commands * may return different values. This forces us to get_cpu() before --
Quoted 1 line
Gleb.
What if you have an older host that does not support emulate x2apic?
Quoted 14 lines · On Thursday 16 July 2009 07:01:30 Marcelo Tosatti wrote:
Quoted 13 lines · Gleb Natapov
We emulate x2apic in software, so host support is not required.
Signed-off-by Gleb Natapov <[email protected]>arch/x86/kvm/x86.c +2
-0@@ -1497,6 +1497,9 @@ static void do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function, case 1: entry->edx &= kvm_supported_word0_x86_features; entry->ecx &= kvm_supported_word4_x86_features; +/* we support x2apic emulation even if host does not support +it since we emulate x2apic in software */
Quoted 8 lines
Quoted 6 lines
arch/x86/kvm/x86.c +1
-1+ entry->ecx |=F (X2APIC );break ;/* function 2 entries are STATEFUL. That is, repeated cpuid commands * may return different values. This forces us to get_cpu() before -- Gleb.
What if you have an older host that does not support emulate x2apic?
Due to interrupt remapping can't be enabled with KVM now, I think older host would just ignore this info... (The new one can work without interrupt remapping with KVM).
By the way, I saw X2APIC in host supported CPUID feature list(1.ecx), which I don't think it's very properly. Host x2apic feature have nothing to do with KVM, we do the emulation all the way. I suggest to remove the mask for host, and give a comment that we would emulate all x2apic behaviour here, rather than "even if", which I think it's a little misleading.
Signature · 2 lines
regards Yang, Sheng
Quoted 24 lines · Sheng Yang
Quoted 14 lines · On Thursday 16 July 2009 07:01:30 Marcelo Tosatti wrote:
Quoted 13 lines · Gleb Natapov
We emulate x2apic in software, so host support is not required.
Signed-off-by Gleb Natapov <[email protected]>arch/x86/kvm/x86.c +2
-0@@ -1497,6 +1497,9 @@ static void do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function, case 1: entry->edx &= kvm_supported_word0_x86_features; entry->ecx &= kvm_supported_word4_x86_features; +/* we support x2apic emulation even if host does not support +it since we emulate x2apic in software */ Quoted 8 lines
Quoted 6 lines
arch/x86/kvm/x86.c +1
-1+ entry->ecx |=F (X2APIC );break ;/* function 2 entries are STATEFUL. That is, repeated cpuid commands * may return different values. This forces us to get_cpu() before -- Gleb.
What if you have an older host that does not support emulate x2apic?
Quoted 5 lines
Due to interrupt remapping can't be enabled with KVM now, I think older host would just ignore this info... (The new one can work without interrupt remapping with KVM).
By the way, I saw X2APIC in host supported CPUID feature list(1.ecx), which I
Where have you seen it? If you mean kvm_supported_word4_x86_features then it is not what is supported by the host, but what is supported by KVM. Host unsupported bits are dropped from there before reporting to userspace. That is why this patch what necessary.
Quoted 8 lines
don't think it's very properly. Host x2apic feature have nothing to do with KVM, we do the emulation all the way. I suggest to remove the mask for host, and give a comment that we would emulate all x2apic behaviour here, rather than "even if", which I think it's a little misleading.
Signature · 2 lines
regards Yang, Sheng
--
Gleb.
Quoted 29 lines · On Thursday 16 July 2009 14:00:15 Gleb Natapov wrote:
Quoted 28 lines · Sheng Yang
Quoted 14 lines · On Thursday 16 July 2009 07:01:30 Marcelo Tosatti wrote:
Quoted 13 lines · Gleb Natapov
We emulate x2apic in software, so host support is not required.
Signed-off-by Gleb Natapov <[email protected]>arch/x86/kvm/x86.c +0
-0@@ -1497,6 +1497,9 @@ static void do_cpuid_ent(struct
kvm_cpuid_entry2*entry, u32 function, case 1:arch/x86/kvm/x86.c +2
-0entry->edx &= kvm_supported_word0_x86_features; entry->ecx &= kvm_supported_word4_x86_features; +/* we support x2apic emulation even if host does not support +it since we emulate x2apic in software */ Quoted 8 lines
Quoted 6 lines
arch/x86/kvm/x86.c +1
-0+ entry->ecx |=F (X2APIC );break ;/* function 2 entries are STATEFUL. That is, repeated cpuid commands * may return different values. This forces us to
get_cpu()before --
Gleb.What if you have an older host that does not support emulate x2apic?
Due to interrupt remapping can't be enabled with KVM now, I think older host would just ignore this info... (The new one can work without interrupt remapping with KVM).
Quoted 7 lines
Quoted 2 lines
By the way, I saw X2APIC in host supported CPUID feature list(1.ecx), which I
Where have you seen it? If you mean
kvm_supported_word4_x86_featuresthen it is not what is supported by the host, but what is supported by KVM. Host unsupported bits are dropped from there before reporting to userspace. That is why this patch what necessary.
Yes, that's what I mean. x2apic feature needn't judged by host feature, we can always set the bit to support it, no need for a filter. I think put it in the kvm_supported_word4_x86_features is a little misleading means that KVM support it through host feature rather than emulation.
Anyway, not a big deal.
Signature · 2 lines
regards Yang, Sheng
Quoted 12 lines
Quoted 9 lines
don't think it's very properly. Host x2apic feature have nothing to do with KVM, we do the emulation all the way. I suggest to remove the mask for host, and give a comment that we would emulate all x2apic behaviour here, rather than "even if", which I think it's a little misleading.
--
regards
Yang, Sheng--
Gleb.
Quoted 38 lines · Sheng Yang
Quoted 29 lines · On Thursday 16 July 2009 14:00:15 Gleb Natapov wrote:
Quoted 28 lines · Sheng Yang
Quoted 14 lines · On Thursday 16 July 2009 07:01:30 Marcelo Tosatti wrote:
Quoted 13 lines · Gleb Natapov
We emulate x2apic in software, so host support is not required.
Signed-off-by Gleb Natapov <[email protected]>arch/x86/kvm/x86.c +0
-0@@ -1497,6 +1497,9 @@ static void do_cpuid_ent(struct
kvm_cpuid_entry2*entry, u32 function, case 1:arch/x86/kvm/x86.c +2
-0entry->edx &= kvm_supported_word0_x86_features; entry->ecx &= kvm_supported_word4_x86_features; +/* we support x2apic emulation even if host does not support +it since we emulate x2apic in software */ Quoted 8 lines
Quoted 6 lines
arch/x86/kvm/x86.c +1
-0+ entry->ecx |=F (X2APIC );break ;/* function 2 entries are STATEFUL. That is, repeated cpuid commands * may return different values. This forces us to
get_cpu()before --
Gleb.What if you have an older host that does not support emulate x2apic?
Due to interrupt remapping can't be enabled with KVM now, I think older host would just ignore this info... (The new one can work without interrupt remapping with KVM).
Quoted 7 lines
Quoted 2 lines
By the way, I saw X2APIC in host supported CPUID feature list(1.ecx), which I
Where have you seen it? If you mean
kvm_supported_word4_x86_featuresthen it is not what is supported by the host, but what is supported by KVM. Host unsupported bits are dropped from there before reporting to userspace. That is why this patch what necessary.
Quoted 5 lines
Yes, that's what I mean. x2apic feature needn't judged by host feature, we can always set the bit to support it, no need for a filter. I think put it in the
kvm_supported_word4_x86_featuresis a little misleading means that KVM support it through host feature rather than emulation.
Yeah, I put it there initially since I misunderstood how things work and thought that it will be reported to userspace (and usercpace had a bug that prevented me from discovering the problem).
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Gleb.