1. Patchew
  2. linux
  3. View series

[tip: perf/core] kvm: x86/cpuid: Fix CPUID leaf 0xA

tip-bot2 for Sandipan Das posted 1 patch 4 years, 1 month ago
There is a newer version of this series
arch/x86/kvm/cpuid.c | 6 ++++++
1 file changed, 6 insertions(+)
[tip: perf/core] kvm: x86/cpuid: Fix CPUID leaf 0xA
Posted by tip-bot2 for Sandipan Das 4 years, 1 month ago 
The following commit has been merged into the perf/core branch of tip:

Commit-ID:     fafd15ab6dc1fdfff66908e6d9231b124e1875cf
Gitweb:        https://git.kernel.org/tip/fafd15ab6dc1fdfff66908e6d9231b124e1875cf
Author:        Sandipan Das <sandipan.das@amd.com>
AuthorDate:    Thu, 21 Apr 2022 11:16:59 +05:30
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Fri, 29 Apr 2022 11:06:27 +02:00

kvm: x86/cpuid: Fix CPUID leaf 0xA

On some x86 processors, CPUID leaf 0xA provides information
on Architectural Performance Monitoring features. It
advertises a PMU version which Qemu uses to determine the
availability of additional MSRs to manage the PMCs.

Upon receiving a KVM_GET_SUPPORTED_CPUID ioctl request for
the same, the kernel constructs return values based on the
x86_pmu_capability irrespective of the vendor.

This leaf and the additional MSRs are not supported on AMD
processors. If PerfMonV2 is detected, the PMU version is
set to 2 and guest startup breaks because of an attempt to
access a non-existent MSR. Return zeros to avoid this.

Fixes: a6c06ed1a60a ("KVM: Expose the architectural performance monitoring CPUID leaf")
Reported-by: Vasant Hegde <vasant.hegde@amd.com>
Signed-off-by: Sandipan Das <sandipan.das@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/54bc7fe4cadf6bdef823bab1fba43d4891d2e1a9.1650515382.git.sandipan.das@amd.com
---
 arch/x86/kvm/cpuid.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index b24ca7f..ae1d963 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -887,6 +887,12 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
 		union cpuid10_eax eax;
 		union cpuid10_edx edx;
 
+		if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
+		    boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) {
+			entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
+			break;
+		}
+
 		perf_get_x86_pmu_capability(&cap);
 
 		/*
Re: [tip: perf/core] kvm: x86/cpuid: Fix CPUID leaf 0xA
Posted by Borislav Petkov 4 years, 1 month ago 
On Fri, Apr 29, 2022 at 08:28:48PM -0000, tip-bot2 for Sandipan Das wrote:
> The following commit has been merged into the perf/core branch of tip:
> 
> Commit-ID:     fafd15ab6dc1fdfff66908e6d9231b124e1875cf
> Gitweb:        https://git.kernel.org/tip/fafd15ab6dc1fdfff66908e6d9231b124e1875cf
> Author:        Sandipan Das <sandipan.das@amd.com>
> AuthorDate:    Thu, 21 Apr 2022 11:16:59 +05:30
> Committer:     Peter Zijlstra <peterz@infradead.org>
> CommitterDate: Fri, 29 Apr 2022 11:06:27 +02:00
> 
> kvm: x86/cpuid: Fix CPUID leaf 0xA
> 
> On some x86 processors, CPUID leaf 0xA provides information
> on Architectural Performance Monitoring features. It
> advertises a PMU version which Qemu uses to determine the
> availability of additional MSRs to manage the PMCs.
> 
> Upon receiving a KVM_GET_SUPPORTED_CPUID ioctl request for
> the same, the kernel constructs return values based on the
> x86_pmu_capability irrespective of the vendor.
> 
> This leaf and the additional MSRs are not supported on AMD
> processors. If PerfMonV2 is detected, the PMU version is
> set to 2 and guest startup breaks because of an attempt to
> access a non-existent MSR. Return zeros to avoid this.
> 
> Fixes: a6c06ed1a60a ("KVM: Expose the architectural performance monitoring CPUID leaf")
> Reported-by: Vasant Hegde <vasant.hegde@amd.com>
> Signed-off-by: Sandipan Das <sandipan.das@amd.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Link: https://lkml.kernel.org/r/54bc7fe4cadf6bdef823bab1fba43d4891d2e1a9.1650515382.git.sandipan.das@amd.com
> ---
>  arch/x86/kvm/cpuid.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index b24ca7f..ae1d963 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -887,6 +887,12 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
>  		union cpuid10_eax eax;
>  		union cpuid10_edx edx;
>  
> +		if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
> +		    boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) {
> +			entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
> +			break;
> +		}
> +

This is all fine and dandy but this patch in tip conflicts with the very
similar patch of yours:

  5a1bde46f98b ("kvm: x86/cpuid: Only provide CPUID leaf 0xA if host has architectural PMU")

which is already upstream.

So which is it? Should we zap this version in tip instead?

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette
Re: [tip: perf/core] kvm: x86/cpuid: Fix CPUID leaf 0xA
Posted by Sandipan Das 4 years, 1 month ago 
Hi Boris,

On 5/9/2022 10:54 PM, Borislav Petkov wrote:
> On Fri, Apr 29, 2022 at 08:28:48PM -0000, tip-bot2 for Sandipan Das wrote:
>> The following commit has been merged into the perf/core branch of tip:
>>
>> Commit-ID:     fafd15ab6dc1fdfff66908e6d9231b124e1875cf
>> Gitweb:        https://git.kernel.org/tip/fafd15ab6dc1fdfff66908e6d9231b124e1875cf
>> Author:        Sandipan Das <sandipan.das@amd.com>
>> AuthorDate:    Thu, 21 Apr 2022 11:16:59 +05:30
>> Committer:     Peter Zijlstra <peterz@infradead.org>
>> CommitterDate: Fri, 29 Apr 2022 11:06:27 +02:00
>>
>> kvm: x86/cpuid: Fix CPUID leaf 0xA
>>
>> On some x86 processors, CPUID leaf 0xA provides information
>> on Architectural Performance Monitoring features. It
>> advertises a PMU version which Qemu uses to determine the
>> availability of additional MSRs to manage the PMCs.
>>
>> Upon receiving a KVM_GET_SUPPORTED_CPUID ioctl request for
>> the same, the kernel constructs return values based on the
>> x86_pmu_capability irrespective of the vendor.
>>
>> This leaf and the additional MSRs are not supported on AMD
>> processors. If PerfMonV2 is detected, the PMU version is
>> set to 2 and guest startup breaks because of an attempt to
>> access a non-existent MSR. Return zeros to avoid this.
>>
>> Fixes: a6c06ed1a60a ("KVM: Expose the architectural performance monitoring CPUID leaf")
>> Reported-by: Vasant Hegde <vasant.hegde@amd.com>
>> Signed-off-by: Sandipan Das <sandipan.das@amd.com>
>> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
>> Link: https://lkml.kernel.org/r/54bc7fe4cadf6bdef823bab1fba43d4891d2e1a9.1650515382.git.sandipan.das@amd.com
>> ---
>>  arch/x86/kvm/cpuid.c | 6 ++++++
>>  1 file changed, 6 insertions(+)
>>
>> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
>> index b24ca7f..ae1d963 100644
>> --- a/arch/x86/kvm/cpuid.c
>> +++ b/arch/x86/kvm/cpuid.c
>> @@ -887,6 +887,12 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
>>  		union cpuid10_eax eax;
>>  		union cpuid10_edx edx;
>>  
>> +		if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
>> +		    boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) {
>> +			entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
>> +			break;
>> +		}
>> +
> 
> This is all fine and dandy but this patch in tip conflicts with the very
> similar patch of yours:
> 
>   5a1bde46f98b ("kvm: x86/cpuid: Only provide CPUID leaf 0xA if host has architectural PMU")
> 
> which is already upstream.
> 
> So which is it? Should we zap this version in tip instead?
> 

Please remove this patch and keep commit 5a1bde46f98b instead.

- Sandipan
Re: [tip: perf/core] kvm: x86/cpuid: Fix CPUID leaf 0xA
Posted by Peter Zijlstra 4 years, 1 month ago 
On Tue, May 10, 2022 at 10:29:34AM +0530, Sandipan Das wrote:
> > So which is it? Should we zap this version in tip instead?

I made it go away.

Patchew 2.1-devel-ea86937

© 2016 - 2026 Red Hat, Inc.