[v2] Fix cross migration issue with missing features: pdcm, arch-capabilities

[RFT PATCH v2 0/2] Fix cross migration issue with missing features: pdcm, arch-capabilities

Paolo Bonzini posted 2 patches 5 days, 4 hours ago

Diff against v1 v1 v2
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Patches applied successfully (tree, apply log)
git fetch https://github.com/patchew-project/qemu tags/patchew/20250923104136.133875-1-pbonzini@redhat.com

Maintainers: Paolo Bonzini <pbonzini@redhat.com>, Richard Henderson <richard.henderson@linaro.org>, Eduardo Habkost <eduardo@habkost.net>, "Michael S. Tsirkin" <mst@redhat.com>, Marcel Apfelbaum <marcel.apfelbaum@gmail.com>, Zhao Liu <zhao1.liu@intel.com>, Marcelo Tosatti <mtosatti@redhat.com>

There is a newer version of this series

target/i386/cpu.h     | 12 ++++++++++++
hw/i386/pc.c          |  2 ++
target/i386/cpu.c     | 32 +++++++++++++++++++++++++++++---
target/i386/kvm/kvm.c |  6 +-----
4 files changed, 44 insertions(+), 8 deletions(-)

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[RFT PATCH v2 0/2] Fix cross migration issue with missing features: pdcm, arch-capabilities

Posted by Paolo Bonzini 5 days, 4 hours ago

Add two compatibility properties to restore legacy behavior of machine types
prior to QEMU 10.1.  Each of them addresses the two changes to CPUID:

- ARCH_CAPABILITIES should not be autoenabled when the CPU model specifies AMD
  as the vendor

- specifying PDCM without PMU now causes an error, instead of being silently
  dropped in cpu_x86_cpuid.

Note, I only tested this lightly.

Paolo

Hector Cao (1):
  target/i386: add compatibility property for pdcm feature

Paolo Bonzini (1):
  target/i386: add compatibility property for arch_capabilities

 target/i386/cpu.h     | 12 ++++++++++++
 hw/i386/pc.c          |  2 ++
 target/i386/cpu.c     | 32 +++++++++++++++++++++++++++++---
 target/i386/kvm/kvm.c |  6 +-----
 4 files changed, 44 insertions(+), 8 deletions(-)

-- 
2.51.0

Re: [RFT PATCH v2 0/2] Fix cross migration issue with missing features: pdcm, arch-capabilities

Posted by Zhao Liu 2 days, 22 hours ago

On Tue, Sep 23, 2025 at 12:41:34PM +0200, Paolo Bonzini wrote:
> Date: Tue, 23 Sep 2025 12:41:34 +0200
> From: Paolo Bonzini <pbonzini@redhat.com>
> Subject: [RFT PATCH v2 0/2] Fix cross migration issue with missing
>  features: pdcm, arch-capabilities
> X-Mailer: git-send-email 2.51.0
> 
> Add two compatibility properties to restore legacy behavior of machine types
> prior to QEMU 10.1.  Each of them addresses the two changes to CPUID:
> 
> - ARCH_CAPABILITIES should not be autoenabled when the CPU model specifies AMD
>   as the vendor
> 
> - specifying PDCM without PMU now causes an error, instead of being silently
>   dropped in cpu_x86_cpuid.
> 
> Note, I only tested this lightly.

Sorry for late.

I found the previous 2 fixes were merged into stable 10.0:

24778b1c7ee7aca9721ed4757b0e0df0c16390f7
3d26cb65c27190e57637644ecf6c96b8c3d246a3

Should stable 10.0 revert these 2 fixes, to ensure migration
compatibility?

(+Michael)

Regards,
Zhao

Re: [RFT PATCH v2 0/2] Fix cross migration issue with missing features: pdcm, arch-capabilities

Posted by Paolo Bonzini 5 hours ago

On 9/25/25 18:17, Zhao Liu wrote:
> On Tue, Sep 23, 2025 at 12:41:34PM +0200, Paolo Bonzini wrote:
>> Date: Tue, 23 Sep 2025 12:41:34 +0200
>> From: Paolo Bonzini <pbonzini@redhat.com>
>> Subject: [RFT PATCH v2 0/2] Fix cross migration issue with missing
>>   features: pdcm, arch-capabilities
>> X-Mailer: git-send-email 2.51.0
>>
>> Add two compatibility properties to restore legacy behavior of machine types
>> prior to QEMU 10.1.  Each of them addresses the two changes to CPUID:
>>
>> - ARCH_CAPABILITIES should not be autoenabled when the CPU model specifies AMD
>>    as the vendor
>>
>> - specifying PDCM without PMU now causes an error, instead of being silently
>>    dropped in cpu_x86_cpuid.
>>
>> Note, I only tested this lightly.
> 
> Sorry for late.
> 
> I found the previous 2 fixes were merged into stable 10.0:
> 
> 24778b1c7ee7aca9721ed4757b0e0df0c16390f7
> 3d26cb65c27190e57637644ecf6c96b8c3d246a3

Yes, thanks for noticing it Zhao.  Because we cannot apply the machine 
type changes to 10.0, those two patches have to be reverted.

Paolo