Re: [PATCH v2 01/12] KVM: SVM: Add VMCB fields for LBRv2 virtualization

[Shivansh Dhiman <shivansh.dhiman@amd.com>]

On 20-10-26 03:39, Jim Mattson wrote:
> [You don't often get email from jmattson@google.com. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ]
> 
> On Mon, Oct 19, 2026 at 2:06 PM Shivansh Dhiman <shivansh.dhiman@amd.com> wrote:
>>
>> From: Sandipan Das <sandipan.das@amd.com>
>>
>> Define the new VMCB fields that will be used to save and restore the
>> state of the following Last Branch Record Extension Version 2 (LbrExtV2)
>> related MSRs.
>>   * Last Branch Stack Select (MSR 0xc000010e)
>>   * Debug Extension Control (MSR 0xc000010f)
>>   * LBRv2 Branch FROM (MSRs 0xc0010300..0xc001031e)
>>   * LBRv2 Branch To (MSRs 0xc0010301..0xc001031f)
>>
>> Signed-off-by: Sandipan Das <sandipan.das@amd.com>
>> Signed-off-by: Shivansh Dhiman <shivansh.dhiman@amd.com>
>> ---
>>  arch/x86/include/asm/svm.h | 14 +++++++++++---
>>  1 file changed, 11 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h
>> index 83fd49b26a4b..d76844224745 100644
>> --- a/arch/x86/include/asm/svm.h
>> +++ b/arch/x86/include/asm/svm.h
>> @@ -372,8 +372,15 @@ struct vmcb_save_area {
>>         u64 br_to;
>>         u64 last_excp_from;
>>         u64 last_excp_to;
>> -       u8 reserved_0x298[72];
>> +       u64 dbg_extn_cfg;
>> +       u8 reserved_0x2a0[64];
>>         u64 spec_ctrl;          /* Guest version of SPEC_CTRL at 0x2E0 */
>> +       u8 reserved_0x2e8[904];
>> +       struct {
>> +               u64 lbr_stack_from;
>> +               u64 lbr_stack_to;
>> +       } __packed lbr[16];
> 
> Nit: instead of '16', can we hoist the definition of
> SVM_LBR_V2_STACK_SIZE from patch 3 and use that here?

That's a good idea. will do that in next version.

> 
> Reviewed-by: Jim Mattson <jmattson@google.com>

Thanks for reviewing. :)