Re: [PATCH v2 09/15] KVM: x86: Refine the matching and clearing logic for supported_xss

["Yang, Weijiang" <weijiang.yang@intel.com>]

On 1/28/2023 5:46 AM, Sean Christopherson wrote:
> On Thu, Nov 24, 2022, Yang Weijiang wrote:
>> From: Paolo Bonzini <pbonzini@redhat.com>
>>
>> Refine the code path of the existing clearing of supported_xss in this way:
>> initialize the supported_xss with the filter of KVM_SUPPORTED_XSS mask and
>> update its value in a bit clear manner (rather than bit setting).
>>
>> Suggested-by: Sean Christopherson <seanjc@google.com>
>> Signed-off-by: Like Xu <like.xu@linux.intel.com>
>> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>> Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
>> ---
>>   arch/x86/kvm/vmx/vmx.c | 5 +++--
>>   arch/x86/kvm/x86.c     | 6 +++++-
>>   2 files changed, 8 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
>> index 9bd52ad3bbf4..2ab4c33b5008 100644
>> --- a/arch/x86/kvm/vmx/vmx.c
>> +++ b/arch/x86/kvm/vmx/vmx.c
>> @@ -7738,9 +7738,10 @@ static __init void vmx_set_cpu_caps(void)
>>   		kvm_cpu_cap_set(X86_FEATURE_UMIP);
>>   
>>   	/* CPUID 0xD.1 */
>> -	kvm_caps.supported_xss = 0;
> This needs to stay until VMX actually supports something.

Will modify this patch.


>
>> -	if (!cpu_has_vmx_xsaves())
>> +	if (!cpu_has_vmx_xsaves()) {
>>   		kvm_cpu_cap_clear(X86_FEATURE_XSAVES);
>> +		kvm_caps.supported_xss = 0;
> This is already handled in common KVM.
>
>> +	}
>>   
>>   	/* CPUID 0x80000001 and 0x7 (RDPID) */
>>   	if (!cpu_has_vmx_rdtscp()) {
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> index 74c858eaa1ea..889be0c9176d 100644
>> --- a/arch/x86/kvm/x86.c
>> +++ b/arch/x86/kvm/x86.c
>> @@ -217,6 +217,8 @@ static struct kvm_user_return_msrs __percpu *user_return_msrs;
>>   				| XFEATURE_MASK_BNDCSR | XFEATURE_MASK_AVX512 \
>>   				| XFEATURE_MASK_PKRU | XFEATURE_MASK_XTILE)
>>   
>> +#define KVM_SUPPORTED_XSS     0
>> +
>>   u64 __read_mostly host_efer;
>>   EXPORT_SYMBOL_GPL(host_efer);
>>   
>> @@ -11999,8 +12001,10 @@ int kvm_arch_hardware_setup(void *opaque)
>>   
>>   	rdmsrl_safe(MSR_EFER, &host_efer);
>>   
>> -	if (boot_cpu_has(X86_FEATURE_XSAVES))
>> +	if (boot_cpu_has(X86_FEATURE_XSAVES)) {
>>   		rdmsrl(MSR_IA32_XSS, host_xss);
>> +		kvm_caps.supported_xss = host_xss & KVM_SUPPORTED_XSS;
>> +	}
>>   
>>   	kvm_init_pmu_capability();
>>   
>> -- 
>> 2.27.0
>>