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Re: [Qemu-devel] [PATCH 3/4] KVM/X86: Enable Intel MPX for guest
From: |
Liu, Jinsong |
Subject: |
Re: [Qemu-devel] [PATCH 3/4] KVM/X86: Enable Intel MPX for guest |
Date: |
Fri, 29 Nov 2013 14:52:50 +0000 |
Paolo Bonzini wrote:
>> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
>> index a8ce117..e30d4ce 100644
>> --- a/arch/x86/kvm/cpuid.c
>> +++ b/arch/x86/kvm/cpuid.c
>> @@ -75,7 +75,7 @@ void kvm_update_cpuid(struct kvm_vcpu *vcpu)
>> (best->eax | ((u64)best->edx << 32)) &
>> host_xcr0 & KVM_SUPPORTED_XCR0;
>> vcpu->arch.guest_xstate_size = best->ebx =
>> - xstate_required_size(vcpu->arch.guest_supported_xcr0);
>> + xstate_required_size(vcpu->arch.xcr0);
>> }
>>
>> kvm_pmu_cpuid_update(vcpu);
>> ...
>> kvm_put_guest_xcr0(vcpu);
>> vcpu->arch.xcr0 = xcr0;
>> +
>> + if ((xcr0 ^ old_xcr0) & XSTATE_EXTEND_MASK)
>> + kvm_update_cpuid(vcpu);
>> +
>> return 0;
>> }
>
> These hunks should be part of the previous patch.
>
>> @@ -5960,6 +5967,9 @@ static int vcpu_enter_guest(struct kvm_vcpu
>> *vcpu) preempt_disable();
>>
>> kvm_x86_ops->prepare_guest_switch(vcpu);
>> + if (kvm_read_cr4_bits(vcpu, X86_CR4_OSXSAVE) &&
>
> Shouldn't be necessary, setting xcr0 fails unless OSXSAVE=1.
>
>> + (vcpu->arch.xcr0 & (u64)(XSTATE_BNDREGS | XSTATE_BNDCSR)))
>> + kvm_x86_ops->fpu_activate(vcpu);
>
> Can you explain this?
No, in fact I'm also some wondering about it, but per it has been tested, I
didn't update this code.
I will double check and drop it if need (or, maybe Xudong can elaborate more?)
Thanks,
Jinsong
>
>> if (vcpu->fpu_active)
>> kvm_load_guest_fpu(vcpu);
>> kvm_load_guest_xcr0(vcpu);
>> diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
>> index 587fb9e..985e40e 100644
>> --- a/arch/x86/kvm/x86.h
>> +++ b/arch/x86/kvm/x86.h
>> @@ -122,7 +122,8 @@ int kvm_write_guest_virt_system(struct
>> x86_emulate_ctxt *ctxt, gva_t addr, void *val, unsigned int bytes,
>> struct x86_exception *exception);
>>
>> -#define KVM_SUPPORTED_XCR0 (XSTATE_FP | XSTATE_SSE | XSTATE_YMM)
>> +#define KVM_SUPPORTED_XCR0 (XSTATE_FP | XSTATE_SSE | XSTATE_YMM \
>> + | XSTATE_BNDREGS | XSTATE_BNDCSR)
>> extern u64 host_xcr0;
>>
>> extern struct static_key kvm_no_apic_vcpu;
>>
>
> Otherwise looks straightforward.
Thanks, will update per your comments.