Re: [Xen-devel] [PATCH 16/27] x86/svm: Improvements using named features

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 01/04/2017 07:39 AM, Andrew Cooper wrote:
> This avoids calling into hvm_cpuid() to obtain information which is directly
> available.  In particular, this avoids the need to overload flag_dr_dirty
> because of hvm_cpuid() being unavailable svm_save_dr()

"unavailabe in" (or from)

>
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> ---
> CC: Jan Beulich <JBeulich@xxxxxxxx>
> CC: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> CC: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
> ---
>  xen/arch/x86/hvm/svm/svm.c | 33 ++++++++-------------------------
>  1 file changed, 8 insertions(+), 25 deletions(-)
>
> diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
> index de20f64..8f6737c 100644
> --- a/xen/arch/x86/hvm/svm/svm.c
> +++ b/xen/arch/x86/hvm/svm/svm.c
> @@ -173,7 +173,7 @@ static void svm_save_dr(struct vcpu *v)
>      v->arch.hvm_vcpu.flag_dr_dirty = 0;
>      vmcb_set_dr_intercepts(vmcb, ~0u);
>  
> -    if ( flag_dr_dirty & 2 )
> +    if ( v->domain->arch.cpuid->extd.dbext )
>      {
>          svm_intercept_msr(v, MSR_AMD64_DR0_ADDRESS_MASK, MSR_INTERCEPT_RW);
>          svm_intercept_msr(v, MSR_AMD64_DR1_ADDRESS_MASK, MSR_INTERCEPT_RW);
> @@ -196,8 +196,6 @@ static void svm_save_dr(struct vcpu *v)
>  
>  static void __restore_debug_registers(struct vmcb_struct *vmcb, struct vcpu 
> *v)
>  {
> -    unsigned int ecx;
> -
>      if ( v->arch.hvm_vcpu.flag_dr_dirty )
>          return;
>  
> @@ -205,8 +203,8 @@ static void __restore_debug_registers(struct vmcb_struct 
> *vmcb, struct vcpu *v)
>      vmcb_set_dr_intercepts(vmcb, 0);
>  
>      ASSERT(v == current);
> -    hvm_cpuid(0x80000001, NULL, NULL, &ecx, NULL);
> -    if ( test_bit(X86_FEATURE_DBEXT & 31, &ecx) )
> +
> +    if ( v->domain->arch.cpuid->extd.dbext )
>      {
>          svm_intercept_msr(v, MSR_AMD64_DR0_ADDRESS_MASK, MSR_INTERCEPT_NONE);
>          svm_intercept_msr(v, MSR_AMD64_DR1_ADDRESS_MASK, MSR_INTERCEPT_NONE);
> @@ -217,9 +215,6 @@ static void __restore_debug_registers(struct vmcb_struct 
> *vmcb, struct vcpu *v)
>          wrmsrl(MSR_AMD64_DR1_ADDRESS_MASK, v->arch.hvm_svm.dr_mask[1]);
>          wrmsrl(MSR_AMD64_DR2_ADDRESS_MASK, v->arch.hvm_svm.dr_mask[2]);
>          wrmsrl(MSR_AMD64_DR3_ADDRESS_MASK, v->arch.hvm_svm.dr_mask[3]);
> -
> -        /* Can't use hvm_cpuid() in svm_save_dr(): v != current. */
> -        v->arch.hvm_vcpu.flag_dr_dirty |= 2;

Should v->arch.hvm_vcpu.flag_dr_dirty be converted to bool then?

-boris


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