Re: [Xen-devel] [PATCH v3 5/9] x86/vvmx: make updating shadow EPTP value more efficient

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 05/10/17 14:04, Sergey Dyasli wrote:
> On Thu, 2017-10-05 at 03:27 -0600, Jan Beulich wrote:
>>>>> On 05.10.17 at 10:18, <sergey.dyasli@xxxxxxxxxx> wrote:
>>> --- a/xen/arch/x86/hvm/vmx/entry.S
>>> +++ b/xen/arch/x86/hvm/vmx/entry.S
>>> @@ -80,7 +80,7 @@ UNLIKELY_END(realmode)
>>>          mov  %rsp,%rdi
>>>          call vmx_vmenter_helper
>>>          cmp  $0,%eax
>>> -        jne .Lvmx_vmentry_restart
>>> +        je .Lvmx_vmentry_restart
>> If you make the function return bool, the cmp above also needs
>> changing (and then preferably to "test %al, %al", in which case
>> it would then also better be "jz" instead of "je").
> Here's the updated delta:
>
> diff --git a/xen/arch/x86/hvm/vmx/entry.S b/xen/arch/x86/hvm/vmx/entry.S
> index 9fb8f89220..47cd674260 100644
> --- a/xen/arch/x86/hvm/vmx/entry.S
> +++ b/xen/arch/x86/hvm/vmx/entry.S
> @@ -79,8 +79,8 @@ UNLIKELY_END(realmode)
>  
>          mov  %rsp,%rdi
>          call vmx_vmenter_helper
> -        cmp  $0,%eax
> -        jne .Lvmx_vmentry_restart
> +        test %al, %al
> +        jz .Lvmx_vmentry_restart
>          mov  VCPU_hvm_guest_cr2(%rbx),%rax
>  
>          pop  %r15
> diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
> index c9a4111267..a5c2bd71cd 100644
> --- a/xen/arch/x86/hvm/vmx/vmx.c
> +++ b/xen/arch/x86/hvm/vmx/vmx.c
> @@ -4197,7 +4197,8 @@ static void lbr_fixup(void)
>          bdw_erratum_bdf14_fixup();
>  }
>  
> -int vmx_vmenter_helper(const struct cpu_user_regs *regs)
> +/* Returns false if the vmentry has to be restarted */
> +bool vmx_vmenter_helper(const struct cpu_user_regs *regs)
>  {
>      struct vcpu *curr = current;
>      u32 new_asid, old_asid;
> @@ -4206,7 +4207,7 @@ int vmx_vmenter_helper(const struct cpu_user_regs *regs)
>  
>      /* Shadow EPTP can't be updated here because irqs are disabled */
>       if ( nestedhvm_vcpu_in_guestmode(curr) && 
> vcpu_nestedhvm(curr).stale_np2m )
> -         return 1;
> +         return false;
>  
>      if ( curr->domain->arch.hvm_domain.pi_ops.do_resume )
>          curr->domain->arch.hvm_domain.pi_ops.do_resume(curr);
> @@ -4269,7 +4270,7 @@ int vmx_vmenter_helper(const struct cpu_user_regs *regs)
>      __vmwrite(GUEST_RSP,    regs->rsp);
>      __vmwrite(GUEST_RFLAGS, regs->rflags | X86_EFLAGS_MBS);
>  
> -    return 0;
> +    return true;
>  }

With this, the whole series is Acked-by: Andrew Cooper
<andrew.cooper3@xxxxxxxxxx>

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