linux-kernel - Re: [PATCH 1/2] KVM: introduce __vmx_flush

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Date:	Thu, 24 Sep 2015 12:12:43 -0400
From:	Bandan Das <bsd@...hat.com>
To:	Wanpeng Li <wanpeng.li@...mail.com>
Cc:	Paolo Bonzini <pbonzini@...hat.com>,
	Jan Kiszka <jan.kiszka@...mens.com>,
	Wincy Van <fanwenyi0529@...il.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] KVM: introduce __vmx_flush_tlb to handle specific vpid

Wanpeng Li <wanpeng.li@...mail.com> writes:

> Introduce __vmx_flush_tlb() to handle specific vpid.
>
> Signed-off-by: Wanpeng Li <wanpeng.li@...mail.com>
> ---
>  arch/x86/kvm/vmx.c | 21 +++++++++++++--------
>  1 file changed, 13 insertions(+), 8 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 794c529..7188c5e 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -1343,13 +1343,13 @@ static void loaded_vmcs_clear(struct loaded_vmcs *loaded_vmcs)
>  			 __loaded_vmcs_clear, loaded_vmcs, 1);
>  }
>  
> -static inline void vpid_sync_vcpu_single(struct vcpu_vmx *vmx)
> +static inline void vpid_sync_vcpu_single(int vpid)
>  {
> -	if (vmx->vpid == 0)
> +	if (vpid == 0)
>  		return;
>  
>  	if (cpu_has_vmx_invvpid_single())
> -		__invvpid(VMX_VPID_EXTENT_SINGLE_CONTEXT, vmx->vpid, 0);
> +		__invvpid(VMX_VPID_EXTENT_SINGLE_CONTEXT, vpid, 0);
>  }
>  
>  static inline void vpid_sync_vcpu_global(void)
> @@ -1358,10 +1358,10 @@ static inline void vpid_sync_vcpu_global(void)
>  		__invvpid(VMX_VPID_EXTENT_ALL_CONTEXT, 0, 0);
>  }
>  
> -static inline void vpid_sync_context(struct vcpu_vmx *vmx)
> +static inline void vpid_sync_context(int vpid)
>  {
>  	if (cpu_has_vmx_invvpid_single())
> -		vpid_sync_vcpu_single(vmx);
> +		vpid_sync_vcpu_single(vpid);
>  	else
>  		vpid_sync_vcpu_global();
>  }

Not sure myself what's the right thing to do but this may be undesirable
in a nested environment. Assuming the processor supports global invalidation
only, this seems like a easy way for the nested guest to invalidate *all*
mappings - even the L1 specific mappings.


> @@ -3450,9 +3450,9 @@ static void exit_lmode(struct kvm_vcpu *vcpu)
>  
>  #endif
>  
> -static void vmx_flush_tlb(struct kvm_vcpu *vcpu)
> +static inline void __vmx_flush_tlb(struct kvm_vcpu *vcpu, int vpid)
>  {
> -	vpid_sync_context(to_vmx(vcpu));
> +	vpid_sync_context(vpid);
>  	if (enable_ept) {
>  		if (!VALID_PAGE(vcpu->arch.mmu.root_hpa))
>  			return;
> @@ -3460,6 +3460,11 @@ static void vmx_flush_tlb(struct kvm_vcpu *vcpu)
>  	}
>  }
>  
> +static void vmx_flush_tlb(struct kvm_vcpu *vcpu)
> +{
> +	__vmx_flush_tlb(vcpu, to_vmx(vcpu)->vpid);
> +}
> +
>  static void vmx_decache_cr0_guest_bits(struct kvm_vcpu *vcpu)
>  {
>  	ulong cr0_guest_owned_bits = vcpu->arch.cr0_guest_owned_bits;
> @@ -4795,7 +4800,7 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
>  	vmx_fpu_activate(vcpu);
>  	update_exception_bitmap(vcpu);
>  
> -	vpid_sync_context(vmx);
> +	vpid_sync_context(vmx->vpid);
>  }
>  
>  /*
--
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