[PATCH 1/2] KVM: introduce __vmx_flush_tlb to handle specific vpid

[PATCH 1/2] KVM: introduce __vmx_flush_tlb to handle specific vpid

[Wanpeng Li]

Introduce __vmx_flush_tlb() to handle specific vpid.

Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.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();
 }
@@ -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);
 }
 
 /*
-- 
1.9.1

Re: [PATCH 1/2] KVM: introduce __vmx_flush_tlb to handle specific vpid

[Bandan Das]

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

> Introduce __vmx_flush_tlb() to handle specific vpid.
>
> Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.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);
>  }
>  
>  /*

Re: [PATCH 1/2] KVM: introduce __vmx_flush_tlb to handle specific vpid

[Wanpeng Li]

On 9/25/15 12:12 AM, Bandan Das wrote:
> Wanpeng Li <wanpeng.li@hotmail.com> writes:
>
>> Introduce __vmx_flush_tlb() to handle specific vpid.
>>
>> Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.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.

Indeed, however, there's no easy way to handle the w/o single 
invalidation case, we can improve it if you have any idea, otherwise, it 
can be left to further optimization. :-)

Regards,
Wanpeng Li

Re: [PATCH 1/2] KVM: introduce __vmx_flush_tlb to handle specific vpid

[Paolo Bonzini]

On 24/09/2015 18:12, Bandan Das wrote:
> 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.

It's not a great thing but it's already what happens if you do a global
INVEPT (it calls vmx_flush_tlb, which results in a global INVVPID if the
single-context variant is not supported).

Even without nested virt a single guest could slow down all other guests
just by triggering frequent TLB flushes (e.g. by moving around a ROM BAR
thousands of times per second).

It would help to know _which_ processors actually don't support
single-context INVVPIDs...

Paolo