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

2015-09-25 Thread 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
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Re: [PATCH 1/2] KVM: introduce __vmx_flush_tlb to handle specific vpid

2015-09-24 Thread Wanpeng Li 

On 9/25/15 12:12 AM, Bandan Das wrote:

Wanpeng Li  writes:


Introduce __vmx_flush_tlb() to handle specific vpid.

Signed-off-by: Wanpeng Li 
---
  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
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Re: [PATCH 1/2] KVM: introduce __vmx_flush_tlb to handle specific vpid

2015-09-24 Thread Bandan Das 
Wanpeng Li  writes:

> Introduce __vmx_flush_tlb() to handle specific vpid.
>
> Signed-off-by: Wanpeng Li 
> ---
>  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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[PATCH 1/2] KVM: introduce __vmx_flush_tlb to handle specific vpid

2015-09-23 Thread Wanpeng Li 
Introduce __vmx_flush_tlb() to handle specific vpid.

Signed-off-by: Wanpeng Li 
---
 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

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