[PATCH][v2 0/3] Some MMU related fix/clean up

[PATCH][v2 0/3] Some MMU related fix/clean up

[Sheng Yang]

Sheng Yang (3):
  KVM: x86: Check LMA bit before set_efer
  KVM: Clean up duplicate assignment
  VMX: x86: Only reset MMU when necessary

 arch/x86/kvm/mmu.c |    5 ++---
 arch/x86/kvm/x86.c |   22 ++++++++++++++++------
 2 files changed, 18 insertions(+), 9 deletions(-)

[PATCH][v2 1/3] KVM: x86: Check LMA bit before set_efer

[Sheng Yang]

kvm_x86_ops->set_efer() would execute vcpu->arch.efer = efer, so the
checking of LMA bit didn't work.

Signed-off-by: Sheng Yang <sheng@linux.intel.com>
---
 arch/x86/kvm/x86.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index cd8a606..2cae460 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -715,11 +715,11 @@ static int set_efer(struct kvm_vcpu *vcpu, u64 efer)
 			return 1;
 	}
 
-	kvm_x86_ops->set_efer(vcpu, efer);
-
 	efer &= ~EFER_LMA;
 	efer |= vcpu->arch.efer & EFER_LMA;
 
+	kvm_x86_ops->set_efer(vcpu, efer);
+
 	vcpu->arch.efer = efer;
 
 	vcpu->arch.mmu.base_role.nxe = (efer & EFER_NX) && !tdp_enabled;
-- 
1.7.0.1

[PATCH][v2 2/3] KVM: Clean up duplicate assignment

[Sheng Yang]

mmu.free() already set root_hpa to INVALID_PAGE, no need to do it again in the
destory_kvm_mmu().

kvm_x86_ops->set_cr4() and set_efer() already assign cr4/efer to
vcpu->arch.cr4/efer, no need to do it again later.

Signed-off-by: Sheng Yang <sheng@linux.intel.com>
---
 arch/x86/kvm/mmu.c |    5 ++---
 arch/x86/kvm/x86.c |    4 +---
 2 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 95bee9d..5412185 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2450,10 +2450,9 @@ static int init_kvm_mmu(struct kvm_vcpu *vcpu)
 static void destroy_kvm_mmu(struct kvm_vcpu *vcpu)
 {
 	ASSERT(vcpu);
-	if (VALID_PAGE(vcpu->arch.mmu.root_hpa)) {
+	if (VALID_PAGE(vcpu->arch.mmu.root_hpa))
+		/* mmu.free() should set root_hpa = INVALID_PAGE */
 		vcpu->arch.mmu.free(vcpu);
-		vcpu->arch.mmu.root_hpa = INVALID_PAGE;
-	}
 }
 
 int kvm_mmu_reset_context(struct kvm_vcpu *vcpu)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 2cae460..764f89b 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -486,7 +486,7 @@ int __kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
 		return 1;
 
 	kvm_x86_ops->set_cr4(vcpu, cr4);
-	vcpu->arch.cr4 = cr4;
+
 	kvm_mmu_reset_context(vcpu);
 
 	return 0;
@@ -720,8 +720,6 @@ static int set_efer(struct kvm_vcpu *vcpu, u64 efer)
 
 	kvm_x86_ops->set_efer(vcpu, efer);
 
-	vcpu->arch.efer = efer;
-
 	vcpu->arch.mmu.base_role.nxe = (efer & EFER_NX) && !tdp_enabled;
 	kvm_mmu_reset_context(vcpu);
 
-- 
1.7.0.1

[PATCH][v2 3/3] VMX: x86: Only reset MMU when necessary

[Sheng Yang]

Only modifying some bits of CR0/CR4 needs paging mode switch.

Modify EFER.NXE bit would result in reserved bit updates.

Signed-off-by: Sheng Yang <sheng@linux.intel.com>
---
 arch/x86/kvm/x86.c |   16 ++++++++++++++--
 1 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 764f89b..f442da2 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -416,6 +416,10 @@ out:
 
 static int __kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
 {
+	unsigned long old_cr0 = kvm_read_cr0(vcpu);
+	unsigned long update_bits = X86_CR0_PG | X86_CR0_WP |
+				    X86_CR0_CD | X86_CR0_NW;
+
 	cr0 |= X86_CR0_ET;
 
 #ifdef CONFIG_X86_64
@@ -449,7 +453,8 @@ static int __kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
 
 	kvm_x86_ops->set_cr0(vcpu, cr0);
 
-	kvm_mmu_reset_context(vcpu);
+	if ((cr0 ^ old_cr0) & update_bits)
+		kvm_mmu_reset_context(vcpu);
 	return 0;
 }
 
@@ -487,7 +492,8 @@ int __kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
 
 	kvm_x86_ops->set_cr4(vcpu, cr4);
 
-	kvm_mmu_reset_context(vcpu);
+	if ((cr4 ^ old_cr4) & pdptr_bits)
+		kvm_mmu_reset_context(vcpu);
 
 	return 0;
 }
@@ -692,6 +698,8 @@ static u32 emulated_msrs[] = {
 
 static int set_efer(struct kvm_vcpu *vcpu, u64 efer)
 {
+	u64 old_efer = vcpu->arch.efer;
+
 	if (efer & efer_reserved_bits)
 		return 1;
 
@@ -723,6 +731,10 @@ static int set_efer(struct kvm_vcpu *vcpu, u64 efer)
 	vcpu->arch.mmu.base_role.nxe = (efer & EFER_NX) && !tdp_enabled;
 	kvm_mmu_reset_context(vcpu);
 
+	/* Update reserved bits */
+	if ((efer ^ old_efer) & EFER_NX)
+		kvm_mmu_reset_context(vcpu);
+
 	return 0;
 }
 
-- 
1.7.0.1

Re: [PATCH][v2 3/3] VMX: x86: Only reset MMU when necessary

[Avi Kivity]

On 05/12/2010 11:40 AM, Sheng Yang wrote:
> Only modifying some bits of CR0/CR4 needs paging mode switch.
>
> Modify EFER.NXE bit would result in reserved bit updates.
>
> Signed-off-by: Sheng Yang<sheng@linux.intel.com>
> ---
>   arch/x86/kvm/x86.c |   16 ++++++++++++++--
>   1 files changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 764f89b..f442da2 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -416,6 +416,10 @@ out:
>
>   static int __kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
>   {
> +	unsigned long old_cr0 = kvm_read_cr0(vcpu);
> +	unsigned long update_bits = X86_CR0_PG | X86_CR0_WP |
> +				    X86_CR0_CD | X86_CR0_NW;
> +
>    

CR0_WP...

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

Re: [PATCH][v2 3/3] VMX: x86: Only reset MMU when necessary

[Avi Kivity]

On 05/12/2010 11:54 AM, Sheng Yang wrote:
> On Wednesday 12 May 2010 16:47:36 you wrote:
>    
>> On 05/12/2010 11:40 AM, Sheng Yang wrote:
>>      
>>> Only modifying some bits of CR0/CR4 needs paging mode switch.
>>>
>>> Modify EFER.NXE bit would result in reserved bit updates.
>>>
>>> Signed-off-by: Sheng Yang<sheng@linux.intel.com>
>>> ---
>>>
>>>    arch/x86/kvm/x86.c |   16 ++++++++++++++--
>>>    1 files changed, 14 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>>> index 764f89b..f442da2 100644
>>> --- a/arch/x86/kvm/x86.c
>>> +++ b/arch/x86/kvm/x86.c
>>>
>>> @@ -416,6 +416,10 @@ out:
>>>    static int __kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
>>>    {
>>>
>>> +	unsigned long old_cr0 = kvm_read_cr0(vcpu);
>>> +	unsigned long update_bits = X86_CR0_PG | X86_CR0_WP |
>>> +				    X86_CR0_CD | X86_CR0_NW;
>>> +
>>>        
>> CR0_WP...
>>      
> ?
>
>    

Can't read, sorry.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

Re: [PATCH][v2 0/3] Some MMU related fix/clean up

[Marcelo Tosatti]

On Wed, May 12, 2010 at 04:40:39PM +0800, Sheng Yang wrote:
> Sheng Yang (3):
>   KVM: x86: Check LMA bit before set_efer
>   KVM: Clean up duplicate assignment
>   VMX: x86: Only reset MMU when necessary
> 
>  arch/x86/kvm/mmu.c |    5 ++---
>  arch/x86/kvm/x86.c |   22 ++++++++++++++++------
>  2 files changed, 18 insertions(+), 9 deletions(-)

Applied, thanks.