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[6/7] KVM: SVM: hyper-v: Enlightened MSR-Bitmap support

Message ID 5cf935068a9539146e033276b6d9a6c9b1e42119.1617804573.git.viremana@linux.microsoft.com (mailing list archive)
State New
Headers show
Series Hyper-V nested virt enlightenments for SVM | expand

Commit Message

Vineeth Pillai April 7, 2021, 2:41 p.m. UTC
Enlightened MSR-Bitmap as per TLFS:

 "The L1 hypervisor may collaborate with the L0 hypervisor to make MSR
  accesses more efficient. It can enable enlightened MSR bitmaps by setting
  the corresponding field in the enlightened VMCS to 1. When enabled, L0
  hypervisor does not monitor the MSR bitmaps for changes. Instead, the L1
  hypervisor must invalidate the corresponding clean field after making
  changes to one of the MSR bitmaps."

Enable this for SVM.

Related VMX changes:
commit ceef7d10dfb6 ("KVM: x86: VMX: hyper-v: Enlightened MSR-Bitmap support")

Signed-off-by: Vineeth Pillai <viremana@linux.microsoft.com>
---
 arch/x86/kvm/svm/svm.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

Comments

Vitaly Kuznetsov April 8, 2021, 11:22 a.m. UTC | #1
Vineeth Pillai <viremana@linux.microsoft.com> writes:

> Enlightened MSR-Bitmap as per TLFS:
>
>  "The L1 hypervisor may collaborate with the L0 hypervisor to make MSR
>   accesses more efficient. It can enable enlightened MSR bitmaps by setting
>   the corresponding field in the enlightened VMCS to 1. When enabled, L0
>   hypervisor does not monitor the MSR bitmaps for changes. Instead, the L1
>   hypervisor must invalidate the corresponding clean field after making
>   changes to one of the MSR bitmaps."
>
> Enable this for SVM.
>
> Related VMX changes:
> commit ceef7d10dfb6 ("KVM: x86: VMX: hyper-v: Enlightened MSR-Bitmap support")
>
> Signed-off-by: Vineeth Pillai <viremana@linux.microsoft.com>
> ---
>  arch/x86/kvm/svm/svm.c | 27 +++++++++++++++++++++++++++
>  1 file changed, 27 insertions(+)
>
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 6287cab61f15..3562a247b7e8 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -646,6 +646,27 @@ static bool msr_write_intercepted(struct kvm_vcpu *vcpu, u32 msr)
>  	return !!test_bit(bit_write,  &tmp);
>  }
>  
> +#if IS_ENABLED(CONFIG_HYPERV)
> +static inline void hv_vmcb_dirty_nested_enlightenments(struct kvm_vcpu *vcpu)
> +{
> +	struct vmcb *vmcb = to_svm(vcpu)->vmcb;
> +
> +	/*
> +	 * vmcb can be NULL if called during early vcpu init.
> +	 * And its okay not to mark vmcb dirty during vcpu init
> +	 * as we mark it dirty unconditionally towards end of vcpu
> +	 * init phase.
> +	 */
> +	if (vmcb && vmcb_is_clean(vmcb, VMCB_HV_NESTED_ENLIGHTENMENTS) &&
> +	    vmcb->hv_enlightenments.hv_enlightenments_control.msr_bitmap)
> +		vmcb_mark_dirty(vmcb, VMCB_HV_NESTED_ENLIGHTENMENTS);

vmcb_is_clean() check seems to be superfluous, vmcb_mark_dirty() does no
harm if the bit was already cleared.

> +}
> +#else
> +static inline void hv_vmcb_dirty_nested_enlightenments(struct kvm_vcpu *vcpu)
> +{
> +}
> +#endif
> +
>  static void set_msr_interception_bitmap(struct kvm_vcpu *vcpu, u32 *msrpm,
>  					u32 msr, int read, int write)
>  {
> @@ -677,6 +698,9 @@ static void set_msr_interception_bitmap(struct kvm_vcpu *vcpu, u32 *msrpm,
>  	write ? clear_bit(bit_write, &tmp) : set_bit(bit_write, &tmp);
>  
>  	msrpm[offset] = tmp;
> +
> +	hv_vmcb_dirty_nested_enlightenments(vcpu);
> +
>  }
>  
>  void set_msr_interception(struct kvm_vcpu *vcpu, u32 *msrpm, u32 msr,
> @@ -1135,6 +1159,9 @@ static void hv_init_vmcb(struct vmcb *vmcb)
>  	if (npt_enabled &&
>  	    ms_hyperv.nested_features & HV_X64_NESTED_ENLIGHTENED_TLB)
>  		hve->hv_enlightenments_control.enlightened_npt_tlb = 1;
> +
> +	if (ms_hyperv.nested_features & HV_X64_NESTED_MSR_BITMAP)
> +		hve->hv_enlightenments_control.msr_bitmap = 1;
>  }
>  #else
>  static inline void hv_init_vmcb(struct vmcb *vmcb)
Paolo Bonzini April 8, 2021, 3:47 p.m. UTC | #2
On 07/04/21 16:41, Vineeth Pillai wrote:
>   
> +#if IS_ENABLED(CONFIG_HYPERV)
> +static inline void hv_vmcb_dirty_nested_enlightenments(struct kvm_vcpu *vcpu)
> +{
> +	struct vmcb *vmcb = to_svm(vcpu)->vmcb;
> +
> +	/*
> +	 * vmcb can be NULL if called during early vcpu init.
> +	 * And its okay not to mark vmcb dirty during vcpu init
> +	 * as we mark it dirty unconditionally towards end of vcpu
> +	 * init phase.
> +	 */
> +	if (vmcb && vmcb_is_clean(vmcb, VMCB_HV_NESTED_ENLIGHTENMENTS) &&
> +	    vmcb->hv_enlightenments.hv_enlightenments_control.msr_bitmap)
> +		vmcb_mark_dirty(vmcb, VMCB_HV_NESTED_ENLIGHTENMENTS);
> +}

In addition to what Vitaly said, can svm->vmcb really be NULL?  If so it 
might be better to reorder initializations and skip the NULL check.

Paolo
diff mbox series

Patch

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 6287cab61f15..3562a247b7e8 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -646,6 +646,27 @@  static bool msr_write_intercepted(struct kvm_vcpu *vcpu, u32 msr)
 	return !!test_bit(bit_write,  &tmp);
 }
 
+#if IS_ENABLED(CONFIG_HYPERV)
+static inline void hv_vmcb_dirty_nested_enlightenments(struct kvm_vcpu *vcpu)
+{
+	struct vmcb *vmcb = to_svm(vcpu)->vmcb;
+
+	/*
+	 * vmcb can be NULL if called during early vcpu init.
+	 * And its okay not to mark vmcb dirty during vcpu init
+	 * as we mark it dirty unconditionally towards end of vcpu
+	 * init phase.
+	 */
+	if (vmcb && vmcb_is_clean(vmcb, VMCB_HV_NESTED_ENLIGHTENMENTS) &&
+	    vmcb->hv_enlightenments.hv_enlightenments_control.msr_bitmap)
+		vmcb_mark_dirty(vmcb, VMCB_HV_NESTED_ENLIGHTENMENTS);
+}
+#else
+static inline void hv_vmcb_dirty_nested_enlightenments(struct kvm_vcpu *vcpu)
+{
+}
+#endif
+
 static void set_msr_interception_bitmap(struct kvm_vcpu *vcpu, u32 *msrpm,
 					u32 msr, int read, int write)
 {
@@ -677,6 +698,9 @@  static void set_msr_interception_bitmap(struct kvm_vcpu *vcpu, u32 *msrpm,
 	write ? clear_bit(bit_write, &tmp) : set_bit(bit_write, &tmp);
 
 	msrpm[offset] = tmp;
+
+	hv_vmcb_dirty_nested_enlightenments(vcpu);
+
 }
 
 void set_msr_interception(struct kvm_vcpu *vcpu, u32 *msrpm, u32 msr,
@@ -1135,6 +1159,9 @@  static void hv_init_vmcb(struct vmcb *vmcb)
 	if (npt_enabled &&
 	    ms_hyperv.nested_features & HV_X64_NESTED_ENLIGHTENED_TLB)
 		hve->hv_enlightenments_control.enlightened_npt_tlb = 1;
+
+	if (ms_hyperv.nested_features & HV_X64_NESTED_MSR_BITMAP)
+		hve->hv_enlightenments_control.msr_bitmap = 1;
 }
 #else
 static inline void hv_init_vmcb(struct vmcb *vmcb)