[PATCH v2 6/7] KVM: SVM: hyper-v: Enlightened MSR-Bitmap support

Vineeth Pillai
2021-04-15T13:44:25Z

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 de141d5ae5fb..f59f03b5c722 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -649,6 +649,27 @@ 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)
{
@@ -680,6 +701,9 @@ 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,
@@ -1143,6 +1167,9 @@ 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)
--
2.25.1