[PATCH v2 7/7] KVM: SVM: hyper-v: Direct Virtual Flush support

Vineeth Pillai
2021-04-15T13:44:27Z

From Hyper-V TLFS:
"The hypervisor exposes hypercalls (HvFlushVirtualAddressSpace,
HvFlushVirtualAddressSpaceEx, HvFlushVirtualAddressList, and
HvFlushVirtualAddressListEx) that allow operating systems to more
efficiently manage the virtual TLB. The L1 hypervisor can choose to
allow its guest to use those hypercalls and delegate the responsibility
to handle them to the L0 hypervisor. This requires the use of a
partition assist page."

Add the Direct Virtual Flush support for SVM.

Related VMX changes:
commit 6f6a657c9998 ("KVM/Hyper-V/VMX: Add direct tlb flush support")

Signed-off-by: Vineeth Pillai <viremana@linux.microsoft.com>
---
arch/x86/kvm/svm/svm.c | 48 ++++++++++++++++++++++++++++++++++++++++++
1 file changed, 48 insertions(+)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index f59f03b5c722..cff01256c47e 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -443,6 +443,32 @@ static void svm_init_osvw(struct kvm_vcpu *vcpu)
vcpu->arch.osvw.status |= 1;
}

+#if IS_ENABLED(CONFIG_HYPERV)
+static int hv_enable_direct_tlbflush(struct kvm_vcpu *vcpu)
+{
+ struct hv_enlightenments *hve;
+ struct hv_partition_assist_pg **p_hv_pa_pg =
+ &to_kvm_hv(vcpu->kvm)->hv_pa_pg;
+
+ if (!*p_hv_pa_pg)
+ *p_hv_pa_pg = kzalloc(PAGE_SIZE, GFP_KERNEL);
+
+ if (!*p_hv_pa_pg)
+ return -ENOMEM;
+
+ hve = (struct hv_enlightenments *)&to_svm(vcpu)->vmcb->hv_enlightenments;
+
+ hve->partition_assist_page = __pa(*p_hv_pa_pg);
+ hve->hv_vm_id = (unsigned long)vcpu->kvm;
+ if (!hve->hv_enlightenments_control.nested_flush_hypercall) {
+ hve->hv_enlightenments_control.nested_flush_hypercall = 1;
+ vmcb_mark_dirty(to_svm(vcpu)->vmcb, VMCB_HV_NESTED_ENLIGHTENMENTS);
+ }
+
+ return 0;
+}
+#endif
+
static int has_svm(void)
{
const char *msg;
@@ -1037,6 +1063,21 @@ static __init int svm_hardware_setup(void)
svm_x86_ops.tlb_remote_flush_with_range =
kvm_hv_remote_flush_tlb_with_range;
}
+
+ if (ms_hyperv.nested_features & HV_X64_NESTED_DIRECT_FLUSH) {
+ pr_info("kvm: Hyper-V Direct TLB Flush enabled\n");
+ for_each_online_cpu(cpu) {
+ struct hv_vp_assist_page *vp_ap =
+ hv_get_vp_assist_page(cpu);
+
+ if (!vp_ap)
+ continue;
+
+ vp_ap->nested_control.features.directhypercall = 1;
+ }
+ svm_x86_ops.enable_direct_tlbflush =
+ hv_enable_direct_tlbflush;
+ }
#endif

if (nrips) {
@@ -3921,6 +3962,13 @@ static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu)
}
svm->vmcb->save.cr2 = vcpu->arch.cr2;

+#if IS_ENABLED(CONFIG_HYPERV)
+ if (svm->vmcb->hv_enlightenments.hv_vp_id != to_hv_vcpu(vcpu)->vp_index) {
+ svm->vmcb->hv_enlightenments.hv_vp_id = to_hv_vcpu(vcpu)->vp_index;
+ vmcb_mark_dirty(svm->vmcb, VMCB_HV_NESTED_ENLIGHTENMENTS);
+ }
+#endif
+
/*
* Run with all-zero DR6 unless needed, so that we can get the exact cause
* of a #DB.
--
2.25.1