KVM: SVM: hyper-v: Direct Virtual Flush support

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 6f6a657c99 ("KVM/Hyper-V/VMX: Add direct tlb flush support")

Signed-off-by: Vineeth Pillai <viremana@linux.microsoft.com>
Message-Id: <fc8d24d8eb7017266bb961e39a171b0caf298d7f.1622730232.git.viremana@linux.microsoft.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/Makefile

@@ -32,6 +32,10 @@ kvm-intel-$(CONFIG_X86_SGX_KVM)	+= vmx/sgx.o
 
 kvm-amd-y		+= svm/svm.o svm/vmenter.o svm/pmu.o svm/nested.o svm/avic.o svm/sev.o
 
+ifdef CONFIG_HYPERV
+kvm-amd-y		+= svm/svm_onhyperv.o
+endif
+
 obj-$(CONFIG_KVM)	+= kvm.o
 obj-$(CONFIG_KVM_INTEL)	+= kvm-intel.o
 obj-$(CONFIG_KVM_AMD)	+= kvm-amd.o

arch/x86/kvm/svm/svm.c

@@ -3781,6 +3781,8 @@ static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu)
 	}
 	svm->vmcb->save.cr2 = vcpu->arch.cr2;
 
+	svm_hv_update_vp_id(svm->vmcb, vcpu);
+
 	/*
 	 * Run with all-zero DR6 unless needed, so that we can get the exact cause
 	 * of a #DB.

arch/x86/kvm/svm/svm_onhyperv.c

@@ -0,0 +1,41 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * KVM L1 hypervisor optimizations on Hyper-V for SVM.
+ */
+
+#include <linux/kvm_host.h>
+#include "kvm_cache_regs.h"
+
+#include <asm/mshyperv.h>
+
+#include "svm.h"
+#include "svm_ops.h"
+
+#include "hyperv.h"
+#include "kvm_onhyperv.h"
+#include "svm_onhyperv.h"
+
+int svm_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->control.reserved_sw;
+
+	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;
+}
+

arch/x86/kvm/svm/svm_onhyperv.h

@@ -36,6 +36,8 @@ struct hv_enlightenments {
  */
 #define VMCB_HV_NESTED_ENLIGHTENMENTS VMCB_SW
 
+int svm_hv_enable_direct_tlbflush(struct kvm_vcpu *vcpu);
+
 static inline void svm_hv_init_vmcb(struct vmcb *vmcb)
 {
 	struct hv_enlightenments *hve =
@@ -55,6 +57,23 @@ static inline void svm_hv_hardware_setup(void)
 		svm_x86_ops.tlb_remote_flush_with_range =
 				hv_remote_flush_tlb_with_range;
 	}
+
+	if (ms_hyperv.nested_features & HV_X64_NESTED_DIRECT_FLUSH) {
+		int cpu;
+
+		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 =
+				svm_hv_enable_direct_tlbflush;
+	}
 }
 
 static inline void svm_hv_vmcb_dirty_nested_enlightenments(
@@ -74,6 +93,19 @@ static inline void svm_hv_vmcb_dirty_nested_enlightenments(
 	    hve->hv_enlightenments_control.msr_bitmap)
 		vmcb_mark_dirty(vmcb, VMCB_HV_NESTED_ENLIGHTENMENTS);
 }
+
+static inline void svm_hv_update_vp_id(struct vmcb *vmcb,
+		struct kvm_vcpu *vcpu)
+{
+	struct hv_enlightenments *hve =
+		(struct hv_enlightenments *)vmcb->control.reserved_sw;
+	u32 vp_index = kvm_hv_get_vpindex(vcpu);
+
+	if (hve->hv_vp_id != vp_index) {
+		hve->hv_vp_id = vp_index;
+		vmcb_mark_dirty(vmcb, VMCB_HV_NESTED_ENLIGHTENMENTS);
+	}
+}
 #else
 
 static inline void svm_hv_init_vmcb(struct vmcb *vmcb)
@@ -88,6 +120,11 @@ static inline void svm_hv_vmcb_dirty_nested_enlightenments(
 		struct kvm_vcpu *vcpu)
 {
 }
+
+static inline void svm_hv_update_vp_id(struct vmcb *vmcb,
+		struct kvm_vcpu *vcpu)
+{
+}
 #endif /* CONFIG_HYPERV */
 
 #endif /* __ARCH_X86_KVM_SVM_ONHYPERV_H__ */