[PATCH V2 3/3] KVM/Hyper-V/VMX: Add direct tlb flush support

[lantianyu1986@gmail.com]

From: Vitaly Kuznetsov <vkuznets@redhat.com>

This patch is to enable Hyper-V direct tlb flush function
for vmx.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
---
 arch/x86/include/asm/hyperv-tlfs.h |  4 ++++
 arch/x86/kvm/vmx/evmcs.h           |  2 ++
 arch/x86/kvm/vmx/vmx.c             | 38 ++++++++++++++++++++++++++++++++++++++
 include/linux/kvm_host.h           |  1 +
 4 files changed, 45 insertions(+)

diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
index cf0b2a04271d..d53d6e4a6210 100644
--- a/arch/x86/include/asm/hyperv-tlfs.h
+++ b/arch/x86/include/asm/hyperv-tlfs.h
@@ -171,6 +171,7 @@
 #define HV_X64_ENLIGHTENED_VMCS_RECOMMENDED		BIT(14)
 
 /* Nested features. These are HYPERV_CPUID_NESTED_FEATURES.EAX bits. */
+#define HV_X64_NESTED_DIRECT_FLUSH			BIT(17)
 #define HV_X64_NESTED_GUEST_MAPPING_FLUSH		BIT(18)
 #define HV_X64_NESTED_MSR_BITMAP			BIT(19)
 
@@ -882,4 +883,7 @@ struct hv_tlb_flush_ex {
 	u64 gva_list[];
 } __packed;
 
+struct hv_partition_assist_pg {
+	u32 tlb_lock_count;
+};
 #endif
diff --git a/arch/x86/kvm/vmx/evmcs.h b/arch/x86/kvm/vmx/evmcs.h
index 39a24eec8884..07ebf6882a45 100644
--- a/arch/x86/kvm/vmx/evmcs.h
+++ b/arch/x86/kvm/vmx/evmcs.h
@@ -178,6 +178,8 @@ static inline void evmcs_load(u64 phys_addr)
 	struct hv_vp_assist_page *vp_ap =
 		hv_get_vp_assist_page(smp_processor_id());
 
+	if (current_evmcs->hv_enlightenments_control.nested_flush_hypercall)
+		vp_ap->nested_control.features.directhypercall = 1;
 	vp_ap->current_nested_vmcs = phys_addr;
 	vp_ap->enlighten_vmentry = 1;
 }
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 84f8d49a2fd2..a49be029864e 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -486,6 +486,34 @@ static int hv_remote_flush_tlb(struct kvm *kvm)
 	return hv_remote_flush_tlb_with_range(kvm, NULL);
 }
 
+static int hv_enable_direct_tlbflush(struct kvm_vcpu *vcpu)
+{
+	struct hv_enlightened_vmcs *evmcs;
+
+	/*
+	 * Synthetic VM-Exit is not enabled in current code and so All
+	 * evmcs in singe VM shares same assist page.
+	 */
+	if (!vcpu->kvm->hv_pa_pg) {
+		vcpu->kvm->hv_pa_pg = kzalloc(PAGE_SIZE, GFP_KERNEL);
+		if (!vcpu->kvm->hv_pa_pg)
+			return -ENOMEM;
+		pr_debug("KVM: Hyper-V: allocated PA_PG for %llx\n",
+		       (u64)&vcpu->kvm);
+	}
+
+	evmcs = (struct hv_enlightened_vmcs *)to_vmx(vcpu)->loaded_vmcs->vmcs;
+
+	evmcs->partition_assist_page =
+		__pa(vcpu->kvm->hv_pa_pg);
+	evmcs->hv_vm_id = (u64)vcpu->kvm;
+	evmcs->hv_enlightenments_control.nested_flush_hypercall = 1;
+
+	pr_debug("KVM: Hyper-V: enabled DIRECT flush for %llx\n",
+		 (u64)vcpu->kvm);
+	return 0;
+}
+
 #endif /* IS_ENABLED(CONFIG_HYPERV) */
 
 /*
@@ -6516,6 +6544,9 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu)
 		current_evmcs->hv_clean_fields |=
 			HV_VMX_ENLIGHTENED_CLEAN_FIELD_ALL;
 
+	if (static_branch_unlikely(&enable_evmcs))
+		current_evmcs->hv_vp_id = vcpu->arch.hyperv.vp_index;
+
 	/* MSR_IA32_DEBUGCTLMSR is zeroed on vmexit. Restore it if needed */
 	if (vmx->host_debugctlmsr)
 		update_debugctlmsr(vmx->host_debugctlmsr);
@@ -6583,6 +6614,7 @@ static struct kvm *vmx_vm_alloc(void)
 
 static void vmx_vm_free(struct kvm *kvm)
 {
+	kfree(kvm->hv_pa_pg);
 	vfree(to_kvm_vmx(kvm));
 }
 
@@ -7815,6 +7847,7 @@ static void vmx_exit(void)
 			if (!vp_ap)
 				continue;
 
+			vp_ap->nested_control.features.directhypercall = 0;
 			vp_ap->current_nested_vmcs = 0;
 			vp_ap->enlighten_vmentry = 0;
 		}
@@ -7854,6 +7887,11 @@ static int __init vmx_init(void)
 			pr_info("KVM: vmx: using Hyper-V Enlightened VMCS\n");
 			static_branch_enable(&enable_evmcs);
 		}
+
+		if (ms_hyperv.nested_features & HV_X64_NESTED_DIRECT_FLUSH)
+			vmx_x86_ops.enable_direct_tlbflush
+				= hv_enable_direct_tlbflush;
+
 	} else {
 		enlightened_vmcs = false;
 	}
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index c5da875f19e3..479ad76661e6 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -500,6 +500,7 @@ struct kvm {
 	struct srcu_struct srcu;
 	struct srcu_struct irq_srcu;
 	pid_t userspace_pid;
+	struct hv_partition_assist_pg *hv_pa_pg;
 };
 
 #define kvm_err(fmt, ...) \
-- 
2.14.5