linux-kernel - [PATCH v2 14/31] KVM: x86: hyper-v: Introduce fast kvm_hv_direct_tlb_flush

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Date:   Thu,  7 Apr 2022 17:56:28 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Michael Kelley <mikelley@...rosoft.com>,
        Siddharth Chandrasekaran <sidcha@...zon.de>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 14/31] KVM: x86: hyper-v: Introduce fast kvm_hv_direct_tlb_flush_exposed() check

Introduce a helper to quickly check if KVM needs to handle VMCALL/VMMCALL
from L2 in L0 to process Direct TLB flush requests.

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 arch/x86/include/asm/kvm_host.h | 1 +
 arch/x86/kvm/hyperv.c           | 6 ++++++
 arch/x86/kvm/hyperv.h           | 7 +++++++
 3 files changed, 14 insertions(+)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 7c607307a5d4..3be54b51d6bc 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -615,6 +615,7 @@ struct kvm_vcpu_hv {
 		u32 enlightenments_eax; /* HYPERV_CPUID_ENLIGHTMENT_INFO.EAX */
 		u32 enlightenments_ebx; /* HYPERV_CPUID_ENLIGHTMENT_INFO.EBX */
 		u32 syndbg_cap_eax; /* HYPERV_CPUID_SYNDBG_PLATFORM_CAPABILITIES.EAX */
+		u32 nested_features_eax; /* HYPERV_CPUID_NESTED_FEATURES.EAX */
 	} cpuid_cache;
 
 	/* Two rings for regular Hyper-V TLB flush and Direct TLB flush */
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 2b12f1b5c992..f08cf295d750 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -2256,6 +2256,12 @@ void kvm_hv_set_cpuid(struct kvm_vcpu *vcpu)
 		hv_vcpu->cpuid_cache.syndbg_cap_eax = entry->eax;
 	else
 		hv_vcpu->cpuid_cache.syndbg_cap_eax = 0;
+
+	entry = kvm_find_cpuid_entry(vcpu, HYPERV_CPUID_NESTED_FEATURES, 0);
+	if (entry)
+		hv_vcpu->cpuid_cache.nested_features_eax = entry->eax;
+	else
+		hv_vcpu->cpuid_cache.nested_features_eax = 0;
 }
 
 int kvm_hv_set_enforce_cpuid(struct kvm_vcpu *vcpu, bool enforce)
diff --git a/arch/x86/kvm/hyperv.h b/arch/x86/kvm/hyperv.h
index 3687e1e61e0d..c4f8064da606 100644
--- a/arch/x86/kvm/hyperv.h
+++ b/arch/x86/kvm/hyperv.h
@@ -169,6 +169,13 @@ static inline void kvm_hv_vcpu_empty_flush_tlb(struct kvm_vcpu *vcpu)
 	tlb_flush_ring->read_idx = tlb_flush_ring->write_idx;
 }
 
+static inline bool kvm_hv_direct_tlb_flush_exposed(struct kvm_vcpu *vcpu)
+{
+	struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
+
+	return hv_vcpu && (hv_vcpu->cpuid_cache.nested_features_eax & HV_X64_NESTED_DIRECT_FLUSH);
+}
+
 static inline bool kvm_hv_is_tlb_flush_hcall(struct kvm_vcpu *vcpu)
 {
 	struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
-- 
2.35.1