linux-kernel - [PATCH] KVM: VMX: Explicitly check for hv_remote_flush

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Message-Id: <20200924180429.10016-1-sean.j.christopherson@intel.com>
Date:   Thu, 24 Sep 2020 11:04:29 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] KVM: VMX: Explicitly check for hv_remote_flush_tlb when loading pgd()

Explicitly check that kvm_x86_ops.tlb_remote_flush() points at Hyper-V's
implementation for PV flushing instead of assuming that a non-NULL
implementation means running on Hyper-V.  Wrap the related logic in
ifdeffery as hv_remote_flush_tlb() is defined iff CONFIG_HYPERV!=n.

Short term, the explicit check makes it more obvious why a non-NULL
tlb_remote_flush() triggers EPTP shenanigans.  Long term, this will
allow TDX to define its own implementation of tlb_remote_flush() without
running afoul of Hyper-V.

Cc: Vitaly Kuznetsov <vkuznets@...hat.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
---
 arch/x86/kvm/vmx/vmx.c | 7 +++++--
 arch/x86/kvm/vmx/vmx.h | 2 ++
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 6f9a0c6d5dc5..a56fa9451b84 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -3073,14 +3073,15 @@ static void vmx_load_mmu_pgd(struct kvm_vcpu *vcpu, unsigned long pgd,
 		eptp = construct_eptp(vcpu, pgd, pgd_level);
 		vmcs_write64(EPT_POINTER, eptp);
 
-		if (kvm_x86_ops.tlb_remote_flush) {
+#if IS_ENABLED(CONFIG_HYPERV)
+		if (kvm_x86_ops.tlb_remote_flush == hv_remote_flush_tlb) {
 			spin_lock(&to_kvm_vmx(kvm)->ept_pointer_lock);
 			to_vmx(vcpu)->ept_pointer = eptp;
 			to_kvm_vmx(kvm)->ept_pointers_match
 				= EPT_POINTERS_CHECK;
 			spin_unlock(&to_kvm_vmx(kvm)->ept_pointer_lock);
 		}
-
+#endif
 		if (!enable_unrestricted_guest && !is_paging(vcpu))
 			guest_cr3 = to_kvm_vmx(kvm)->ept_identity_map_addr;
 		else if (test_bit(VCPU_EXREG_CR3, (ulong *)&vcpu->arch.regs_avail))
@@ -6956,7 +6957,9 @@ static int vmx_create_vcpu(struct kvm_vcpu *vcpu)
 
 static int vmx_vm_init(struct kvm *kvm)
 {
+#if IS_ENABLED(CONFIG_HYPERV)
 	spin_lock_init(&to_kvm_vmx(kvm)->ept_pointer_lock);
+#endif
 
 	if (!ple_gap)
 		kvm->arch.pause_in_guest = true;
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index d7ec66db5eb8..51107b7309bc 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -316,8 +316,10 @@ struct kvm_vmx {
 	bool ept_identity_pagetable_done;
 	gpa_t ept_identity_map_addr;
 
+#if IS_ENABLED(CONFIG_HYPERV)
 	enum ept_pointers_status ept_pointers_match;
 	spinlock_t ept_pointer_lock;
+#endif
 };
 
 bool nested_vmx_allowed(struct kvm_vcpu *vcpu);
-- 
2.28.0