linux-kernel - [PATCH 4/7] KVM: nVMX: move inject_page_fault tweak to .complete_mmu

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Date:   Wed, 17 Feb 2021 16:57:15 +0200
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     kvm@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Wanpeng Li <wanpengli@...cent.com>,
        Borislav Petkov <bp@...en8.de>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Joerg Roedel <joro@...tes.org>,
        Jim Mattson <jmattson@...gle.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Sean Christopherson <seanjc@...gle.com>,
        x86@...nel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)),
        Thomas Gleixner <tglx@...utronix.de>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        Maxim Levitsky <mlevitsk@...hat.com>
Subject: [PATCH 4/7] KVM: nVMX: move inject_page_fault tweak to .complete_mmu_init

This fixes a (mostly theoretical) bug which can happen if ept=0
on host and we run a nested guest which triggers a mmu context
reset while running nested.
In this case the .inject_page_fault callback will be lost.

Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>
---
 arch/x86/kvm/vmx/nested.c | 8 +-------
 arch/x86/kvm/vmx/nested.h | 1 +
 arch/x86/kvm/vmx/vmx.c    | 5 ++++-
 3 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 0b6dab6915a3..f9de729dbea6 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -419,7 +419,7 @@ static int nested_vmx_check_exception(struct kvm_vcpu *vcpu, unsigned long *exit
 }
 
 
-static void vmx_inject_page_fault_nested(struct kvm_vcpu *vcpu,
+void vmx_inject_page_fault_nested(struct kvm_vcpu *vcpu,
 		struct x86_exception *fault)
 {
 	struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
@@ -2620,9 +2620,6 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
 		vmcs_write64(GUEST_PDPTR3, vmcs12->guest_pdptr3);
 	}
 
-	if (!enable_ept)
-		vcpu->arch.walk_mmu->inject_page_fault = vmx_inject_page_fault_nested;
-
 	if ((vmcs12->vm_entry_controls & VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL) &&
 	    WARN_ON_ONCE(kvm_set_msr(vcpu, MSR_CORE_PERF_GLOBAL_CTRL,
 				     vmcs12->guest_ia32_perf_global_ctrl)))
@@ -4224,9 +4221,6 @@ static void load_vmcs12_host_state(struct kvm_vcpu *vcpu,
 	if (nested_vmx_load_cr3(vcpu, vmcs12->host_cr3, false, &ignored))
 		nested_vmx_abort(vcpu, VMX_ABORT_LOAD_HOST_PDPTE_FAIL);
 
-	if (!enable_ept)
-		vcpu->arch.walk_mmu->inject_page_fault = kvm_inject_page_fault;
-
 	nested_vmx_transition_tlb_flush(vcpu, vmcs12, false);
 
 	vmcs_write32(GUEST_SYSENTER_CS, vmcs12->host_ia32_sysenter_cs);
diff --git a/arch/x86/kvm/vmx/nested.h b/arch/x86/kvm/vmx/nested.h
index 197148d76b8f..2ab279744d38 100644
--- a/arch/x86/kvm/vmx/nested.h
+++ b/arch/x86/kvm/vmx/nested.h
@@ -36,6 +36,7 @@ void nested_vmx_pmu_entry_exit_ctls_update(struct kvm_vcpu *vcpu);
 void nested_mark_vmcs12_pages_dirty(struct kvm_vcpu *vcpu);
 bool nested_vmx_check_io_bitmaps(struct kvm_vcpu *vcpu, unsigned int port,
 				 int size);
+void vmx_inject_page_fault_nested(struct kvm_vcpu *vcpu,struct x86_exception *fault);
 
 static inline struct vmcs12 *get_vmcs12(struct kvm_vcpu *vcpu)
 {
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index bf6ef674d688..c43324df4877 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -3254,7 +3254,10 @@ static void vmx_load_mmu_pgd(struct kvm_vcpu *vcpu, unsigned long pgd,
 
 static void vmx_complete_mmu_init(struct kvm_vcpu *vcpu)
 {
-
+	if (!enable_ept && is_guest_mode(vcpu)) {
+		WARN_ON(mmu_is_nested(vcpu));
+		vcpu->arch.mmu->inject_page_fault = vmx_inject_page_fault_nested;
+	}
 }
 
 static bool vmx_is_valid_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
-- 
2.26.2