linux-kernel - [PATCH] KVM: x86: take as_id into account when checking PGD

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Date:   Wed,  8 Jul 2020 16:00:23 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>, linux-kernel@...r.kernel.org
Subject: [PATCH] KVM: x86: take as_id into account when checking PGD

OVMF booted guest running on shadow pages crashes on TRIPLE FAULT after
enabling paging from SMM. The crash is triggered from mmu_check_root() and
is caused by kvm_is_visible_gfn() searching through memslots with as_id = 0
while vCPU may be in a different context (address space).

Introduce kvm_vcpu_is_visible_gfn() and use it from mmu_check_root().

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 arch/x86/kvm/mmu/mmu.c   | 2 +-
 include/linux/kvm_host.h | 1 +
 virt/kvm/kvm_main.c      | 8 ++++++++
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 4fd4b5de8996..309024210a35 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3668,7 +3668,7 @@ static int mmu_check_root(struct kvm_vcpu *vcpu, gfn_t root_gfn)
 {
 	int ret = 0;
 
-	if (!kvm_is_visible_gfn(vcpu->kvm, root_gfn)) {
+	if (!kvm_vcpu_is_visible_gfn(vcpu, root_gfn)) {
 		kvm_make_request(KVM_REQ_TRIPLE_FAULT, vcpu);
 		ret = 1;
 	}
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index d564855243d8..f74d2a5afc26 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -774,6 +774,7 @@ int kvm_clear_guest_page(struct kvm *kvm, gfn_t gfn, int offset, int len);
 int kvm_clear_guest(struct kvm *kvm, gpa_t gpa, unsigned long len);
 struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn);
 bool kvm_is_visible_gfn(struct kvm *kvm, gfn_t gfn);
+bool kvm_vcpu_is_visible_gfn(struct kvm_vcpu *vcpu, gfn_t gfn);
 unsigned long kvm_host_page_size(struct kvm_vcpu *vcpu, gfn_t gfn);
 void mark_page_dirty(struct kvm *kvm, gfn_t gfn);
 
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index a852af5c3214..b131c7da1d12 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1626,6 +1626,14 @@ bool kvm_is_visible_gfn(struct kvm *kvm, gfn_t gfn)
 }
 EXPORT_SYMBOL_GPL(kvm_is_visible_gfn);
 
+bool kvm_vcpu_is_visible_gfn(struct kvm_vcpu *vcpu, gfn_t gfn)
+{
+	struct kvm_memory_slot *memslot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);
+
+	return kvm_is_visible_memslot(memslot);
+}
+EXPORT_SYMBOL_GPL(kvm_vcpu_is_visible_gfn);
+
 unsigned long kvm_host_page_size(struct kvm_vcpu *vcpu, gfn_t gfn)
 {
 	struct vm_area_struct *vma;
-- 
2.25.4