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KVM: x86: Clear KVM's cached guest CR3 at RESET/INIT

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Explicitly zero the guest's CR3 and mark it available+dirty at RESET/INIT.
Per Intel's SDM and AMD's APM, CR3 is zeroed at both RESET and INIT.  For
RESET, this is a nop as vcpu is zero-allocated.  For INIT, the bug has
likely escaped notice because no firmware/kernel puts its page tables root
at PA=0, let alone relies on INIT to get the desired CR3 for such page
tables.

Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210921000303.400537-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2021-09-20 17:02:55 -07:00 committed by Paolo Bonzini
parent 7117003fe4
commit 03a6e84069
1 changed files with 3 additions and 0 deletions
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3
arch/x86/kvm/x86.c
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@ -10895,6 +10895,9 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
kvm_set_rflags(vcpu, X86_EFLAGS_FIXED);
kvm_rip_write(vcpu, 0xfff0);
vcpu->arch.cr3 = 0;
kvm_register_mark_dirty(vcpu, VCPU_EXREG_CR3);
/*
* CR0.CD/NW are set on RESET, preserved on INIT. Note, some versions
* of Intel's SDM list CD/NW as being set on INIT, but they contradict