[PATCH v2 02/10] KVM: x86: Clear KVM's cached guest CR3 at RESET/INIT

[Sean Christopherson]

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@xxxxxxxxxxxxxxx
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
 arch/x86/kvm/x86.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index e77a5bf2d940..2cb38c67ed43 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10899,6 +10899,9 @@ 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
-- 
2.33.0.464.g1972c5931b-goog