Commit 4f0dcb54 authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

KVM: VMX: Remove direct write to vcpu->arch.cr0 during vCPU RESET/INIT 



Remove a bogus write to vcpu->arch.cr0 that immediately precedes
vmx_set_cr0() during vCPU RESET/INIT.  For RESET, this is a nop since
the "old" CR0 value is meaningless.  But for INIT, if the vCPU is coming
from paging enabled mode, crushing vcpu->arch.cr0 will cause the various
is_paging() checks in vmx_set_cr0() to get false negatives.

For the exit_lmode() case, the false negative is benign as vmx_set_efer()
is called immediately after vmx_set_cr0().

For EPT without unrestricted guest, the false negative will cause KVM to
unnecessarily run with CR3 load/store exiting.  But again, this is
benign, albeit sub-optimal.

Reviewed-by: default avatarReiji Watanabe <reijiw@google.com>
Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Message-Id: <20210713163324.627647-23-seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent ee5a5584

arch/x86/kvm/vmx/vmx.c

+1 −4
Original line number Diff line number Diff line
@@ -4387,7 +4387,6 @@ static void init_vmcs(struct vcpu_vmx *vmx) 
static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)

{

	struct vcpu_vmx *vmx = to_vmx(vcpu);

	u64 cr0;



	vmx->rmode.vm86_active = 0;

	vmx->spec_ctrl = 0;
@@ -4455,9 +4454,7 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event) 


	kvm_make_request(KVM_REQ_APIC_PAGE_RELOAD, vcpu);



	cr0 = X86_CR0_NW | X86_CR0_CD | X86_CR0_ET;

	vmx->vcpu.arch.cr0 = cr0;

	vmx_set_cr0(vcpu, cr0); /* enter rmode */

	vmx_set_cr0(vcpu, X86_CR0_NW | X86_CR0_CD | X86_CR0_ET);

	vmx_set_cr4(vcpu, 0);

	vmx_set_efer(vcpu, 0);