On 2017年08月16日 21:26, Radim Krčmář wrote: > 2017-08-15 21:58-0400, Lan Tianyu: >> These CR3 VMEXITs was introduced for platform without "unrestricted guest" >> support. This is to set ept identity table to guest CR3 in guest real >> mode because these platforms don't support ept real mode(CR0.PE and CR0.PG >> must be set to 1). But these VMEXITs is redundant for platforms with >> "unrestricted guest" support. >> >> Signed-off-by: Lan Tianyu <tianyu.lan@xxxxxxxxx> >> --- >> arch/x86/kvm/vmx.c | 22 +++++++++++++--------- >> 1 file changed, 13 insertions(+), 9 deletions(-) >> >> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c >> @@ -4311,7 +4313,9 @@ static void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3) >> } >> >> vmx_flush_tlb(vcpu); >> - vmcs_writel(GUEST_CR3, guest_cr3); >> + >> + if (!enable_unrestricted_guest || !enable_ept) >> + vmcs_writel(GUEST_CR3, guest_cr3); > > This looks wrong -- it would prevent update GUEST_CR3 outside of > non-root mode with enable_unrestricted_guest. > OK. Do you mean nest mode? I didn't consider that case. I thought there were three cases here. 1) Shadow page mode(enable_ept=0) 2) ept mode without unrestricted guest mode (ept=1, enable_unrestricted_guest = 0) 3) ept mode with unrestricted guest mode (ept=1, enable_unrestricted_guest = 1) >From my understanding, only (1) and (2) need to update guest cr3. If nest mode is still needed to update guest CR3, we can add is_guest_mode() in the if condition. Other choice is to just ignore setting guest cr3 for case3. The condition maybe changed to if (!(enable_unrestricted_guest && enable_ept)) vmcs_writel(GUEST_CR3, guest_cr3); -- Best regards Tianyu Lan
