From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH] KVM: x86: fix eflags state following processor init/reset Date: Tue, 3 Nov 2015 11:47:15 +0100 Message-ID: <563890B3.2090704@redhat.com> References: <287435CB-DC24-4E59-9320-A8F75DAA5555@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: kvm list , Linux Kernel Mailing List To: Nadav Amit , Wanpeng Li Return-path: In-Reply-To: <287435CB-DC24-4E59-9320-A8F75DAA5555@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 28/10/2015 09:10, Nadav Amit wrote: > Here are my 5 cents. Note that vmx_vcpu_reset calls: >=20 > vmcs_writel(GUEST_RFLAGS, 0x02); >=20 > (And the RFLAGS value is not cached by KVM, so no consistency problem= should > occur.) >=20 > You may want to change the value into constant or call a wrapper func= tion > for setting RFLAGS, but I don=92t see something broken in the functio= nality. I agree. Wanpeng, if this is just a cleanup, can you send v2 that removes or modifies the existing call to vmcs_writel? If there is a bug, can you write a unit test for it? It should be possible to test for the problem using INIT+SIPI on an AP. Thanks, Paolo > Regards, > Nadav >=20 > Wanpeng Li wrote: >=20 >> Ping, :-) >> On 10/21/15 2:28 PM, Wanpeng Li wrote: >>> Reference SDM 3.4.3: >>> >>> Following initialization of the processor (either by asserting the >>> RESET pin or the INIT pin), the state of the EFLAGS register is >>> 00000002H. >>> >>> However, the eflags fixed bit is not set and other bits are also no= t >>> cleared during the init/reset in kvm. >>> >>> This patch fix it by set eflags register to 00000002H following >>> initialization of the processor. >>> >>> Signed-off-by: Wanpeng Li >>> --- >>> arch/x86/kvm/vmx.c | 1 + >>> 1 file changed, 1 insertion(+) >>> >>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c >>> index b680c2e..326f6ea 100644 >>> --- a/arch/x86/kvm/vmx.c >>> +++ b/arch/x86/kvm/vmx.c >>> @@ -4935,6 +4935,7 @@ static void vmx_vcpu_reset(struct kvm_vcpu *v= cpu, bool init_event) >>> vmx_set_efer(vcpu, 0); >>> vmx_fpu_activate(vcpu); >>> update_exception_bitmap(vcpu); >>> + vmx_set_rflags(vcpu, X86_EFLAGS_FIXED); >>> vpid_sync_context(vmx->vpid); >>> } >> >> -- >> To unsubscribe from this list: send the line "unsubscribe kvm" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html >=20 >=20