From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gleb Natapov Subject: Re: [PATCH 13/15] Add NMI injection support to SVM. Date: Sun, 19 Apr 2009 16:24:34 +0300 Message-ID: <20090419132434.GH10126@redhat.com> References: <1239616545-25199-1-git-send-email-gleb@redhat.com> <1239616545-25199-14-git-send-email-gleb@redhat.com> <49E8DEC1.4030802@web.de> <20090419131735.GG10126@redhat.com> <49EB2559.4000704@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Jan Kiszka , kvm@vger.kernel.org, joerg.roedel@amd.com, sheng@linux.intel.com, Dmitry Baryshkov To: Avi Kivity Return-path: Received: from mx2.redhat.com ([66.187.237.31]:41895 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757708AbZDSNYj (ORCPT ); Sun, 19 Apr 2009 09:24:39 -0400 Content-Disposition: inline In-Reply-To: <49EB2559.4000704@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Sun, Apr 19, 2009 at 04:21:29PM +0300, Avi Kivity wrote: > Gleb Natapov wrote: >> On Fri, Apr 17, 2009 at 09:55:45PM +0200, Jan Kiszka wrote: >> >>> Gleb Natapov wrote: >>> >>>> Signed-off-by: Gleb Natapov >>>> --- >>>> arch/x86/include/asm/kvm_host.h | 1 + >>>> arch/x86/kvm/svm.c | 49 +++++++++++++++++++++++++++++++++++++- >>>> 2 files changed, 48 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h >>>> index 8b6f6e9..057a612 100644 >>>> --- a/arch/x86/include/asm/kvm_host.h >>>> +++ b/arch/x86/include/asm/kvm_host.h >>>> @@ -766,6 +766,7 @@ enum { >>>> #define HF_GIF_MASK (1 << 0) >>>> #define HF_HIF_MASK (1 << 1) >>>> #define HF_VINTR_MASK (1 << 2) >>>> +#define HF_NMI_MASK (1 << 3) >>>> /* >>>> * Hardware virtualization extension instructions may fault if a >>>> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c >>>> index c605477..cd60fd7 100644 >>>> --- a/arch/x86/kvm/svm.c >>>> +++ b/arch/x86/kvm/svm.c >>>> @@ -1834,6 +1834,13 @@ static int cpuid_interception(struct vcpu_svm *svm, struct kvm_run *kvm_run) >>>> return 1; >>>> } >>>> +static int iret_interception(struct vcpu_svm *svm, struct kvm_run >>>> *kvm_run) >>>> +{ >>>> + svm->vmcb->control.intercept &= ~(1UL << INTERCEPT_IRET); >>>> + svm->vcpu.arch.hflags &= ~HF_NMI_MASK; >>>> + return 0; >>>> +} >>>> >>> First, this must return 1 (or set an exit reason, but there is no reason >>> to escape to user space here). And second, I think a corner case is not >>> handled the same way as on real iron: If there is already the next NMI >>> waiting, we will inject it before iret, not after its execution as it >>> should be. >>> >>> No easy solution for this yet. Maybe emulating iret, but there is no >>> implementation, specifically for protected mode. Maybe setting a >>> breakpoint. Or maybe enforcing a single step exception. Nothing trivial >>> in this list. On the other hand, this may only be a slight imprecision >>> of the virtualization. Need to think about it. >>> >>> >> What about this: >> Instead of clearing HF_NMI_MASK in iret_interception() we can set >> another flag (HF_IRET) and on guest entry clear HF_NMI_MASK (and >> HF_IRET) if HF_IRET is set, but do that after checking for NMI >> injection. The pending NMI will be injected on the next entry. >> Also not how real HW works, but may be better then current situation. >> > > There may not be a next entry if the guest is in a tight loop. Given > NMIs are used for watchdogs, that's not good. > We don't exit a guest after kvm time slice ends? -- Gleb.