From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=49028 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1PkzyI-0002DS-0A for qemu-devel@nongnu.org; Thu, 03 Feb 2011 09:15:43 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1PkzyG-00019y-MT for qemu-devel@nongnu.org; Thu, 03 Feb 2011 09:15:41 -0500 Received: from mx1.redhat.com ([209.132.183.28]:29997) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1PkzyG-00019h-FO for qemu-devel@nongnu.org; Thu, 03 Feb 2011 09:15:40 -0500 Date: Thu, 3 Feb 2011 16:15:37 +0200 From: Gleb Natapov Subject: Re: [Qemu-devel] KVM: Windows 64-bit troubles with user space irqchip Message-ID: <20110203141537.GY14984@redhat.com> References: <4D496D77.2010405@siemens.com> <4D496FA6.8070301@siemens.com> <4D49738D.7080404@redhat.com> <4D4979BD.6080900@siemens.com> <20110202154611.GR14984@redhat.com> <4D497DAB.7010901@siemens.com> <4D4A64F2.8010309@redhat.com> <4D4A7629.1010506@siemens.com> <20110203100407.GA2449@amt.cnet> <4D4A7F4B.6050406@siemens.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4D4A7F4B.6050406@siemens.com> List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jan Kiszka Cc: Marcelo Tosatti , Avi Kivity , kvm , qemu-devel On Thu, Feb 03, 2011 at 11:11:23AM +0100, Jan Kiszka wrote: > On 2011-02-03 11:04, Marcelo Tosatti wrote: > > On Thu, Feb 03, 2011 at 10:32:25AM +0100, Jan Kiszka wrote: > >> On 2011-02-03 09:18, Avi Kivity wrote: > >>> On 02/02/2011 05:52 PM, Jan Kiszka wrote: > >>>>>> > >>>>> If there is no problem in the logic of this commit (and I do not see > >>>>> one yet) then we somewhere miss kicking vcpu when interrupt, that should be > >>>>> handled, arrives? > >>>> > >>>> I'm not yet confident about the logic of the kernel patch: mov to cr8 is > >>>> serializing. If the guest raises the tpr and then signals this with a > >>>> succeeding, non vm-exiting instruction to the other vcpus, one of those > >>>> could inject an interrupt with a higher priority than the previous tpr, > >>>> but a lower one than current tpr. QEMU user space would accept this > >>>> interrupt - and would likely surprise the guest. Do I miss something? > >>> > >>> apic_get_interrupt() is only called from the vcpu thread, so it should > >>> see a correct tpr. > >>> > >>> The only difference I can see with the patch is that we may issue a > >>> spurious cpu_interrupt(). But that shouldn't do anything bad, should it? > >> > >> I tested this yesterday, and it doesn't confuse Windows. It actually > >> receives quite a few spurious IRQs in normal operation, w/ or w/o the > >> kernel's tpr optimization. > > > > http://www.mail-archive.com/kvm@vger.kernel.org/msg41681.html > > Don't get the scenario yet: We do not inject (or set isr) over the > context of apic_set_irq caller. > > > > > tpr of a vcpu should always be inspected in vcpu context, instead of > > iothread context? > > Maybe this is true for the in-kernel model, but I don't see the issue > (anymore) for the way user space works. > With patch below I can boot Windows7. diff --git a/hw/apic.c b/hw/apic.c index 146deca..fdcac88 100644 --- a/hw/apic.c +++ b/hw/apic.c @@ -600,7 +600,7 @@ int apic_get_interrupt(DeviceState *d) intno = get_highest_priority_int(s->irr); if (intno < 0) return -1; - if (s->tpr && intno <= s->tpr) + if ((s->tpr >> 4) && (intno >> 4) <= (s->tpr >> 4)) return s->spurious_vec & 0xff; reset_bit(s->irr, intno); set_bit(s->isr, intno); -- Gleb.