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Re: [Qemu-devel] KVM: Windows 64-bit troubles with user space irqchip
From: |
Jan Kiszka |
Subject: |
Re: [Qemu-devel] KVM: Windows 64-bit troubles with user space irqchip |
Date: |
Thu, 03 Feb 2011 15:27:51 +0100 |
User-agent: |
Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666 |
On 2011-02-03 15:15, Gleb Natapov wrote:
> 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/address@hidden/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.
Cool, /me too. I would just suggest
diff --git a/hw/apic.c b/hw/apic.c
index 05a115f..13bd7b4 100644
--- a/hw/apic.c
+++ b/hw/apic.c
@@ -582,6 +582,7 @@ int apic_get_interrupt(DeviceState *d)
{
APICState *s = DO_UPCAST(APICState, busdev.qdev, d);
int intno;
+ int tpr;
/* if the APIC is installed or enabled, we let the 8259 handle the
IRQs */
@@ -594,8 +595,10 @@ int apic_get_interrupt(DeviceState *d)
intno = get_highest_priority_int(s->irr);
if (intno < 0)
return -1;
- if (s->tpr && intno <= s->tpr)
+ tpr = s->tpr >> 4;
+ if (tpr && (intno >> 4) <= tpr) {
return s->spurious_vec & 0xff;
+ }
reset_bit(s->irr, intno);
set_bit(s->isr, intno);
apic_update_irq(s);
Unfortunately, that issue was not related to the emulation mode
problems of QEMU.
Thanks!
Jan
--
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux
- Re: [Qemu-devel] KVM: Windows 64-bit troubles with user space irqchip, (continued)
- Re: [Qemu-devel] KVM: Windows 64-bit troubles with user space irqchip, Avi Kivity, 2011/02/03
- Re: [Qemu-devel] KVM: Windows 64-bit troubles with user space irqchip, Jan Kiszka, 2011/02/03
- Re: [Qemu-devel] KVM: Windows 64-bit troubles with user space irqchip, Avi Kivity, 2011/02/03
- Re: [Qemu-devel] KVM: Windows 64-bit troubles with user space irqchip, Jan Kiszka, 2011/02/03
- Re: [Qemu-devel] KVM: Windows 64-bit troubles with user space irqchip, Marcelo Tosatti, 2011/02/03
- Re: [Qemu-devel] KVM: Windows 64-bit troubles with user space irqchip, Jan Kiszka, 2011/02/03
- Re: [Qemu-devel] KVM: Windows 64-bit troubles with user space irqchip, Gleb Natapov, 2011/02/03
- Re: [Qemu-devel] KVM: Windows 64-bit troubles with user space irqchip,
Jan Kiszka <=
- Re: [Qemu-devel] KVM: Windows 64-bit troubles with user space irqchip, Avi Kivity, 2011/02/06
- Re: [Qemu-devel] KVM: Windows 64-bit troubles with user space irqchip, Gleb Natapov, 2011/02/06