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Re: [Qemu-devel] [PATCH] pc: Clean up PIC-to-APIC IRQ path
From: |
Jan Kiszka |
Subject: |
Re: [Qemu-devel] [PATCH] pc: Clean up PIC-to-APIC IRQ path |
Date: |
Tue, 30 Aug 2011 21:28:08 +0200 |
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 2011-08-30 21:19, Blue Swirl wrote:
> On Mon, Aug 29, 2011 at 9:13 PM, Avi Kivity <address@hidden> wrote:
>> On 08/30/2011 12:06 AM, Jan Kiszka wrote:
>>>
>>>>
>>>> Does this need to be save/restored for migration?
>>>
>>> Nope, but we need some other measure. I thought to remember the pic was
>>> refreshing this after load, but I do not find any traces of this now. We
>>> likely need a post_load handler in the i8259 that re-asserts the IRQ as
>>> required.
>>>
>>
>> We need some kind of two phase restore. In the first phase all state is
>> restored; since some of that state drivers outputs that are input to other
>> devices, they may experience an edge, and we need to supress that. In the
>> second phase edge detection is unsupressed and the device goes live.
>
> No. Devices may not perform any externally visible activities (like
> toggle a qemu_irq) during or after load because 1) qemu_irq is
> stateless and 2) since the receiving end is also freshly loaded, both
> states are already in synch without any calls or toggling.
Yes, that's the current state. Once we have bidirectional IRQ links in
place (pushing downward, querying upward - required to skip IRQ routers
for fast, lockless deliveries), that should change again.
For now, that's what I realized in the meantime as well, we can't help
saving pic_level in the APIC state.
What is the state of substates in pre-1.0? Do we try to use those again
in favor of simple field additions under a new state version?
Jan
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- [Qemu-devel] [PATCH] pc: Clean up PIC-to-APIC IRQ path, Jan Kiszka, 2011/08/27
- Re: [Qemu-devel] [PATCH] pc: Clean up PIC-to-APIC IRQ path, Blue Swirl, 2011/08/28
- Re: [Qemu-devel] [PATCH] pc: Clean up PIC-to-APIC IRQ path, Anthony Liguori, 2011/08/29
- Re: [Qemu-devel] [PATCH] pc: Clean up PIC-to-APIC IRQ path, Jan Kiszka, 2011/08/29
- Re: [Qemu-devel] [PATCH] pc: Clean up PIC-to-APIC IRQ path, Avi Kivity, 2011/08/29
- Re: [Qemu-devel] [PATCH] pc: Clean up PIC-to-APIC IRQ path, Jan Kiszka, 2011/08/29
- Re: [Qemu-devel] [PATCH] pc: Clean up PIC-to-APIC IRQ path, Blue Swirl, 2011/08/30
- Re: [Qemu-devel] [PATCH] pc: Clean up PIC-to-APIC IRQ path,
Jan Kiszka <=
- Re: [Qemu-devel] [PATCH] pc: Clean up PIC-to-APIC IRQ path, Blue Swirl, 2011/08/30
- Re: [Qemu-devel] [PATCH] pc: Clean up PIC-to-APIC IRQ path, Peter Maydell, 2011/08/31
- Re: [Qemu-devel] [PATCH] pc: Clean up PIC-to-APIC IRQ path, Jan Kiszka, 2011/08/31
- Re: [Qemu-devel] [PATCH] pc: Clean up PIC-to-APIC IRQ path, Blue Swirl, 2011/08/31
- Re: [Qemu-devel] [PATCH] pc: Clean up PIC-to-APIC IRQ path, Jan Kiszka, 2011/08/31
- Re: [Qemu-devel] [PATCH] pc: Clean up PIC-to-APIC IRQ path, Blue Swirl, 2011/08/31
- Re: [Qemu-devel] [PATCH] pc: Clean up PIC-to-APIC IRQ path, Avi Kivity, 2011/08/31
- Re: [Qemu-devel] [PATCH] pc: Clean up PIC-to-APIC IRQ path, Blue Swirl, 2011/08/31
- Re: [Qemu-devel] [PATCH] pc: Clean up PIC-to-APIC IRQ path, Edgar E. Iglesias, 2011/08/31
- Re: [Qemu-devel] [PATCH] pc: Clean up PIC-to-APIC IRQ path, Jan Kiszka, 2011/08/31