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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: |
Sun, 04 Sep 2011 14:37:17 +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 2011-09-04 14:17, Avi Kivity wrote:
> On 08/31/2011 01:53 PM, Jan Kiszka wrote:
>> On 2011-08-31 10:25, Peter Maydell wrote:
>> > On 30 August 2011 20:28, Jan Kiszka<address@hidden> wrote:
>> >> 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.
>> >
>> > Can you elaborate a bit more on this? I don't think anybody has
>> > proposed links with their own internal state before in the qdev/qom
>> > discussions...
>>
>> That basic idea is to allow
>>
>> a) a discovery of the currently active IRQ path from source to sink
>> (that would be possible via QOM just using forward links)
>>
>> b) skip updating the states of IRQ routers in the common case, just
>> signaling directly the sink from the source (to allow in-kernel IRQ
>> delivery or to skip taking some device locks). Whenever some router
>> is queried for its current IRQ line state, it would have to ask the
>> preceding IRQ source for its state. So we need a backward link.
>>
>> We haven't thought about how this could be implemented in details yet
>> though. Among other things, it heavily depends on the final QOM design.
>>
>
> Looks like a similar path to the memory API. A declarative description
> of the interrupt hierarchy allows routes to be precalculated and flattened.
>
> (here it's strictly an optimization; with the memory API it's a
> requirement since kvm requires a flattened representation, and tcg is
> greatly simplified by it).
With current kvm device assignment it's mandatory as it only support
kernel/kernel IRQ delivery. Only vfio's eventfds will make it optional
(but still highly desirable).
Jan
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- Re: [Qemu-devel] [PATCH] pc: Clean up PIC-to-APIC IRQ path, (continued)
- Re: [Qemu-devel] [PATCH] pc: Clean up PIC-to-APIC IRQ path, Blue Swirl, 2011/09/04
- Re: [Qemu-devel] [PATCH] pc: Clean up PIC-to-APIC IRQ path, Edgar E. Iglesias, 2011/09/05
- Re: [Qemu-devel] [PATCH] pc: Clean up PIC-to-APIC IRQ path, Avi Kivity, 2011/09/04
- Re: [Qemu-devel] [PATCH] pc: Clean up PIC-to-APIC IRQ path, Anthony Liguori, 2011/09/04
- Re: [Qemu-devel] [PATCH] pc: Clean up PIC-to-APIC IRQ path, Avi Kivity, 2011/09/04
- Re: [Qemu-devel] [PATCH] pc: Clean up PIC-to-APIC IRQ path, Anthony Liguori, 2011/09/04
- Re: [Qemu-devel] [PATCH] pc: Clean up PIC-to-APIC IRQ path, Avi Kivity, 2011/09/04
- Re: [Qemu-devel] [PATCH] pc: Clean up PIC-to-APIC IRQ path, Blue Swirl, 2011/09/04
Re: [Qemu-devel] [PATCH] pc: Clean up PIC-to-APIC IRQ path, Blue Swirl, 2011/09/04
Re: [Qemu-devel] [PATCH] pc: Clean up PIC-to-APIC IRQ path, Avi Kivity, 2011/09/04
- 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, Anthony Liguori, 2011/09/04
Re: [Qemu-devel] [PATCH] pc: Clean up PIC-to-APIC IRQ path, Gleb Natapov, 2011/09/04