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Re: [Qemu-devel] QEMU ARM SMP: IPI delivery delayed until next main loop
From: |
Alex Züpke |
Subject: |
Re: [Qemu-devel] QEMU ARM SMP: IPI delivery delayed until next main loop event // how to improve IPI latency? |
Date: |
Mon, 15 Jun 2015 18:12:51 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 |
Am 15.06.2015 um 17:49 schrieb Peter Maydell:
> On 15 June 2015 at 16:36, Alex Züpke <address@hidden> wrote:
>> So this is the way to go:
>>
>> --- a/target-arm/translate.c
>> +++ b/target-arm/translate.c
>> @@ -4084,6 +4084,7 @@ static void gen_nop_hint(DisasContext *s, int val)
>> gen_set_pc_im(s, s->pc);
>> s->is_jmp = DISAS_WFI;
>> break;
>> + case 1: /* yield */
>> case 2: /* wfe */
>> gen_set_pc_im(s, s->pc);
>> s->is_jmp = DISAS_WFE;
>
> Actually I want to split out the yield code path from the wfe
> one, because some day we may actually implement WFE as WFE,
> at which point WFE has some trap-to-EL2 logic that YIELD
> doesn't. I was about to write a patch to do that...
OK.
Both the cpu_exit-after-sending-IPI or the YIELD patch would fix my issue, but
I think the YIELD one fits better.
I updated my testcase to YIELD during polling:
http://www.cs.hs-rm.de/~zuepke/qemu/ipi_yield.elf
3174 bytes, md5sum e74897e6b6d70f472db9e9d657780035
> (If you plan to run your custom OS under a hypervisor you
> might prefer SEV/WFE over YIELD, because then if your custom OS
> is under heavy load the hypervisor has a chance to swap this
> vcpu out and run some other one.)
>
> thanks
> -- PMM
>
Thanks for the hint!
Best regards
Alex
- Re: [Qemu-devel] QEMU ARM SMP: IPI delivery delayed until next main loop event // how to improve IPI latency?, (continued)
- Re: [Qemu-devel] QEMU ARM SMP: IPI delivery delayed until next main loop event // how to improve IPI latency?, Peter Maydell, 2015/06/16
- Re: [Qemu-devel] QEMU ARM SMP: IPI delivery delayed until next main loop event // how to improve IPI latency?, Alex Züpke, 2015/06/16
- Re: [Qemu-devel] QEMU ARM SMP: IPI delivery delayed until next main loop event // how to improve IPI latency?, Peter Maydell, 2015/06/16
- Re: [Qemu-devel] QEMU ARM SMP: IPI delivery delayed until next main loop event // how to improve IPI latency?, Alex Züpke, 2015/06/16
- Re: [Qemu-devel] QEMU ARM SMP: IPI delivery delayed until next main loop event // how to improve IPI latency?, Peter Maydell, 2015/06/19
Re: [Qemu-devel] QEMU ARM SMP: IPI delivery delayed until next main loop event // how to improve IPI latency?, Peter Maydell, 2015/06/15
Re: [Qemu-devel] QEMU ARM SMP: IPI delivery delayed until next main loop event // how to improve IPI latency?, Paolo Bonzini, 2015/06/19