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Re: [Qemu-devel] [PATCH v4 05/11] suspend: add infrastructure
From: |
Gerd Hoffmann |
Subject: |
Re: [Qemu-devel] [PATCH v4 05/11] suspend: add infrastructure |
Date: |
Tue, 14 Feb 2012 09:57:01 +0100 |
User-agent: |
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.26) Gecko/20120130 Red Hat/3.1.18-1.el6_2 Thunderbird/3.1.18 |
On 02/14/12 09:37, Gleb Natapov wrote:
> On Tue, Feb 14, 2012 at 09:18:34AM +0100, Gerd Hoffmann wrote:
>> Hi,
>>
>>> Shouldn't we stop the whole VM at some point, not only vcpu that
>>> does ACPI IO? May be I missed where it is done in the patch series.
>>
>> It isn't hidden elsewhere, qemu doesn't do it. The code was like that
>> before, and I think the reason is that the guest has to stop the other
>> cpus before entering s3.
>>
> Current code calls qemu_system_reset_request() which takes care of
> stopping (and reseting) all vcpus (and rest of the machine) by setting
> reset_requested flag immediately on suspend.
No. The current code simply has no separate suspend and wakeup steps.
> We cannot just stop
> current cpu on S3 and delay reset till wakeup since guest can leave
> other vcpus in spinning state and they will take 100% of host cpu while
> guest is suspended.
I see. I've expeced the the guest os putting them into a hlt loop or
some simliar idle state. Play save and expliticly pausing them all is
certainly good from a robustness perspective.
> I think it is also important to reset all device
> immediately to ensure that no device will do DMA into main memory after
> suspend.
Didn't investigate yet, but I suspect this could break wakeup from pci
devices (nic, usb-tablet via uhci) ...
> Technically if this happens it would be a guest bug since
> guest should make sure that devices are stopped before entering S3,
> but I wouldn't want to debug such bug report :)
... and it shouldn't be needed. Although I agree that bugs in that area
are nasty to debug ...
cheers,
Gerd
- [Qemu-devel] [PATCH v4 02/11] acpi: add ACPIREGS, (continued)
- [Qemu-devel] [PATCH v4 02/11] acpi: add ACPIREGS, Gerd Hoffmann, 2012/02/09
- [Qemu-devel] [PATCH v4 07/11] suspend: add system_wakeup monitor command, Gerd Hoffmann, 2012/02/09
- [Qemu-devel] [PATCH v4 04/11] acpi: add acpi_pm1_evt_write_en, Gerd Hoffmann, 2012/02/09
- [Qemu-devel] [PATCH v4 01/11] acpi: move around structs, Gerd Hoffmann, 2012/02/09
- [Qemu-devel] [PATCH v4 09/11] suspend: make serial ports wakeup the guest., Gerd Hoffmann, 2012/02/09
- [Qemu-devel] [PATCH v4 10/11] suspend: make rtc alarm wakeup the guest., Gerd Hoffmann, 2012/02/09
- [Qemu-devel] [PATCH v4 05/11] suspend: add infrastructure, Gerd Hoffmann, 2012/02/09
[Qemu-devel] [PATCH v4 08/11] suspend: make ps/2 devices wakeup the guest, Gerd Hoffmann, 2012/02/09
[Qemu-devel] [PATCH v4 11/11] suspend: pmtimer s3 wakeup, Gerd Hoffmann, 2012/02/09
[Qemu-devel] [PATCH v4 06/11] suspend: switch acpi s3 to new infrastructure., Gerd Hoffmann, 2012/02/09
[Qemu-devel] [PATCH 12/11] suspend: add qmp events, Gerd Hoffmann, 2012/02/10