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SubjectRe: [PATCH v2] virtio: Add support for no-reset virtio PCI PM
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On 15.12.23 02:00, David Stevens wrote:
> On Thu, Dec 14, 2023 at 6:47 PM David Hildenbrand <david@redhat.com> wrote:
>>
>> On 08.12.23 08:07, David Stevens wrote:
>>> If a virtio_pci_device supports native PCI power management and has the
>>> No_Soft_Reset bit set, then skip resetting and reinitializing the device
>>> when suspending and restoring the device. This allows system-wide low
>>> power states like s2idle to be used in systems with stateful virtio
>>> devices that can't simply be re-initialized (e.g. virtio-fs).
>>>
>>> Signed-off-by: David Stevens <stevensd@chromium.org>
>>> ---
>>> v1 -> v2:
>>> - Check the No_Soft_Reset bit
>>>
>>> drivers/virtio/virtio_pci_common.c | 34 +++++++++++++++++++++++++++++-
>>> 1 file changed, 33 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
>>> index c2524a7207cf..3a95ecaf12dc 100644
>>> --- a/drivers/virtio/virtio_pci_common.c
>>> +++ b/drivers/virtio/virtio_pci_common.c
>>> @@ -492,8 +492,40 @@ static int virtio_pci_restore(struct device *dev)
>>> return virtio_device_restore(&vp_dev->vdev);
>>> }
>>>
>>> +static bool vp_supports_pm_no_reset(struct device *dev)
>>> +{
>>> + struct pci_dev *pci_dev = to_pci_dev(dev);
>>> + u16 pmcsr;
>>> +
>>> + if (!pci_dev->pm_cap)
>>> + return false;
>>> +
>>> + pci_read_config_word(pci_dev, pci_dev->pm_cap + PCI_PM_CTRL, &pmcsr);
>>> + if (PCI_POSSIBLE_ERROR(pmcsr)) {
>>> + dev_err(dev, "Unable to query pmcsr");
>>> + return false;
>>> + }
>>> +
>>> + return pmcsr & PCI_PM_CTRL_NO_SOFT_RESET;
>>> +}
>>> +
>>> +static int virtio_pci_suspend(struct device *dev)
>>> +{
>>> + return vp_supports_pm_no_reset(dev) ? 0 : virtio_pci_freeze(dev);
>>> +}
>>> +
>>> +static int virtio_pci_resume(struct device *dev)
>>> +{
>>> + return vp_supports_pm_no_reset(dev) ? 0 : virtio_pci_restore(dev);
>>> +}
>>> +
>>> static const struct dev_pm_ops virtio_pci_pm_ops = {
>>> - SET_SYSTEM_SLEEP_PM_OPS(virtio_pci_freeze, virtio_pci_restore)
>>> + .suspend = virtio_pci_suspend,
>>> + .resume = virtio_pci_resume,
>>> + .freeze = virtio_pci_freeze,
>>> + .thaw = virtio_pci_restore,
>>> + .poweroff = virtio_pci_freeze,
>>> + .restore = virtio_pci_restore,
>>> };
>>> #endif
>>>
>>
>> Am I correct with my assumption that this will make s2idle work with virtio-mem-pci as well?
>>
>> Right now, all suspending is disabled, but really only s4/hibernate is problematic.
>>
>> [root@vm-0 ~]# echo "s2idle" > /sys/power/mem_sleep
>> [root@vm-0 ~]# echo "mem" > /sys/power/state
>> [ 101.822991] PM: suspend entry (s2idle)
>> [ 101.828978] Filesystems sync: 0.004 seconds
>> [ 101.831618] Freezing user space processes
>> [ 101.834569] Freezing user space processes completed (elapsed 0.001 seconds)
>> [ 101.836915] OOM killer disabled.
>> [ 101.838072] Freezing remaining freezable tasks
>> [ 101.841054] Freezing remaining freezable tasks completed (elapsed 0.001 seconds)
>> [ 101.843538] printk: Suspending console(s) (use no_console_suspend to debug)
>> [ 101.957676] virtio_mem virtio0: save/restore not supported.
>> [ 101.957683] virtio-pci 0000:00:02.0: PM: pci_pm_suspend(): virtio_pci_freeze+0x0/0x50 returns -1
>> [ 101.957702] virtio-pci 0000:00:02.0: PM: dpm_run_callback(): pci_pm_suspend+0x0/0x170 returns -1
>> [ 101.957718] virtio-pci 0000:00:02.0: PM: failed to suspend async: error -1
>
> QEMU's virtio-pci devices don't advertise no_soft_reset, so this patch
> won't affect vanilla QEMU. But if you add PCI_PM_CTRL_NO_SOFT_RESET to
> the capability, then it should work. I'm working with crosvm, which
> doesn't have virtio-mem implemented, but this patch makes virtio-fs
> work with no extra kernel changes.

Thanks for the explanation, makes sense to me.

--
Cheers,

David / dhildenb


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