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Message-ID: <35f54983-4209-40bd-aad0-f34c97f4a8b1@redhat.com> Date: Mon, 18 Dec 2023 12:41:08 +0100 From: David Hildenbrand <david@...hat.com> To: David Stevens <stevensd@...omium.org> Cc: "Michael S . Tsirkin" <mst@...hat.com>, Jason Wang <jasowang@...hat.com>, virtualization@...ts.linux-foundation.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH v2] virtio: Add support for no-reset virtio PCI PM On 15.12.23 02:00, David Stevens wrote: > On Thu, Dec 14, 2023 at 6:47 PM David Hildenbrand <david@...hat.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@...omium.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@...0 ~]# echo "s2idle" > /sys/power/mem_sleep >> [root@...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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