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Wysocki" Cc: Dexuan Cui , "lorenzo.pieralisi@arm.com" , "linux-pci@vger.kernel.org" , Michael Kelley , "linux-hyperv@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "driverdev-devel@linuxdriverproject.org" , Sasha Levin , Haiyang Zhang , KY Srinivasan , "olaf@aepfle.de" , "apw@canonical.com" , "jasowang@redhat.com" , vkuznets , "marcelo.cerri@canonical.com" , Stephen Hemminger , "jackm@mellanox.com" Subject: Re: [PATCH v2] PCI: PM: Move to D0 before calling pci_legacy_resume_early() Message-ID: <20191008195624.GA198287@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Tue, Oct 08, 2019 at 07:32:27PM +0200, Rafael J. Wysocki wrote: > On 10/7/2019 8:57 PM, Dexuan Cui wrote: > > > -----Original Message----- > > > From: Bjorn Helgaas > > > Sent: Monday, October 7, 2019 6:24 AM > > > To: Dexuan Cui > > > Cc: lorenzo.pieralisi@arm.com; linux-pci@vger.kernel.org; Michael Kelley > > > ; linux-hyperv@vger.kernel.org; > > > linux-kernel@vger.kernel.org; driverdev-devel@linuxdriverproject.org; Sasha > > > Levin ; Haiyang Zhang > > > ; KY Srinivasan ; > > > olaf@aepfle.de; apw@canonical.com; jasowang@redhat.com; vkuznets > > > ; marcelo.cerri@canonical.com; Stephen Hemminger > > > ; jackm@mellanox.com > > > Subject: Re: [PATCH v2] PCI: PM: Move to D0 before calling > > > pci_legacy_resume_early() > > > > > > On Wed, Aug 14, 2019 at 01:06:55AM +0000, Dexuan Cui wrote: > > > > In pci_legacy_suspend_late(), the device state is moved to PCI_UNKNOWN. > > > > > > > > In pci_pm_thaw_noirq(), the state is supposed to be moved back to PCI_D0, > > > > but the current code misses the pci_legacy_resume_early() path, so the > > > > state remains in PCI_UNKNOWN in that path. As a result, in the resume > > > > phase of hibernation, this causes an error for the Mellanox VF driver, > > > > which fails to enable MSI-X because pci_msi_supported() is false due > > > > to dev->current_state != PCI_D0: > > > > > > > > mlx4_core a6d1:00:02.0: Detected virtual function - running in slave mode > > > > mlx4_core a6d1:00:02.0: Sending reset > > > > mlx4_core a6d1:00:02.0: Sending vhcr0 > > > > mlx4_core a6d1:00:02.0: HCA minimum page size:512 > > > > mlx4_core a6d1:00:02.0: Timestamping is not supported in slave mode > > > > mlx4_core a6d1:00:02.0: INTx is not supported in multi-function mode, > > > aborting > > > > PM: dpm_run_callback(): pci_pm_thaw+0x0/0xd7 returns -95 > > > > PM: Device a6d1:00:02.0 failed to thaw: error -95 > > > > > > > > To be more accurate, the "resume" phase means the "thaw" callbacks which > > > > run before the system enters hibernation: when the user runs the command > > > > "echo disk > /sys/power/state" for hibernation, first the kernel "freezes" > > > > all the devices and creates a hibernation image, then the kernel "thaws" > > > > the devices including the disk/NIC, writes the memory to the disk, and > > > > powers down. This patch fixes the error message for the Mellanox VF driver > > > > in this phase. Wordsmithing nit: what the patch does is not "fix the error message"; what it does is fix the *problem*, i.e., the fact that we can't operate the device because we can't enable MSI-X. The message is only a symptom. IIUC the relevant part of the system hibernation sequence is: pci_pm_freeze_noirq pci_pm_thaw_noirq pci_pm_thaw And the execution flow is: pci_pm_freeze_noirq if (pci_has_legacy_pm_support(pci_dev)) # true for mlx4 pci_legacy_suspend_late(dev, PMSG_FREEZE) pci_pm_set_unknown_state dev->current_state = PCI_UNKNOWN # <--- pci_pm_thaw_noirq if (pci_has_legacy_pm_support(pci_dev)) # true pci_legacy_resume_early(dev) # noop; mlx4 doesn't implement pci_pm_thaw # returns -95 EOPNOTSUPP if (pci_has_legacy_pm_support(pci_dev)) # true pci_legacy_resume drv->resume mlx4_resume # mlx4_driver.resume (legacy) mlx4_load_one mlx4_enable_msi_x pci_enable_msix_range __pci_enable_msix_range __pci_enable_msix if (!pci_msi_supported()) if (dev->current_state != PCI_D0) # <--- return 0 return -EINVAL err = -EOPNOTSUPP "INTx is not supported ..." (These are just my notes; you don't need to put them all into the commit message. I'm just sharing them in case I'm not understanding correctly.) > > > > When the system starts again, a fresh kernel starts to run, and when the > > > > kernel detects that a hibernation image was saved, the kernel "quiesces" > > > > the devices, and then "restores" the devices from the saved image. In this > > > > path: > > > > device_resume_noirq() -> ... -> > > > > pci_pm_restore_noirq() -> > > > > pci_pm_default_resume_early() -> > > > > pci_power_up() moves the device states back to PCI_D0. This path is > > > > not broken and doesn't need my patch. > > > > The cc list suggests that this might be a fix for a user-reported problem. Is there a launchpad or similar link you could include here? Should this be marked for stable? > > > > Signed-off-by: Dexuan Cui > > > This looks like a bugfix for 5839ee7389e8 ("PCI / PM: Force devices to > > > D0 in pci_pm_thaw_noirq()") so maybe it should be marked for stable as > > > 5839ee7389e8 was? > > > > > > Rafael, could you confirm? > > No, it is not a bug fix for that commit.  The underlying issue would be > there without that commit too. Oh, right, I dunno what I was thinking, sorry. > > > > --- a/drivers/pci/pci-driver.c > > > > +++ b/drivers/pci/pci-driver.c > > > > @@ -1074,15 +1074,16 @@ static int pci_pm_thaw_noirq(struct device > > > *dev) > > > > return error; > > > > } > > > > > > > > - if (pci_has_legacy_pm_support(pci_dev)) > > > > - return pci_legacy_resume_early(dev); > > > > - > > > > /* > > > > * pci_restore_state() requires the device to be in D0 (because of MSI > > > > * restoration among other things), so force it into D0 in case the > > > > * driver's "freeze" callbacks put it into a low-power state directly. > > > > */ > > > > pci_set_power_state(pci_dev, PCI_D0); > > > > + > > > > + if (pci_has_legacy_pm_support(pci_dev)) > > > > + return pci_legacy_resume_early(dev); > > > > + > > > > pci_restore_state(pci_dev); > > > > > > > > if (drv && drv->pm && drv->pm->thaw_noirq) > > > > -- > > > > 2.19.1 > > > > > The patch looks reasonable to me, but the comment above the > pci_set_power_state() call needs to be updated too IMO. Hmm. 1) pci_restore_state() mainly writes config space, which doesn't require the device to be in D0. The only thing I see that would require D0 is the MSI-X MMIO space, so to be more specific, the comment could say "restoring the MSI-X *MMIO* state requires the device to be in D0". But I think you meant some other comment change. Did you mean something along the lines of "a legacy drv->resume_early() callback and pci_restore_state() both require the device to be in D0"? If something else, maybe you could propose some text? 2) I assume pci_pm_thaw_noirq() should leave the device in a functionally equivalent state, whether it uses legacy PM or not. Do we want something like the patch below instead? If we *do* want to skip pci_restore_state() for legacy PM, maybe we should add a comment. 3) Documentation/power/pci.rst says: ... devices have to be brought back to the fully functional state ... pci_pm_thaw_noirq() ... doesn't put the device into the full power state and doesn't attempt to restore its standard configuration registers. That doesn't seem consistent, and it looks like pci_pm_thaw_noirq() actually *does* put the device in full power (D0) state and restore config registers. diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c index a8124e47bf6e..30c721fd6bcf 100644 --- a/drivers/pci/pci-driver.c +++ b/drivers/pci/pci-driver.c @@ -1068,7 +1068,7 @@ static int pci_pm_thaw_noirq(struct device *dev) { struct pci_dev *pci_dev = to_pci_dev(dev); struct device_driver *drv = dev->driver; - int error = 0; + int error; if (pcibios_pm_ops.thaw_noirq) { error = pcibios_pm_ops.thaw_noirq(dev); @@ -1076,9 +1076,6 @@ static int pci_pm_thaw_noirq(struct device *dev) return error; } - if (pci_has_legacy_pm_support(pci_dev)) - return pci_legacy_resume_early(dev); - /* * pci_restore_state() requires the device to be in D0 (because of MSI * restoration among other things), so force it into D0 in case the @@ -1087,10 +1084,13 @@ static int pci_pm_thaw_noirq(struct device *dev) pci_set_power_state(pci_dev, PCI_D0); pci_restore_state(pci_dev); + if (pci_has_legacy_pm_support(pci_dev)) + return pci_legacy_resume_early(dev); + if (drv && drv->pm && drv->pm->thaw_noirq) - error = drv->pm->thaw_noirq(dev); + return drv->pm->thaw_noirq(dev); - return error; + return 0; } static int pci_pm_thaw(struct device *dev)