linux-kernel - RE: [PATCH v2] PCI: PM: Move to D0 before calling pci_legacy_resume

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Date:   Mon, 7 Oct 2019 18:57:38 +0000
From:   Dexuan Cui <decui@...rosoft.com>
To:     Bjorn Helgaas <helgaas@...nel.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
CC:     "lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        Michael Kelley <mikelley@...rosoft.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "driverdev-devel@...uxdriverproject.org" 
        <driverdev-devel@...uxdriverproject.org>,
        Sasha Levin <Alexander.Levin@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        "olaf@...fle.de" <olaf@...fle.de>,
        "apw@...onical.com" <apw@...onical.com>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        vkuznets <vkuznets@...hat.com>,
        "marcelo.cerri@...onical.com" <marcelo.cerri@...onical.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "jackm@...lanox.com" <jackm@...lanox.com>
Subject: RE: [PATCH v2] PCI: PM: Move to D0 before calling
 pci_legacy_resume_early()

> -----Original Message-----
> From: Bjorn Helgaas <helgaas@...nel.org>
> Sent: Monday, October 7, 2019 6:24 AM
> To: Dexuan Cui <decui@...rosoft.com>
> Cc: lorenzo.pieralisi@....com; linux-pci@...r.kernel.org; Michael Kelley
> <mikelley@...rosoft.com>; linux-hyperv@...r.kernel.org;
> linux-kernel@...r.kernel.org; driverdev-devel@...uxdriverproject.org; Sasha
> Levin <Alexander.Levin@...rosoft.com>; Haiyang Zhang
> <haiyangz@...rosoft.com>; KY Srinivasan <kys@...rosoft.com>;
> olaf@...fle.de; apw@...onical.com; jasowang@...hat.com; vkuznets
> <vkuznets@...hat.com>; marcelo.cerri@...onical.com; Stephen Hemminger
> <sthemmin@...rosoft.com>; jackm@...lanox.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.
> >
> > 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.
> >
> > Signed-off-by: Dexuan Cui <decui@...rosoft.com>
> 
> 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?
> 
> > ---
> >
> > changes in v2:
> > 	Updated the changelog with more details.
> >
> >  drivers/pci/pci-driver.c | 7 ++++---
> >  1 file changed, 4 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
> > index 36dbe960306b..27dfc68db9e7 100644
> > --- 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
> >

Added Rafael to "To".

Thanks,
-- Dexuan