Re: [PATCH 1/2] PCI: fix restoring resized BAR state on resume

[Christian KÃnig]

Am 02.07.2018 um 15:49 schrieb Bjorn Helgaas:
> On Mon, Jul 02, 2018 at 03:20:59PM +0200, Christian KÃnig wrote:
> > Am 30.06.2018 um 02:57 schrieb Bjorn Helgaas:
> > > On Thu, Jun 14, 2018 at 02:21:45PM +0200, Christian KÃnig wrote:
> > > > Resize BARs after resume to the expected size again.
> > > >
> > > > Signed-off-by: Christian KÃnig <christian.koenig@xxxxxxx>
> > > > BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=199959
> > > > CC: stable@xxxxxxxxxxxxxxx      # v4.15+
> > > I applied both of these to pci/resource for v4.19, thanks!  It'd be nice to
> > > have them in v4.18, but since it's not a regression and the problem has
> > > been there since v4.15, I'm not sure I could justify it.
> > Well it is a regression. The change to enable this in the upstream driver
> > was added in 4.16, but a good bunch of people also compile our backported
> > DKMS module.
> >
> > And now those people are complaining that the driver stopped working after
> > resume in 4.15 with the DKMS module and with 4.16 with the upstream module.
> >
> > Alternatively I can disable resizing from the driver from kernels older than
> > v4.19.
> Feel free to help justify including this in v4.18 by providing the
> details of the regression and the relevant commits.  If this is
> something that worked in v4.17, and some commit we merged for
> v4.18-rc1 broke it, it would be a slam dunk to include the fix for
> v4.18.  I took a quick look through the commits we added in v4.18-rc1
> but didn't see anything obvious.
>
> Obviously, putting a fix in v4.18 doesn't help the people running
> v4.15 or v4.16.  The stable backports *will* help with that, and we
> already have the tag for that.
>
> The current trajectory we're on is that these are headed for
> v4.19-rc1, and soon after they appear there, they will be backported
> to the v4.15-v4.18 stable kernels.

Ah! Thanks for the explanation on how fixes flow into stable kernels and 
you are right it's indeed not a regression in 4.18.

In this case everything is fine and the backports to stable kernels 
should handle that.

Thanks,
Christian.

> Bjorn
>
> > > > ---
> > > >    drivers/pci/pci.c | 28 ++++++++++++++++++++++++++++
> > > >    1 file changed, 28 insertions(+)
> > > >
> > > > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> > > > index bd6f156dc3cf..d4685090378b 100644
> > > > --- a/drivers/pci/pci.c
> > > > +++ b/drivers/pci/pci.c
> > > > @@ -1159,6 +1159,33 @@ static void pci_restore_config_space(struct pci_dev *pdev)
> > > >    	}
> > > >    }
> > > > +static void pci_restore_rebar_state(struct pci_dev *pdev)
> > > > +{
> > > > +	unsigned int pos, nbars, i;
> > > > +	u32 ctrl;
> > > > +
> > > > +	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_REBAR);
> > > > +	if (!pos)
> > > > +		return;
> > > > +
> > > > +	pci_read_config_dword(pdev, pos + PCI_REBAR_CTRL, &ctrl);
> > > > +	nbars = (ctrl & PCI_REBAR_CTRL_NBAR_MASK) >>
> > > > +		    PCI_REBAR_CTRL_NBAR_SHIFT;
> > > > +
> > > > +	for (i = 0; i < nbars; i++, pos += 8) {
> > > > +		struct resource *res;
> > > > +		int bar_idx, size;
> > > > +
> > > > +		pci_read_config_dword(pdev, pos + PCI_REBAR_CTRL, &ctrl);
> > > > +		bar_idx = ctrl & PCI_REBAR_CTRL_BAR_IDX;
> > > > +		res = pdev->resource + bar_idx;
> > > > +		size = order_base_2((resource_size(res) >> 20) | 1) - 1;
> > > > +		ctrl &= ~PCI_REBAR_CTRL_BAR_SIZE;
> > > > +		ctrl |= size << 8;
> > > > +		pci_write_config_dword(pdev, pos + PCI_REBAR_CTRL, ctrl);
> > > > +	}
> > > > +}
> > > > +
> > > >    /**
> > > >     * pci_restore_state - Restore the saved state of a PCI device
> > > >     * @dev: - PCI device that we're dealing with
> > > > @@ -1174,6 +1201,7 @@ void pci_restore_state(struct pci_dev *dev)
> > > >    	pci_restore_pri_state(dev);
> > > >    	pci_restore_ats_state(dev);
> > > >    	pci_restore_vc_state(dev);
> > > > +	pci_restore_rebar_state(dev);
> > > >    	pci_cleanup_aer_error_status_regs(dev);
> > > > --
> > > > 2.14.1