Hi Sergey,
Thanks for all your work here. This is a long-standing problem, and
I'm glad you're working on it.
On Mon, Mar 11, 2019 at 04:31:02PM +0300, Sergey Miroshnichenko wrote:
> If BAR movement has happened (due to PCIe hotplug) after pci_save_state(),
> the saved addresses will become outdated. Restore them the most recently
> calculated values, not the ones stored in an arbitrary moment.
Maybe pci_save_state() should not even save BAR values, since we have
no mechanism to determine whether those saved values are valid?
> Signed-off-by: Sergey Miroshnichenko <s.miroshnichenko@xxxxxxxxx>
> ---
> drivers/pci/pci.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 7c1b362f599a..f006068be209 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -1376,7 +1376,7 @@ static void pci_restore_config_space(struct pci_dev *pdev)
> if (pdev->hdr_type == PCI_HEADER_TYPE_NORMAL) {
> pci_restore_config_space_range(pdev, 10, 15, 0, false);
> /* Restore BARs before the command register. */
> - pci_restore_config_space_range(pdev, 4, 9, 10, false);
> + pci_restore_bars(pdev);
pci_restore_bars() is a much longer call path than
pci_restore_config_space_range(), so it's a little bit scary just from
the complexity point of view, but I think this does make sense.
But I am concerned that we don't handle bridge BARs the same way (this
is an existing problem, not something you're introducing).
Bridge BARs (if implemented) are dwords 4 and 5, so they are currently
restored as part of this range:
pci_restore_config_space_range(pdev, 0, 8, 0, false);
If we followed the same pattern as for type 0 devices, this would look
like:
pci_restore_config_space_range(pdev, 6, 8, 0, false);
pci_restore_config_space_range(pdev, 4, 5, 10, false); /* BARs */
pci_restore_config_space_range(pdev, 0, 3, 0, false);
And after your patch, it would look like:
pci_restore_config_space_range(pdev, 6, 8, 0, false);
pci_restore_bars(pdev);
pci_restore_config_space_range(pdev, 0, 3, 0, false);
I think this would require a little enhancement in pci_restore_bars()
to filter the BAR range based on the hdr_type.
I would propose
- adding a new patch to split up the bridge restore so the (0, 8)
range is split into (6, 8); (4, 5); (0, 3), so it matches the type
0 restore.
- adding another new patch to filter the BAR range in
pci_restore_bars().
- updating this patch to use pci_restore_bars() in both the type 0
and type 1 paths.
- possibly adding a patch to make pci_save_state() not save BAR
values in dev->saved_config_space, and any other changes needed to
stop reading BARs from that area.
What do you think?
> pci_restore_config_space_range(pdev, 0, 3, 0, false);
> } else if (pdev->hdr_type == PCI_HEADER_TYPE_BRIDGE) {
> pci_restore_config_space_range(pdev, 12, 15, 0, false);
> --
> 2.20.1
>
