Re: [RFC PATCH 4/6] x86: PCI: preserve IORESOURCE_STARTALIGN alignment

Ilpo Järvinen
2024-07-10T14:05:50Z

On Tue, 9 Jul 2024, Stewart Hildebrand wrote:

> Currently, it's not possible to use the IORESOURCE_STARTALIGN flag on
> x86 due to the alignment being overwritten in
> pcibios_allocate_dev_resources(). Make one small change in arch/x86 to
> make it work on x86.
>
> Signed-off-by: Stewart Hildebrand <stewart.hildebrand@amd.com>
> ---
> RFC: We don't have enough info in this function to re-calculate the
> alignment value in case of IORESOURCE_STARTALIGN. Luckily our
> alignment value seems to be intact, so just don't touch it...
> Alternatively, we could call pci_reassigndev_resource_alignment()
> after the loop. Would that be preferable?
> ---
> arch/x86/pci/i386.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/pci/i386.c b/arch/x86/pci/i386.c
> index f2f4a5d50b27..ff6e61389ec7 100644
> --- a/arch/x86/pci/i386.c
> +++ b/arch/x86/pci/i386.c
> @@ -283,8 +283,11 @@ static void pcibios_allocate_dev_resources(struct pci_dev *dev, int pass)
> /* We'll assign a new address later */
> pcibios_save_fw_addr(dev,
> idx, r->start);
> - r->end -= r->start;
> - r->start = 0;
> + if (!(r->flags &
> + IORESOURCE_STARTALIGN)) {
> + r->end -= r->start;
> + r->start = 0;
> + }
> }
> }
> }
>

As a general comment to that loop in pcibios_allocate_dev_resources()
function, it would be nice to reverse some of the logic in the if
conditions and use continue to limit the runaway indentation level.

--
i.