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

Stewart Hildebrand
2024-07-15T17:30:46Z

On 7/10/24 10:05, Ilpo Järvinen wrote:
> 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.

The similar function pcibios_allocate_resources() in
arch/powerpc/kernel/pci-common.c has moved some of the logic out into a
separate function. I'll do the same here.