On Mon, Jun 25, 2012 at 2:54 PM, Nikhil P Rao <nikhil.rao@xxxxxxxxx> wrote:
> On Sat, 2012-06-23 at 12:15 -0600, Bjorn Helgaas wrote:
>> On Thu, Jun 21, 2012 at 5:47 PM, Nikhil P Rao <nikhil.rao@xxxxxxxxx> wrote:
>> > I ran into the "disabling BAR .." error message when
>> > trying to use a 8Gb PCIe card on a system with a BIOS
>> > that didnt have support for BAR size > 2Gb.
>>
>> So the BIOS left the 8Gb BAR unassigned, and you got the "disabling
>> BAR ... (bad alignment)" message when Linux tried to enable it?
>
> Yes.
>
>> How do we know 8Gb is the correct new limit? Are we going to be
>> fixing this again when we see a 16Gb or a 32Gb BAR? Do we need a
>> better algorithm that doesn't have a limit like this?
>>
>
> The original error message seems applicable to 32bit archs. and not to
> 64 bit archs. How about the patch below - is aligns[44] (256bytes more)
> acceptable ?
>
>
> From: Nikhil P Rao <nikhil.rao@xxxxxxxxx>
> Date: Mon, 25 Jun 2012 13:33:55 -0700
> Subject: [PATCH] pci: fix resource size check
>
> Support a PCI BAR alignment of > 2Gb, the original check was
> only applicable to 32 bit kernels,
>
> Signed-off-by: Nikhil P Rao <nikhil.rao@xxxxxxxxx>
> ---
> drivers/pci/setup-bus.c | 5 +++--
> 1 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
> index 8fa2d4b..9f8d9ea 100644
> --- a/drivers/pci/setup-bus.c
> +++ b/drivers/pci/setup-bus.c
> @@ -780,7 +780,7 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
> {
> struct pci_dev *dev;
> resource_size_t min_align, align, size, size0, size1;
> - resource_size_t aligns[12]; /* Alignments from 1Mb to 2Gb */
> + resource_size_t aligns[44]; /* Alignments from 1Mb to 2^63 */
> int order, max_order;
> struct resource *b_res = find_free_bus_resource(bus, type);
> unsigned int mem64_mask = 0;
> @@ -819,7 +819,8 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
> /* For bridges size != alignment */
> align = pci_resource_alignment(dev, r);
> order = __ffs(align) - 20;
> - if (order > 11) {
> + if ((sizeof(size_t) == 4 && order > 11) ||
> + (sizeof(size_t) == 8 && order > 43)) {
> dev_warn(&dev->dev, "disabling BAR %d: %pR "
> "(bad alignment %#llx)\n", i, r,
> (unsigned long long) align);
Yinghai, what's your opinion on this? The aligns[] array on the stack
is currently 96 bytes and would grow to 352 with this patch, which
does seem like quite a bit.
I do think the 2GB limit here is out-of-date.
Bjorn
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