On Fri, May 25, 2012 at 12:37 PM, Bjorn Helgaas <bhelgaas@xxxxxxxxxx> wrote:
> On Fri, May 25, 2012 at 11:39:26AM -0700, Yinghai Lu wrote:
>> On Fri, May 25, 2012 at 10:53 AM, Yinghai Lu <yinghai@xxxxxxxxxx> wrote:
>> >> I don't really like the dependency on PCIBIOS_MAX_MEM_32 + 1ULL
>> >> overflowing to zero -- that means the reader has to know what the
>> >> value of PCIBIOS_MAX_MEM_32 is, and things would break in non-obvious
>> >> ways if we changed it.
>> >>
>>
>> please check if attached one is more clear.
>>
>> make max and bottom is only related to _MEM and not default one.
>>
>> - if (!(res->flags & IORESOURCE_MEM_64))
>> - max = PCIBIOS_MAX_MEM_32;
>> + if (res->flags & IORESOURCE_MEM) {
>> + if (!(res->flags & IORESOURCE_MEM_64))
>> + max = PCIBIOS_MAX_MEM_32;
>> + else if (PCIBIOS_MAX_MEM_32 != -1)
>> + bottom = (resource_size_t)(1ULL<<32);
>> + }
>>
>> will still not affect to other arches.
>
> That's goofy. You're proposing to make only x86_64 and x86-PAE try to put
> 64-bit BARs above 4GB. Why should this be specific to x86? I acknowledge
> that there's risk in doing this, but if it's a good idea for x86_64, it
> should also be a good idea for other 64-bit architectures.
>
> And testing for "is this x86_32 without PAE?" with
> "PCIBIOS_MAX_MEM_32 == -1" is just plain obtuse and hides an
> important bit of arch-specific behavior.
>
> Tangential question about allocate_resource(): Is its "max" argument
> really necessary? We'll obviously only allocate from inside the root
> resource, so "max" is just a way to artificially avoid the end of
> that resource. Is there really a case where that's required?
>
> "min" makes sense because in a case like this, it's valid to allocate from
> anywhere in the root resource, but we want to try to allocate from the >4GB
> part first, then fall back to allocating from the whole resource. I'm not
> sure there's a corresponding case for "max."
>
> Getting back to this patch, I don't think we should need to adjust "max" at
> all. For example, this:
>
> commit cb1c8e46244cfd84a1a2fe91be860a74c1cf4e25
> Author: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> Date: Thu May 24 22:15:26 2012 -0600
>
> PCI: try to allocate 64-bit mem resources above 4GB
>
> If we have a 64-bit mem resource, try to allocate it above 4GB first. If
> that fails, we'll fall back to allocating space below 4GB.
>
> diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
> index 4ce5ef2..075e5b1 100644
> --- a/drivers/pci/bus.c
> +++ b/drivers/pci/bus.c
> @@ -121,14 +121,16 @@ pci_bus_alloc_resource(struct pci_bus *bus, struct resource *res,
> {
> int i, ret = -ENOMEM;
> struct resource *r;
> - resource_size_t max = -1;
> + resource_size_t start = 0;
> + resource_size_t end = MAX_RESOURCE;
yeah, MAX_RESOURCE is better than -1.
>
> type_mask |= IORESOURCE_IO | IORESOURCE_MEM;
>
> - /* don't allocate too high if the pref mem doesn't support 64bit*/
> - if (!(res->flags & IORESOURCE_MEM_64))
> - max = PCIBIOS_MAX_MEM_32;
can not remove this one.
otherwise will could allocate above 4g range to non MEM64 resource.
> + /* If this is a 64-bit mem resource, try above 4GB first */
> + if (res->flags & IORESOURCE_MEM_64)
> + start = (resource_size_t) (1ULL << 32);
could affect other arches. let's see if other arches is ok.
please check merged version.
also we have
include/linux/range.h:#define MAX_RESOURCE ((resource_size_t)~0)
arch/x86/kernel/e820.c:#define MAX_RESOURCE_SIZE ((resource_size_t)-1)
we should merge them later?
Thanks
Yinghai
Attachment:
allocate_high_at_first_v3.patch
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