linux-kernel - Re: [PATCH 02/11] PCI: Try to allocate mem64 above 4G at first

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Date:	Fri, 25 May 2012 18:12:39 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Steven Newbury <steve@...wbury.org.uk>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 02/11] PCI: Try to allocate mem64 above 4G at first

On Fri, May 25, 2012 at 5:10 PM, Yinghai Lu <yinghai@...nel.org> wrote:
> On Fri, May 25, 2012 at 2:55 PM, Bjorn Helgaas <bhelgaas@...gle.com> wrote:
>> I think we should fix this with a separate patch that removes
>> PCIBIOS_MAX_MEM_32 altogether, replacing this use with an explicit
>> 0xffffffff (or some other "max 32-bit value" symbol).  I don't think
>> there's anything arch-specific about this.
>>
>> So I'd like to see two patches here:
>>  1) Avoid allocating 64-bit regions for 32-bit BARs
>>  2) Try to allocate regions above 4GB for 64-bit BARs
>
> Sure. please check updated two patches.

I think the first one looks good.

I'm curious about the second.  Why did you add the IORESOURCE_MEM
test?  That's doesn't affect the "start =" piece because
IORESOURCE_MEM is always set if IORESOURCE_MEM_64 is set.

But it does affect the "end =" part.  Previously we limited all I/O
and 32-bit mem BARs to the low 4GB.  This patch makes it so we limit
32-bit mem BARs to the low 4GB, but we don't limit I/O BARs.  But I/O
BARs can only have 32 bits of address, so it seems like we should
limit them the same way as 32-bit mem BARs.  So I expected something
like this:

    if (res->flags & IORESOURCE_MEM_64) {
        start = (resource_size_t) (1ULL << 32);
        end = PCI_MAX_RESOURCE;
    } else {
        start = 0;
        end = PCI_MAX_RESOURCE_32;
    }
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