Re: [PATCH]: PCI: GART iommu alignment fixes [v2]

[Prarit Bhargava <prarit@redhat.com>]

>>>  
>>
>> Yeah, I'm not against fixing IOMMUs to make alloc_consistent return
>> the reqeuested size aligned memory. My point is that it's not likely
>> to fix anything. Even with the patch, we hit the above problem because
>> as I explained, the root cause of the problem is the boundary issue;
>> we need to fix pci-dma.c
>>
>>   
>
> Sorry, I misquoted code up there and was looking for a clear example 
> of where this would happen.  The issue I'm trying to resolve didn't 
> happen on the skge -- it was just a convenient piece of code to 
> examine and point out ;)
>

Here's a case where USB has problems:

 BIOS-e820: 0000000000000000 - 000000000009f400 (usable)
 BIOS-e820: 000000000009f400 - 00000000000a0000 (reserved)
 BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
 BIOS-e820: 0000000000100000 - 00000000f57f6800 (reserved)
 BIOS-e820: 00000000f57f6800 - 00000000f5800000 (ACPI data)
 BIOS-e820: 00000000f5800000 - 00000000fdc00000 (reserved)
 BIOS-e820: 00000000fdc00000 - 00000000fdc01000 (reserved)
 BIOS-e820: 00000000fdc10000 - 00000000fdc01000 (reserved)
 BIOS-e820: 00000000fdc20000 - 00000000fdc01000 (reserved)
 BIOS-e820: 00000000fdc30000 - 00000000fdc01000 (reserved)
 BIOS-e820: 00000000fec00000 - 00000000fec10000 (reserved)
 BIOS-e820: 00000000fec10000 - 00000000fec20000 (reserved)
 BIOS-e820: 00000000fec20000 - 00000000fec30000 (reserved)
 BIOS-e820: 00000000fee00000 - 00000000fee10000 (reserved)
 BIOS-e820: 00000000fee10000 - 00000000ff800000 (reserved)
 BIOS-e820: 00000000ff800000 - 0000000100000000 (reserved)
 BIOS-e820: 0000000100000000 - 00000017fffff000 (usable)

I haven't tracked down what pci_alloc_consistent went wrong in 
usb-storage yet ... it seemed irrelevant because GART was broken.

P.