Dave Airlie wrote:
>> hm, i'm missing a description about how this bug was
>> triggered. How did you end up getting highmem pages to a cpa
>> call?
>>
>
> GEM and TTM both allocate page arrays and just pass them to cpa,
> we don't know what type of pages the allocator gives us back and we really
> shouldn't have to, so having cpa ignore highmem pages is certainly the
> right option.
>
> GEM just uses shmem code to alloc the pages and TTM has its own allocator.
>
>
Yes, Dave is right.
Although I'm not 100% sure the TTM code I was using that triggered this
has made it into 2.6.31.
Old AGP uses (GFP_KERNEL | GFP_DMA32 | __GFP_ZERO), which (correct me if
I'm wrong) never hands back highmem pages. This means that Intel's GEM
is the only likely user for 2.6.31.
/Thomas
> Dave.
>
> >
>
>>> else
>>> address = *cpa->vaddr;
>>> @@ -696,9 +699,12 @@ static int cpa_process_alias(struct cpa_data *cpa)
>>> * No need to redo, when the primary call touched the direct
>>> * mapping already:
>>> */
>>> - if (cpa->flags & CPA_PAGES_ARRAY)
>>> - vaddr = (unsigned long)page_address(cpa->pages[cpa->curpage]);
>>> - else if (cpa->flags & CPA_ARRAY)
>>> + if (cpa->flags & CPA_PAGES_ARRAY) {
>>> + struct page *page = cpa->pages[cpa->curpage];
>>> + if (unlikely(PageHighMem(page)))
>>> + return 0;
>>> + vaddr = (unsigned long)page_address(page);
>>> + } else if (cpa->flags & CPA_ARRAY)
>>> vaddr = cpa->vaddr[cpa->curpage];
>>> else
>>> vaddr = *cpa->vaddr;
>>> @@ -1118,7 +1124,9 @@ int set_pages_array_uc(struct page **pages, int
>>> addrinarray)
>>> int free_idx;
>>>
>>> for (i = 0; i < addrinarray; i++) {
>>> - start = (unsigned long)page_address(pages[i]);
>>> + if (PageHighMem(pages[i]))
>>> + continue;
>>> + start = page_to_pfn(pages[i]) << PAGE_SHIFT;
>>> end = start + PAGE_SIZE;
>>> if (reserve_memtype(start, end, _PAGE_CACHE_UC_MINUS, NULL))
>>> goto err_out;
>>>
>> ok, that's a bug introduced in .29 but which was latent until now:
>> drivers/char/agp/generic.c now uses it plus (indirectly) a number of
>> AGP drivers, since:
>>
>> commit 07613ba2f464f59949266f4337b75b91eb610795
>> Author: Dave Airlie <airl...@redhat.com>
>> Date: Fri Jun 12 14:11:41 2009 +1000
>>
>> agp: switch AGP to use page array instead of unsigned long array
>>
>> I dont see how it can end up with highmem pages though. All
>> the graphics apperture allocations happen to lowmem AFAICS.
>> Did GEM add the possibility for user pages (highmem amongst
>> them) ending up in that pool? Which code does that?
>>
>>
>>> @@ -1131,7 +1139,9 @@ int set_pages_array_uc(struct page **pages, int
>>> addrinarray)
>>> err_out:
>>> free_idx = i;
>>> for (i = 0; i < free_idx; i++) {
>>> - start = (unsigned long)page_address(pages[i]);
>>> + if (PageHighMem(pages[i]))
>>> + continue;
>>> + start = page_to_pfn(pages[i]) << PAGE_SHIFT;
>>> end = start + PAGE_SIZE;
>>> free_memtype(start, end);
>>> }
>>> @@ -1160,7 +1170,9 @@ int set_pages_array_wb(struct page **pages, int
>>> addrinarray)
>>> return retval;
>>>
>>> for (i = 0; i < addrinarray; i++) {
>>> - start = (unsigned long)page_address(pages[i]);
>>> + if (PageHighMem(pages[i]))
>>> + continue;
>>> + start = page_to_pfn(pages[i]) << PAGE_SHIFT;
>>> end = start + PAGE_SIZE;
>>> free_memtype(start, end);
>>>
>> In any case it's a must-have fix for .31. Possibly even a backport
>> tag is needed, in case a distro does a .30 kernel with more recent
>> graphics bits.
>>
>> Ingo
>>
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