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由 FUJITA Tomonori 提交于
This reverts: commit bee44f29 Author: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> Date: Fri Sep 12 19:42:35 2008 +0900 x86: make GART to respect device's dma_mask about virtual mappings I wrote the above commit to fix a GART alloc_coherent regression, that can't handle a device having dma_masks > 24bit < 32bits, introduced by the alloc_coherent rewrite: http://lkml.org/lkml/2008/8/12/200 After the alloc_coherent rewrite, GART alloc_coherent tried to allocate pages with GFP_DMA32. If GART got an address that a device can't access to, GART mapped the address to a virtual I/O address. But GART mapping mechanism didn't take account of dma mask, so GART could use a virtual I/O address that the device can't access to again. Alan pointed out: " This is indeed a specific problem found with things like older AACRAID where control blocks must be below 31bits and the GART is above 0x80000000. " The above commit modified GART mapping mechanism to take care of dma mask. But Andi pointed out, "The GART is somewhere in the 4GB range so you cannot use it to map anything < 4GB. Also GART is pretty small." http://lkml.org/lkml/2008/9/12/43 That means it's possible that GART doesn't have virtual I/O address space that a device can access to. The above commit (to modify GART mapping mechanism to take care of dma mask) can't fix the regression reliably so let's avoid making GART more complicated. We need a solution that always works for dma_masks > 24bit < 32bits. That's how GART worked before the alloc_coherent rewrite. Signed-off-by: NFUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> Acked-by: NJoerg Roedel <joerg.roedel@amd.com> Acked-by: NAlan Cox <alan@redhat.com> Signed-off-by: NIngo Molnar <mingo@elte.hu>
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