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SubjectRe: [PATCH 5/5] dma-direct: always allow dma mask <= physiscal memory size
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On 19/11/2018 14:18, Ramon Fried wrote:
> On Tue, Oct 9, 2018 at 8:02 AM Benjamin Herrenschmidt
> <benh@kernel.crashing.org> wrote:
>>
>> On Wed, 2018-10-03 at 16:10 -0700, Alexander Duyck wrote:
>>>> - * Because 32-bit DMA masks are so common we expect every architecture
>>>> - * to be able to satisfy them - either by not supporting more physical
>>>> - * memory, or by providing a ZONE_DMA32. If neither is the case, the
>>>> - * architecture needs to use an IOMMU instead of the direct mapping.
>>>> - */
>>>> - if (mask < phys_to_dma(dev, DMA_BIT_MASK(32)))
>>>> + u64 min_mask;
>>>> +
>>>> + if (IS_ENABLED(CONFIG_ZONE_DMA))
>>>> + min_mask = DMA_BIT_MASK(ARCH_ZONE_DMA_BITS);
>>>> + else
>>>> + min_mask = DMA_BIT_MASK(32);
>>>> +
>>>> + min_mask = min_t(u64, min_mask, (max_pfn - 1) << PAGE_SHIFT);
>>>> +
>>>> + if (mask >= phys_to_dma(dev, min_mask))
>>>> return 0;
>>>> -#endif
>>>> return 1;
>>>> }
>>>
>>> So I believe I have run into the same issue that Guenter reported. On
>>> an x86_64 system w/ Intel IOMMU. I wasn't able to complete boot and
>>> all probe attempts for various devices were failing with -EIO errors.
>>>
>>> I believe the last mask check should be "if (mask < phys_to_dma(dev,
>>> min_mask))" not a ">=" check.
>>
>> Right, that test is backwards. I needed to change it here too (powermac
>> with the rest of the powerpc series).
>>
>> Cheers,
>> Ben.
>>
>>
>
> Hi, I'm working on a MIPS64 soc with PCIe root complex on it, and it
> appears that this series of patches are causing all PCI drivers that
> request 64bit mask to fail with -5.
> It's broken in 4.19. However, I just checked, it working on master.
> We may need to backport a couple of patches to 4.19. I'm not sure
> though which patches should be backported as there were at least 10
> patches resolving this dma_direct area recently.
> Christoph, Robin.
> Can we ask Greg to backport all these changes ? What do you think ?

As far as I'm aware, the only real issue in 4.19 was my subtle breakage
around setting bus_dma_mask - that's fixed by 6778be4e5209, which
according to my inbox got picked up by autosel for 4.19 stable last week.

Robin.

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