ACK: [SRU][F/E][aws][PATCH v2 0/1] aws: disable CONFIG_DMA_CMA
Kleber Souza
kleber.souza at canonical.com
Fri May 29 06:36:59 UTC 2020
On 2020-05-22 15:34, Andrea Righi wrote:
> BugLink: https://bugs.launchpad.net/bugs/1879711
>
> [Impact]
>
> The option CONFIG_DMA_CMA seems to cause hibernation failures on the
> t2.* instance types (Xen).
>
> With this option enabled device drivers are allowed to use the
> Contiguous Memory Allocator (CMA) for DMA operations. So, drivers can
> allocate large physically-contiguous blocks of memory, instead of
> relying on the I/O map or scatter-gather support.
>
> However, on resume, the memory used by DMA needs to be re-initialized /
> re-allocated, but it may fail to allocate large chunks of contiguous
> memory due to the fact that we also need to restore the hibernation
> image, using more memory and causing a system hang during the resume
> process.
>
> [Test case]
>
> Hibernate / resume any t2.* instance (especially t2.nano, where the
> problem seems to happen 100% of the times after 2 consecutive
> hibernate/resume cycles).
>
> [Fix]
>
> Disable CONFIG_DMA_CMA on amd64 and re-align config and annotations file
> with master kernel.
>
> NOTE: this option is already disabled in the generic kernel (see LP:
> #1362261).
>
> With this option disabled the success rate of hibernation on the t2.*
> instance types during our tests jumped to 100%.
>
> [Regression potential]
>
> It is a .config change, no regression potential except for the fact that
> disabling this option also disables the module 'etnaviv' (Vivante
> graphic card), that is not really needed in the aws kernel.
>
> Changes in v2:
> - disable CONFIG_DMA_CMA only on amd64 and re-align annotations file
> with master kernel
> - provide patch for eoan:linux-aws
>
>
Acked-by: Kleber Sacilotto de Souza <kleber.souza at canonical.com>
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