Re: [PATCH 2/4] iommu/arm-smmu-v3: Document MMU-700 erratum 2812531

[Nicolin Chen <nicolinc@nvidia.com>]

On Wed, May 10, 2023 at 11:12:05AM -0700, Nicolin Chen wrote:
> On Wed, May 10, 2023 at 04:38:44PM +0100, Robin Murphy wrote:
> 
> > To work around MMU-700 erratum 2812531 we need to ensure that certain
> > sequences of commands cannot be issued without an intervening sync. In
> > practice this falls out of our current command-batching machinery
> > anyway - each batch only contains a single type of invalidation command,
> 
> Hmm. This doesn't apply to the user cache invalidation solution
> in my v2. A user cmdq could possibly mix different commands in
> a single batch if the driver isn't aware of such an errata. So,
> I think I'd need some twist when the host has a FORCE_SYNC flag
> in my v3.

Just found that you unset the NESTING feature flag in PATCH-4
for this errata too. So, the solution in my v2 should be safe.

Thanks
Nicolin