Subject: Re: [PATCH v3 0/3] iommu/arm-smmu-v3: Tegra264 invalidation workaround

From: Jason Gunthorpe <[email-masked]>
Date: Tue, 2 Jun 2026 15:23:15 -0300

On Tue, Jun 02, 2026 at 04:31:29PM +0000, Mostafa Saleh wrote:
> On Mon, Jun 01, 2026 at 10:48:42AM +0000, Ashish Mhetre wrote:
> > Nvidia Tegra264 SMMUs are affected by an erratum where a TLB entry can
> > survive an invalidation that races with concurrent traffic targeting
> > the same entry. The hardware-recommended software workaround is to
> > issue every CFGI/TLBI command (each followed by CMD_SYNC) twice. The
> > second issue must execute only after the first issue's CMD_SYNC has
> > completed, giving the sequence:
> 
> This seems quite intrusive, will the TLB entry survive if you push a
> full invalidation instead?

It's 36 lines and completely contained to the insides of the command
sumbissions code??

Stuff like this is why I was guiding you to use the more code exactly
as is for pkvm. Historically there have been many invalidation related
errata, and invalidate twice seems to be a theme in fixing many of
them.

Jason