linux-kernel - Re: [PATCH] drm/msm: Wire up tlb ops

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Message-ID: <ZdRfR3xqYIYNISbL@hovoldconsulting.com>
Date: Tue, 20 Feb 2024 09:13:59 +0100
From: Johan Hovold <johan@...nel.org>
To: Rob Clark <robdclark@...il.com>
Cc: dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
	linux-arm-msm@...r.kernel.org, Rob Clark <robdclark@...omium.org>,
	Robin Murphy <robin.murphy@....com>,
	Abhinav Kumar <quic_abhinavk@...cinc.com>,
	Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
	Sean Paul <sean@...rly.run>,
	Marijn Suijten <marijn.suijten@...ainline.org>,
	David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
	Bjorn Andersson <andersson@...nel.org>,
	Jordan Crouse <jordan@...micpenguin.net>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/msm: Wire up tlb ops

On Thu, Feb 15, 2024 at 07:28:53AM -0800, Rob Clark wrote:
> On Wed, Feb 14, 2024 at 11:34 PM Johan Hovold <johan@...nel.org> wrote:
> >
> > On Tue, Feb 13, 2024 at 09:23:40AM -0800, Rob Clark wrote:
> > > From: Rob Clark <robdclark@...omium.org>
> > >
> > > The brute force iommu_flush_iotlb_all() was good enough for unmap, but
> > > in some cases a map operation could require removing a table pte entry
> > > to replace with a block entry.  This also requires tlb invalidation.
> > > Missing this was resulting an obscure iova fault on what should be a
> > > valid buffer address.
> > >
> > > Thanks to Robin Murphy for helping me understand the cause of the fault.
> > >
> > > Cc: Robin Murphy <robin.murphy@....com>
> > > Fixes: b145c6e65eb0 ("drm/msm: Add support to create a local pagetable")
> >
> > Sounds like you're missing a
> >
> > Cc: stable@...r.kernel.org
> >
> > here? Or is there some reason not to backport this fix (to 5.9 and later
> > kernels)?
> 
> No reason, I just expected the Fixes tag was sufficient

No, you should still mark patches intended for stable with an explicit
CC-stable tag (as per the documentation).

The fact that Sasha and his AI tries to catch fixes which the author and
maintainer failed to tag as a fallback should not be relied upon. It
also makes it harder for the stable team and others to determine what
the intention with a fix was.

Johan