Re: [PATCH] Revert "iommu/arm-smmu: Convert to domain_alloc_paging()"

From: Jason Gunthorpe <jgg@ziepe.ca>
To: Will Deacon <will@kernel.org>
Cc: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
	Robin Murphy <robin.murphy@arm.com>,
	Joerg Roedel <joro@8bytes.org>, Rob Clark <robdclark@gmail.com>,
	linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev,
	linux-arm-msm@vger.kernel.org
Subject: Re: [PATCH] Revert "iommu/arm-smmu: Convert to domain_alloc_paging()"
Date: Tue, 13 Feb 2024 10:42:08 -0400	[thread overview]
Message-ID: <20240213144208.GL765010@ziepe.ca> (raw)
In-Reply-To: <20240213140900.GE28926@willie-the-truck>

On Tue, Feb 13, 2024 at 02:09:00PM +0000, Will Deacon wrote:
> Hey Jason,
> 
> On Tue, Feb 13, 2024 at 09:47:26AM -0400, Jason Gunthorpe wrote:
> > On Tue, Feb 13, 2024 at 12:59:52PM +0000, Will Deacon wrote:
> > > > The typical kernel standard is to fix bugs in patches and only reach
> > > > for a wholesale revert if the community is struggling with bug
> > > > fixing. Dmitry already tested removing that hunk, Robin explained the
> > > > issue, we understand the bug fix is to remove the
> > > > arm_smmu_init_domain_context() call. Nothing justifies a full scale
> > > > revert.
> > > 
> > > I can't say I'm aware of any consensus for how to handle this, to be
> > > completely honest with you. 
> > 
> > Well, I work in a lot of subsystems and this is a surprise to me and
> > not something I've seen before. Fix the bug, move forward. Reverts are
> > a cultural admission of failure. I use threats of a revert as a hammer
> > to encourage people to pay attention to the bugs. I hardly ever
> > actually revert things. What does reverting their code say to my
> > submitters???
> 
> Huh. I guess I'm lucky never to have worked in a environment where that
> is the case. In fact, my experience is quite the opposite: revert first
> so that things get back to a working state and the developer/submitter
> has some breathing room to rework the broken code. It's actually fairly
> blameless if you get it right and when you have a half-functional CI it's
> pretty much a necessity. Anyway, I digress...

Fascinating, I am glad we had this discussion because I was pretty put
off by this talk of revert in this and the other thread. Cultural
differences!

Thanks,
Jason

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