linux-kernel - Re: [PATCH v2] RISC-V: fix Andes errata build issues

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Date: Wed, 15 May 2024 19:21:16 +0100
From: Conor Dooley <conor@...nel.org>
To: Charlie Jenkins <charlie@...osinc.com>
CC: linux-riscv@...ts.infradead.org, Conor Dooley <conor.dooley@...rochip.com>,
 Paul Walmsley <paul.walmsley@...ive.com>,
 Palmer Dabbelt <palmer@...belt.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] RISC-V: fix Andes errata build issues



On 15 May 2024 18:47:23 IST, Charlie Jenkins <charlie@...osinc.com> wrote:
>On Wed, May 15, 2024 at 06:30:36PM +0100, Conor Dooley wrote:
>> On Wed, May 15, 2024 at 10:18:43AM -0700, Charlie Jenkins wrote:
>> > On Wed, May 15, 2024 at 05:56:30PM +0100, Conor Dooley wrote:
>> > > On Wed, May 15, 2024 at 09:49:24AM -0700, Charlie Jenkins wrote:
>> > > > On Wed, May 15, 2024 at 05:09:34PM +0100, Conor Dooley wrote:
>> > > > > From: Conor Dooley <conor.dooley@...rochip.com>
>> > > > > 
>> > > > > Commit e47c37c24024 ("riscv: Introduce vendor variants of extension
>> > > > > helpers") added includes for the new vendor_extensions.h header in
>> > > > > the T-Head and SiFive errata handling code but didn't do so for Andes,
>> > > > > resulting in allmodconfig build issues when commit 589e2fc85850
>> > > > > ("riscv: Convert xandespmu to use the vendor extension framework")
>> > > > > added a user of a macro defined there.
>> > > > > 
>> > > > > Fixes: 589e2fc85850 ("riscv: Convert xandespmu to use the vendor extension framework")
>> > > > > Signed-off-by: Conor Dooley <conor.dooley@...rochip.com>
>> > > 
>> > > > 
>> > > > I was going to fix this in my next version but was waiting for the
>> > > > reviews on the thead stuff. I wasn't anticipating these patches to be
>> > > > able to jump the queue :)
>> > > 
>> > > Yah, the reason for that is I asked him to take the non-vector parts of
>> > > the series as 6.10 material so that we'd have less stuff movin' around
>> > > in cpufeatures.c so that Clement's Zc* + validation changes wouldn't run
>> > > into a bunch of conflicts etc. Same reason that I pushed for getting
>> > > Andy's vector subset stuff merged today, but that mighta been before you
>> > > hopped in.
>> > > 
>> > > Cheers,
>> > > Conor.
>> > 
>> > Yes I was a couple minutes late to the meeting, whoops.
>> 
>> 
>> It's prob at like 0600 for you, so w/e.
>> 
>> > The subset of
>> > patches that was pulled into for-next is odd to me because there is some
>> > of the thead enablement code as part of the vendor extension enablement
>> > so that there was a user for it. Since the subset on Palmer's for-next
>> > does not have the rest of the thead code there is only a
>> > half-implementation of the thead code, it allows the kernel to probe for
>> > xtheadvector but it doesn't probe anywhere.
>> 
>> I dunno, I think that reporting that the extension is there constitutes a
>> user, it's not gonna be dead code. There's plenty of extensions for
>> which all we do is detect them and nothing more.
>> 
>> > In my opinion, a better solution would be for me to get rid of the thead
>> > code entirely from those patches. So that there is still a user, I can
>> > replace the thead code with the andes versions.
>> 
>> The Andes stuff is in the subset he applied though, so...
>> > 
>> > Since Palmer already pulled in those changes maybe it's too late. There
>> > is not a critical problem here, but it seems like it's bad practice to
>> > introduce code without a user.
>> 
>> ...there is actually a "real" user in xandespmu. I did miss that
>
>I meant there is no user of the xtheadvector addition.
>
>> "riscv: Extend cpufeature.c to detect vendor extensions" actually
>> contained the xtheadvector detection though, rather than just the
>> infrastructure. I think it is probably harmless to have it, but
>> shouldn't be too hard to quickly drop the thead bits either I suppose
>> if you're worried about it.
>
>And the adding vlenb to the DT patches is unrelated to the subset of the
>series that was pulled into Palmer's for-next so spinning that off into
>a different series would be more logical. This is kind of a pointless
>rabbit hole I am getting into, but when we start splitting up series
>the code contained in the patches start to diverge from the cover
>letters that end up in the merge commits.

 The vlenb stuff is also one of the things that I want, it's useful for the validation stuff that Clement is adding.