linux-kernel - Re: [PATCH 6.6.y 0/2] riscv: mm: Backport of mmap hint address fixes

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Message-ID: <2025100931-carefully-exerciser-5d26@gregkh>
Date: Thu, 9 Oct 2025 15:31:17 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: Vivian Wang <wangruikang@...as.ac.cn>
Cc: Albert Ou <aou@...s.berkeley.edu>, Inochi Amaoto <inochiama@...il.com>,
	Han Gao <rabenda.cn@...il.com>,
	Charlie Jenkins <charlie@...osinc.com>,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	Meng Zhuo <mengzhuo@...as.ac.cn>, Yangyu Chen <cyy@...self.name>,
	Palmer Dabbelt <palmer@...belt.com>,
	Palmer Dabbelt <palmer@...osinc.com>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Guo Ren <guoren@...nel.org>, Paul Walmsley <pjw@...nel.org>,
	linux-riscv@...ts.infradead.org, Yao Zi <ziyao@...root.org>
Subject: Re: [PATCH 6.6.y 0/2] riscv: mm: Backport of mmap hint address fixes

On Thu, Oct 09, 2025 at 01:50:11PM +0800, Vivian Wang wrote:
> 
> On 10/9/25 13:00, Greg KH wrote:
> > On Thu, Oct 09, 2025 at 12:19:46PM +0800, Vivian Wang wrote:
> >> [...]
> > Ok, that makes a bit more sense, but again, why is this just showing up
> > now?  What changed to cause this to be noticed at and needed to be fixed
> > at this moment in time and not before?
> 
> As of why this came quite late in the lifetime of the 6.6.y branch, I
> believe it's a combination of two factors.
> 
> Firstly, actual Sv48-capable RISC-V hardware came fairly late. Milk-V
> Megrez (with Eswin EIC7700X), on which the Go TSAN thing ran, was
> shipped only early this year. The DC ROMA II laptop (EIC7702X) and
> Framework mainboard with the same SoC has not even shipped yet, or maybe
> only shipped to developers - I'm not so certain. Most other RISC-V
> machines only have Sv39.
> 
> Secondly, there is interest among some Chinese software vendors to ship
> Linux distros based on a 6.6.y LTS kernel. The "RISC-V Common Kernel"
> (RVCK) project [1], with support from openEuler and various HW vendors,
> maintains backports on top of a 6.6.y kernel. "RockOS" [2] is a distro
> maintained by PLCT Lab, ISCAS, for EIC770{0,2}X-based boards, and it has
> a 6.6.y kernel branch. Both have cherry-picked the mmap patches for now.
> 
> We operate with the understanding that the official stable kernel will
> not be accepting new major features and drivers, but fixes do belong in
> stable, and at least from the perspective of PLCT Lab we generally try
> to send patches instead of hoarding them. Hence, the earlier backport
> request and this backport series.
> 
> I hope this explanation is acceptable.

Thanks for the detailed explaination.  I've queued these up now.

But wow, shipping new products on a 2 year old kernel feels very risky
to me, but hey, what do I know?  :)

> PS: This 6.6 kernel thing isn't just a RISC-V thing, by the way. KylinOS
> V11 has shipped in August with a 6.6 kernel. Deepin and UOS will be
> shipping with 6.6, with UOS "25" shipping maybe late this year or early
> 2026.

That too is crazy.  They should know better.

Just to give a bit of context for this, for the latest 6.6.y release,
6.6.110, there are currently over 300 documented unfixed CVE items in
that branch.  Feels rough to be doing a new release based on that...

good luck!

greg k-h