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

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Message-ID: <87d603ce-578d-46a7-87b1-54befccc6fad@iscas.ac.cn>
Date: Thu, 9 Oct 2025 13:50:11 +0800
From: Vivian Wang <wangruikang@...as.ac.cn>
To: Greg KH <gregkh@...uxfoundation.org>
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 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,
Vivian "dramforever" Wang

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.

[1]: https://github.com/RVCK-Project/rvck
[2]: https://docs.rockos.dev/