On Thu, Oct 29, 2020 at 4:01 AM Greg KH gregkh@linuxfoundation.org wrote:

On Mon, Oct 26, 2020 at 06:17:00PM -0700, Jian Cai wrote:

...

Hello,

I am working on assembling kernel 5.4 with LLVM's integrated assembler on ChromeOS, and the following patch is required to make it work. Would you please consider backporting it to 5.4?

commit 44623b2818f4a442726639572f44fd9b6d0ef68c Author: Arnd Bergmann arnd@arndb.de Date: Wed May 27 16:17:40 2020 +0200

crypto: x86/crc32c - fix building with clang ias

Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...

It does not apply cleanly, can you please provide a properly backported and tested version?

Hi Jian, Thanks for proactively identifying and requesting a backport of 44623b2818. We'll need it for Android as well soon.

One thing I do when requesting backports from stable is I checkout the branch of the stable tree and see if the patch cherry picks cleanly.

stable is its own tree; you could add it as a remote or check out a copy of it. If you go to kernel.org, click any stable branch, go to summary tab in top left, scroll down for the git url to clone. Then you can `git checkout -b linux-5.4.y origin/linux-5.4.y` to setup the branch. Fetch/pull so it's up to date, then `git cherry-pick -x <sha>`. If it applies without conflict, you can simply send an email as you've done.

If it does not, then you should fix up the conflict, and test it. Then you add your signed off by tag (`git commit --amend -s`) and sometime people leave a note like `[<initials>: had to drop a hunk because a packport of <upstream sha> doesn't exist in this branch]`. If you `git log` in a stable tree's branch, you should be able to see examples.

Another thing I like to do is include comments (in the request email, not the commit message of the patch) on my risk assessment and what the first version of the mainline tree the patch landed in. In a mainline tree (not stable tree), I run this function I've added to my shell's rc file: first_tag () { tag=$1 git describe --match 'v*' --contains "$tag" | sed 's/~.*//' }

$ first_tag <sha> That information can help the stable maintainers better assess the risks in accepting the backport. Though I'm not always great about sticking to my own advice in this regard; the last request I made I forgot to include info about the upstream version. But https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html doesn't mention that's actually necessary.

Anyways I'm sure you already knew most of the above; I don't mean to patronize. My apologies in that regard. Having it typed out helps me forward a URL to future travelers.