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Sender: Guenter Roeck <groeck7@gmail.com>
Date:   Wed, 22 Mar 2023 06:24:56 -0700
From:   Guenter Roeck <linux@roeck-us.net>
To:     Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, patches@lists.linux.dev,
        linux-kernel@vger.kernel.org, torvalds@linux-foundation.org,
        akpm@linux-foundation.org, shuah@kernel.org, patches@kernelci.org,
        lkft-triage@lists.linaro.org, pavel@denx.de, jonathanh@nvidia.com,
        f.fainelli@gmail.com, srw@sladewatkins.net, rwarsow@gmx.de
Subject: Re: [PATCH 4.19 00/27] 4.19.278-rc3 review
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On Fri, Mar 17, 2023 at 01:21:03PM +0000, Sudip Mukherjee wrote:
> Hi Greg,
> 
> On Fri, 17 Mar 2023 at 12:55, Greg Kroah-Hartman
> <gregkh@linuxfoundation.org> wrote:
> >
> > On Fri, Mar 17, 2023 at 10:23:42AM +0000, Sudip Mukherjee wrote:
> > > Hi Greg,
> > >
> > > On Thu, Mar 16, 2023 at 10:42:14AM +0100, Greg Kroah-Hartman wrote:
> > > > This is the start of the stable review cycle for the 4.19.278 release.
> > > > There are 27 patches in this series, all will be posted as a response
> > > > to this one.  If anyone has any issues with these being applied, please
> > > > let me know.
> > > >
> > > > Responses should be made by Sat, 18 Mar 2023 09:41:20 +0000.
> > > > Anything received after that time might be too late.
> > >
> > > Build test (gcc version 11.3.1 20230311):
> > > mips: 63 configs -> no  failure
> > > arm: 115 configs -> no failure
> > > arm64: 2 configs -> no failure
> > > x86_64: 4 configs -> no failure
> > > alpha allmodconfig -> no failure
> > > powerpc allmodconfig -> no failure
> > > riscv allmodconfig -> no failure
> > > s390 allmodconfig -> no failure
> > > xtensa allmodconfig -> no failure
> > >
> > > Boot test:
> > > x86_64: Booted on qemu. No regression. [1]
> > >
> > > Boot Regression on test laptop:
> > > Only black screen but ssh worked, so from the dmesg it seems i915 failed.
> >
> > Can you bisect this?
> 
> There was no need to bisect. Only one i915 related commit was there
> and reverting that has fixed it for me.
> 
> 9a0789a26289 ("drm/i915: Don't use BAR mappings for ring buffers with LLC")
> commit 85636167e3206c3fbd52254fc432991cc4e90194 upstream.
> 

Unfortunately, the bad patch made it into v4.19.278 anyway, breaking that
release for all affected users (i915 with LLC support). That has been fixed
in v4.19.279, but it is still unfortunate that the patch made it into the
release even though it was reported that it is problematic.

I don't know what went wrong here, but it would be great if that kind of
problem could be avoided in the future.

Guenter