Re: regression: SCSI/SATA failure

[Artem Bityutskiy <dedekind1@gmail.com>]

Linux-Regression-ID: lr#15a115

On Thu, 2018-02-22 at 16:54 +0200, Artem Bityutskiy wrote:
> Hi Christoph,
> 
> one of our test box Skylake servers does not boot with v4.16-rcX.
> Bisection lead us to this commit:
> 
> 84676c1f21e8 genirq/affinity: assign vectors to all possible CPUs
> 
> Reverting this single commit fixes the problem.
> 
> The server is a Dell R640 machine with the latest Dell BIOS. It has a
> single SATA SSD and we do not use raid, even though the system does
> have a megaraid controller.

Correction: we have Raid0 with this single disk.

> Are you aware of this issue? Below is the failure message and the
> full
> dmesg with some debugging boot parameters is here:
> 
> https://pastebin.com/raw/tTYrTAEQ

FYI, the regression still exists and reverting this single patch fixes
it. But today Dell server

I did not have time to really debug this, but I think people who are
working with this should quickly see what is going on.

I think the platform reports way too large possible CPU count. Indeed,
in dmesg I see this:

[    0.000000] smpboot: Allowing 328 CPUs, 224 hotplug CPUs

224 is way too large for this system. It only has 2 sockets, it but the
number looks like if the system had 4 sockets.

The commit changes IRQ affinity logic from being per-present CPU to
being per-possible CPU:

-       for_each_present_cpu(cpu)
+       for_each_possible_cpu(cpu)

And it looks like this has an unexpected side-effect on this Dell
platform.

Artem.