Dear Greg,


Commit ef86f3a7 (genirq/affinity: assign vectors to all possible CPUs) added
for Linux 4.14.56 causes the aacraid module to not detect the attached devices
anymore on a Dell PowerEdge R720 with two six core 24x E5-2630 @ 2.30GHz.

```
$ dmesg | grep raid
[    0.269768] raid6: sse2x1   gen()  7179 MB/s
[    0.290069] raid6: sse2x1   xor()  5636 MB/s
[    0.311068] raid6: sse2x2   gen()  9160 MB/s
[    0.332076] raid6: sse2x2   xor()  6375 MB/s
[    0.353075] raid6: sse2x4   gen() 11164 MB/s
[    0.374064] raid6: sse2x4   xor()  7429 MB/s
[    0.379001] raid6: using algorithm sse2x4 gen() 11164 MB/s
[    0.386001] raid6: .... xor() 7429 MB/s, rmw enabled
[    0.391008] raid6: using ssse3x2 recovery algorithm
[    3.559682] megaraid cmm: 2.20.2.7 (Release Date: Sun Jul 16 00:01:03 EST 2006)
[    3.570061] megaraid: 2.20.5.1 (Release Date: Thu Nov 16 15:32:35 EST 2006)
[   10.725767] Adaptec aacraid driver 1.2.1[50834]-custom
[   10.731724] aacraid 0000:04:00.0: can't disable ASPM; OS doesn't have ASPM control
[   10.743295] aacraid: Comm Interface type3 enabled
$ lspci -nn | grep Adaptec
04:00.0 Serial Attached SCSI controller [0107]: Adaptec Series 8 12G SAS/PCIe 3 [9005:028d] (rev 01)
42:00.0 Serial Attached SCSI controller [0107]: Adaptec Smart Storage PQI 12G SAS/PCIe 3 [9005:028f] (rev 01)
```

But, it still works with a Dell PowerEdge R715 with two eight core AMD
Opteron 6136, the card below.

```
$ lspci -nn | grep Adaptec
22:00.0 Serial Attached SCSI controller [0107]: Adaptec Series 8 12G SAS/PCIe 3 [9005:028d] (rev 01)
```

Reverting the commit fixes the issue.

commit ef86f3a72adb8a7931f67335560740a7ad696d1d
Author: Christoph Hellwig <hch@lst.de>
Date:   Fri Jan 12 10:53:05 2018 +0800

    genirq/affinity: assign vectors to all possible CPUs
    
    commit 84676c1f21e8ff54befe985f4f14dc1edc10046b upstream.
    
    Currently we assign managed interrupt vectors to all present CPUs.  This
    works fine for systems were we only online/offline CPUs.  But in case of
    systems that support physical CPU hotplug (or the virtualized version of
    it) this means the additional CPUs covered for in the ACPI tables or on
    the command line are not catered for.  To fix this we'd either need to
    introduce new hotplug CPU states just for this case, or we can start
    assining vectors to possible but not present CPUs.
    
    Reported-by: Christian Borntraeger <borntraeger@de.ibm.com>
    Tested-by: Christian Borntraeger <borntraeger@de.ibm.com>
    Tested-by: Stefan Haberland <sth@linux.vnet.ibm.com>
    Fixes: 4b855ad37194 ("blk-mq: Create hctx for each present CPU")
    Cc: linux-kernel@vger.kernel.org
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Signed-off-by: Christoph Hellwig <hch@lst.de>
    Signed-off-by: Jens Axboe <axboe@kernel.dk>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

The problem doesn’t happen with Linux 4.17.11, so there are commits in
Linux master fixing this. Unfortunately, my attempts to find out failed.

I was able to cherry-pick the three commits below on top of 4.14.62,
but the problem persists.

6aba81b5a2f5 genirq/affinity: Don't return with empty affinity masks on error
355d7ecdea35 scsi: hpsa: fix selection of reply queue
e944e9615741 scsi: virtio_scsi: fix IO hang caused by automatic irq vector affinity

Trying to cherry-pick the commits below, referencing the commit
in question, gave conflicts.

1. adbe552349f2 scsi: megaraid_sas: fix selection of reply queue
2. d3056812e7df genirq/affinity: Spread irq vectors among present CPUs as far as possible

To avoid further trial and error with the server with a slow firmware,
do you know what commits should fix the issue?


Kind regards,

Paul


PS: I couldn’t find, who suggested this for stable, that means how
it was picked to be added to stable. Is there an easy way to find
that out?