linux-kernel - Re: [PATCH v2] cpu: mark cpu_possible_mask as __ro_after

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Date: Wed, 3 Apr 2024 14:43:37 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Guenter Roeck <linux@...ck-us.net>
CC: Alexey Dobriyan <adobriyan@...il.com>, Thomas Gleixner
	<tglx@...utronix.de>, Peter Zijlstra <peterz@...radead.org>,
	<linux-kernel@...r.kernel.org>, <linuxarm@...wei.com>
Subject: Re: [PATCH v2] cpu: mark cpu_possible_mask as __ro_after_init

On Wed, 27 Mar 2024 11:36:28 -0700
Guenter Roeck <linux@...ck-us.net> wrote:

> On Wed, Mar 27, 2024 at 06:10:53PM +0000, Jonathan Cameron wrote:
> > On Thu, 22 Feb 2024 14:19:35 +0300
> > Alexey Dobriyan <adobriyan@...il.com> wrote:
> >   
> > > cpu_possible_mask is by definition "cpus which could be hotplugged without
> > > reboot". It's a property which is fixed after kernel enumerates hardware
> > > configuration.
> > > 
> > > Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>  
> > 
> > Causes a crash in this path (via CPU HP testing on qemu)
> > Pretending to be an AMD Genoa, but I doubt that matters.
> >   
> 
> Can you send me the configuration, qemu command line, and commands
> executed ? I'd like to add that to my test setup if possible.
> 
> Thanks,
> Guenter

Hi Guenter,

Great to get some regular tests running on this.

I haven't minimized this that much, so probably don't need most of this
setup.

qemu-system-x86_64 -M q35,cxl=on,sata=off,smbus=off
 -m 12g -cpu EPYC-Genoa -smp 2,maxcpus=4,sockets=2 \
 -kernel bzImage \
 -drive if=none,file=/mnt/d/images-x86/full2.qcow2,format=qcow2,id=hd \
 -device ioh3420,id=root_port1 \
 -device nvme,serial=deadbeef,drive=hd \
 -nographic -no-reboot -append 'earlycon console=ttyS0 root=/dev/nvme0n1p3 fsck.mode=skip tp_printk maxcpus=4' \
 -monitor telnet:127.0.0.1:1235,server,nowait \
 -object memory-backend-ram,size=12G,id=mem0 \
 -numa node,nodeid=0,memdev=mem0 \
 -numa node,nodeid=1 \
 -numa cpu,node-id=0,socket-id=0 \
 -numa cpu,node-id=0,socket-id=0 \
 -numa cpu,node-id=1,socket-id=1 \
 -numa cpu,node-id=1,socket-id=1

telnet 1235
(qemu) device_add EPYC-Genoa-x86_64-cpu,node-id=1,socket-id=1,core-id=0,thread-id=0 

Jonathan