Re: [PATCH v3 1/2] hw/nvme: Implement shadow doorbell buffer support

[Guenter Roeck <linux@roeck-us.net>]

On Thu, Dec 08, 2022 at 12:13:55PM -0800, Guenter Roeck wrote:
> On Thu, Dec 08, 2022 at 10:47:42AM -0800, Guenter Roeck wrote:
> > > 
> > > A cq head doorbell mmio is skipped... And it is not the fault of the
> > > kernel. The kernel is in it's good right to skip the mmio since the cq
> > > eventidx is not properly updated.
> > > 
> > > Adding that and it boots properly on riscv. But I'm perplexed as to why
> > > this didnt show up on our regularly tested platforms.
> > > 
> > > Gonna try to get this in for 7.2!
> > 
> > I see another problem with sparc64.
> > 
> > [    5.261508] could not locate request for tag 0x0
> > [    5.261711] nvme nvme0: invalid id 0 completed on queue 1
> > 
> > That is seen repeatedly until the request times out. I'll test with
> > your patch to see if it resolves this problem as well, and will bisect
> > otherwise.
> > 
> The second problem is unrelated to the doorbell problem.
> It is first seen in qemu v7.1. I'll try to bisect.
> 

Unfortunately, the problem observed with sparc64 also bisects to this
patch. Making things worse, "hw/nvme: fix missing cq eventidx update"
does not fix it (which is why I initially thought it was unrelated).

I used the following qemu command line.

qemu-system-sparc64 -M sun4v -cpu "TI UltraSparc IIi" -m 512 -snapshot \
    -device nvme,serial=foo,drive=d0,bus=pciB \
    -drive file=rootfs.ext2,if=none,format=raw,id=d0 \
    -kernel arch/sparc/boot/image -no-reboot \
    -append "root=/dev/nvme0n1 console=ttyS0" \
    -nographic -monitor none

Guenter