Re: port-xen/57199: Pure PVH i386 guests hang on disk activity

[Brad Spencer <brad%anduin.eldar.org@localhost>]

Taylor R Campbell <riastradh%NetBSD.org@localhost> writes:

> The following reply was made to PR kern/57199; it has been noted by GNATS.
>
> From: Taylor R Campbell <riastradh%NetBSD.org@localhost>
> To: Brad Spencer <brad%anduin.eldar.org@localhost>
> Cc: bouyer%antioche.eu.org@localhost, gnats-bugs%NetBSD.org@localhost,
> 	netbsd-bugs%NetBSD.org@localhost, gdt%lexort.com@localhost
> Subject: Re: port-xen/57199: Pure PVH i386 guests hang on disk activity
> Date: Mon, 15 Jul 2024 18:52:14 +0000
>
>  > Date: Mon, 15 Jul 2024 14:31:41 -0400
>  > From: Brad Spencer <brad%anduin.eldar.org@localhost>
>  > 
>  > b) I will test Taylor's patch on the DOMU.  Doing that on the DOM0 is
>  > probably not something I can manage right now.
>  
>  I should clarify: I suspect this may be needed on the dom0, but only
>  if the dom0 _also_ runs uniprocessor, i.e., single-vCPU.
>  
>  If you can run crash(8) or enter ddb on the dom0, you can check like
>  so:
>  
>  # crash
>  Crash version 10.0_STABLE, image version 10.0.
>  WARNING: versions differ, you may not be able to examine this image.
>  Kernel compiled without options LOCKDEBUG.
>  Output from a running system is unreliable.
>  crash> x/i membar_sync,3
>  _membar_enter:  lock addq       $0,fffffffffffffff8 (%rsp)
>  _membar_enter+0x7:      ret
>  _membar_enter+0x8:      nopl
>  
>  If it says `lock addq' or `lock addl', you're good.  If it's just
>  `addq' or `addl' with no `lock', the patch is needed.
>  

The DOM0 is NetBSD_9.x, but it appears to be ok according to what you
wrote above:

DOM0# crash
Crash version 9.3_STABLE, image version 9.3_STABLE.
Output from a running system is unreliable.
crash> x/i membar_sync,3
_membar_sync:   lock addq       $0,fffffffffffffff8 (%rsp)
_membar_sync+0x7:       ret
_membar_sync+0x8:       nopl
crash>