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

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

The following reply was made to PR kern/57199; it has been noted by GNATS.

From: Brad Spencer <brad%anduin.eldar.org@localhost>
To: Manuel Bouyer <bouyer%antioche.eu.org@localhost>
Cc: gnats-bugs%netbsd.org@localhost, kern-bug-people%netbsd.org@localhost, gnats-admin%netbsd.org@localhost,
        netbsd-bugs%netbsd.org@localhost
Subject: Re: port-xen/57199: Pure PVH i386 guests hang on disk activity
Date: Mon, 15 Jul 2024 15:54:54 -0400

 Manuel Bouyer <bouyer%antioche.eu.org@localhost> writes:
 
 > On Mon, Jul 15, 2024 at 03:00:03PM -0400, Brad Spencer wrote:
 >> 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> 
 >
 > Yes, I don't think hotpatch is run when running PV
 
 That may explain something that was strange to me in that the 32-bit
 test system when it was a PV+PVSHIM didn't hang.
 
 
 
 -- 
 Brad Spencer - brad%anduin.eldar.org@localhost - KC8VKS - http://anduin.eldar.org