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: gnats-bugs%netbsd.org@localhost
Cc: 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 15:00:03 -0400

 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>