Re: kern/57199 (Pure PVH i386 guests hang on disk activity)

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Tue, Jul 16, 2024 at 11:33:39PM +0000, Taylor R Campbell wrote:
> > Date: Wed, 17 Jul 2024 01:15:12 +0200
> > From: Manuel Bouyer <bouyer%antioche.eu.org@localhost>
> > 
> > On Tue, Jul 16, 2024 at 10:49:32PM +0000, riastradh%NetBSD.org@localhost wrote:
> > > fixed in HEAD, needs pullup-10 and pullup-9
> > 
> > AFAIK it's not needed in netbsd-9, PVH is not supported before -10
> 
> Don't XEN3_DOM0 and XEN3_DOMU kernels have, e.g., xennet(4)?  If they
> rely on xen_mb to enforce store-before-load ordering with respect to
> the hypervisor (possibly on another physical CPU), they may need this
> fix.
> 
> That said, by accident, it looks like this will only be relevant for
> very old 32-bit x86 CPUs -- those without SSE2.  On CPUs with SSE2,
> netbsd-9 hotpatches membar_sync to use MFENCE.  And all amd64 CPUs
> have SSE2.

AFAIK hotpatch is disabled for XEN PV kernels.

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--