From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: jasowang@redhat.com, vkuznets@redhat.com, qemu-devel@nongnu.org,
mst@redhat.com
Subject: Re: [PATCH v2 0/3] exclude hyperv synic sections from vhost
Date: Fri, 17 Jan 2020 12:35:04 +0000 [thread overview]
Message-ID: <20200117123504.GF3209@work-vm> (raw)
In-Reply-To: <1bab529a-8655-ee28-f137-0311fb7839ff@redhat.com>
* Paolo Bonzini (pbonzini@redhat.com) wrote:
> On 13/01/20 18:36, Dr. David Alan Gilbert (git) wrote:
> >
> > Hyperv's synic (that we emulate) is a feature that allows the guest
> > to place some magic (4k) pages of RAM anywhere it likes in GPA.
> > This confuses vhost's RAM section merging when these pages
> > land over the top of hugepages.
>
> Can you explain what is the confusion like? The memory API should just
> tell vhost to treat it as three sections (RAM before synIC, synIC
> region, RAM after synIC) and it's not clear to me why postcopy breaks
> either.
See my v3 I posted yesterday; I've made this a lot simpler by just
turning the alignment off for vhost-kernel and only enabling it for
vhost-user; vhost-user skips any section without a backing fd anyway,
so the synic problem goes away, as does another problem reported by
Peter Lieven that he was seeing that seemed like one of the VGA regions
getting in the way (which I'd not seen before).
Dave
> Paolo
>
> > Since they're not normal RAM, and they shouldn't have vhost DMAing
> > into them, exclude them from the vhost set.
>
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
next prev parent reply other threads:[~2020-01-17 12:36 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-13 17:36 [PATCH v2 0/3] exclude hyperv synic sections from vhost Dr. David Alan Gilbert (git)
2020-01-13 17:36 ` [PATCH v2 1/3] vhost: Add names to section rounded warning Dr. David Alan Gilbert (git)
2020-01-13 17:36 ` [PATCH v2 2/3] memory: Allow a MemoryRegion to be marked no_vhost Dr. David Alan Gilbert (git)
2020-01-14 7:19 ` Michael S. Tsirkin
2020-01-14 11:26 ` Dr. David Alan Gilbert
2020-01-14 14:52 ` Michael S. Tsirkin
2020-01-14 15:02 ` Alex Williamson
2020-01-13 17:36 ` [PATCH v2 3/3] hyperv/synic: Mark regions as no vhost Dr. David Alan Gilbert (git)
2020-01-13 18:13 ` [PATCH v2 0/3] exclude hyperv synic sections from vhost Paolo Bonzini
2020-01-13 18:58 ` Dr. David Alan Gilbert
2020-01-14 7:17 ` Michael S. Tsirkin
2020-01-17 12:35 ` Dr. David Alan Gilbert [this message]
2020-01-15 12:12 ` Roman Kagan
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