From: Anthony PERARD <anthony.perard@citrix.com>
To: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
George Dunlap <george.dunlap@citrix.com>,
"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>
Subject: Re: OVMF very slow on AMD
Date: Fri, 29 Jul 2016 16:54:42 +0100 [thread overview]
Message-ID: <20160729155442.GS1835@perard.uk.xensource.com> (raw)
In-Reply-To: <3d3c1358-6f3b-157a-b09d-836331e67336@oracle.com>
On Thu, Jul 28, 2016 at 03:54:34PM -0400, Boris Ostrovsky wrote:
> On 07/28/2016 03:44 PM, Andrew Cooper wrote:
> >>>> As far as Intel vs AMD implementation in Xen, we have vmx_handle_cd()
> >>>> but no corresponding SVM code. Could it be that we need to set gPAT, for
> >>>> example?
> >>> A better approach would be to find out why ovmf insists on disabling
> >>> caches at all. Even if we optimise the non-PCI-device case in the
> >>> hypervisor, a passthrough case will still run like treacle if caches are
> >>> disabled.
> >> True, we should understand why OVMF does this. But I think we also need
> >> to understand what makes Intel run faster. Or is it already clear from
> >> vmx_handle_cd()?
> > Wow this code is hard to follow :(
> >
> > handle_cd() is only called when an IOMMU is enabled and the domain in
> > question has access to real ioports or PCI devices.
> >
> > However, I really can't spot anything that ends up eliding the
> > cache-disable setting even for Intel. This clearly needs further
> > investigation.
>
> So as an easy start perhaps Anthony could check whether this call is
> made with his guest running on Intel.
No, handle_cd is never called on my guest.
--
Anthony PERARD
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next prev parent reply other threads:[~2016-07-29 15:54 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-14 15:53 OVMF very slow on AMD Anthony PERARD
2016-07-15 13:48 ` Konrad Rzeszutek Wilk
2016-07-15 15:22 ` Boris Ostrovsky
2016-07-27 11:08 ` Anthony PERARD
2016-07-27 11:35 ` Anthony PERARD
2016-07-27 19:45 ` Boris Ostrovsky
2016-07-28 10:18 ` Anthony PERARD
2016-07-28 10:43 ` George Dunlap
2016-07-28 10:54 ` Andrew Cooper
2016-07-28 11:28 ` Anthony PERARD
2016-07-28 15:17 ` Boris Ostrovsky
2016-07-28 15:51 ` Andrew Cooper
2016-07-28 19:25 ` Boris Ostrovsky
2016-07-28 19:44 ` Andrew Cooper
2016-07-28 19:54 ` Boris Ostrovsky
2016-07-29 15:54 ` Anthony PERARD [this message]
2016-07-18 14:10 ` Anthony PERARD
2016-07-18 15:09 ` Anthony PERARD
2016-07-22 10:40 ` Dario Faggioli
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