From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>,
George Dunlap <george.dunlap@citrix.com>,
Anthony PERARD <anthony.perard@citrix.com>
Cc: "xen-devel@lists.xen.org" <xen-devel@lists.xen.org>
Subject: Re: OVMF very slow on AMD
Date: Thu, 28 Jul 2016 15:54:34 -0400 [thread overview]
Message-ID: <3d3c1358-6f3b-157a-b09d-836331e67336@oracle.com> (raw)
In-Reply-To: <97ba5ce9-226f-71e7-3d5f-3be225fce631@citrix.com>
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.
-boris
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next prev parent reply other threads:[~2016-07-28 19:54 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 [this message]
2016-07-29 15:54 ` Anthony PERARD
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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