From: Andrew Cooper <andrew.cooper3@citrix.com>
To: George Dunlap <george.dunlap@citrix.com>,
Anthony PERARD <anthony.perard@citrix.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>,
"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>
Subject: Re: OVMF very slow on AMD
Date: Thu, 28 Jul 2016 11:54:27 +0100 [thread overview]
Message-ID: <457e48f9-9116-8c86-02c4-ac9fd9d274a1@citrix.com> (raw)
In-Reply-To: <CAFLBxZY3bVwNr6Woi9nnsk-jG8wH5RFChcTfqQiGttsOKh6dMg@mail.gmail.com>
On 28/07/16 11:43, George Dunlap wrote:
> On Thu, Jul 28, 2016 at 11:18 AM, Anthony PERARD
> <anthony.perard@citrix.com> wrote:
>> On Wed, Jul 27, 2016 at 03:45:23PM -0400, Boris Ostrovsky wrote:
>>> On 07/27/2016 07:35 AM, Anthony PERARD wrote:
>>>> On Wed, Jul 27, 2016 at 12:08:04PM +0100, Anthony PERARD wrote:
>>>>> I can try to describe how OVMF is setting up the memory.
>>>> From the start of the day:
>>>> setup gdt
>>>> cr0 = 0x40000023
>>> I think this is slightly odd, with bit 30 (cache disable) set. I'd
>>> suspect that this would affect both Intel and AMD though.
>>>
>>> Can you try clearing this bit?
>> That works...
>>
>> I wonder why it does not appear to affect Intel or KVM.
> Are those bits hard-coded, or are they set based on the hardware
> that's available?
>
> Is it possible that the particular combination of CPUID bits presented
> by Xen on AMD are causing a different value to be written?
>
> Or is it possible that the cache disable bit is being ignored (by Xen)
> on Intel and KVM?
If a guest has no hardware, then it has no reason to actually disable
caches. We should have logic to catch this an avoid actually disabling
caches when the guest asks for it.
~Andrew
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel
next prev parent reply other threads:[~2016-07-28 10:54 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 [this message]
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
2016-07-18 14:10 ` Anthony PERARD
2016-07-18 15:09 ` Anthony PERARD
2016-07-22 10:40 ` Dario Faggioli
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=457e48f9-9116-8c86-02c4-ac9fd9d274a1@citrix.com \
--to=andrew.cooper3@citrix.com \
--cc=anthony.perard@citrix.com \
--cc=boris.ostrovsky@oracle.com \
--cc=george.dunlap@citrix.com \
--cc=xen-devel@lists.xen.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).