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Re: [Xen-devel] [Patch v2] x86/boot: Use mov to cr0 in preference to lmsw

  • To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxx>
  • From: Keir Fraser <keir.xen@xxxxxxxxx>
  • Date: Wed, 28 Aug 2013 13:54:50 +0100
  • Cc: Jan Beulich <JBeulich@xxxxxxxx>
  • Delivery-date: Wed, 28 Aug 2013 12:55:25 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xen.org>
  • Thread-index: Ac6j7cgZJJje97SQaEu5xfdu3eMvOw==
  • Thread-topic: [Xen-devel] [Patch v2] x86/boot: Use mov to cr0 in preference to lmsw

On 28/08/2013 11:36, "Andrew Cooper" <andrew.cooper3@xxxxxxxxxx> wrote:

> lmsw is for compability for 286 processors only, and any more modern
> processors are recomended to use mov to cr0.  Xen has never been capable of
> booting on a 286, given its multiboot entry.
> Furthermore, this avoids needless playing with the MP, EM and TS bits.  These
> do get explicitly chosen slightly later on boot.
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> CC: Keir Fraser <keir@xxxxxxx>
> CC: Jan Beulich <JBeulich@xxxxxxxx>

I don't know. This seems quite pointless.

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