Re: [Xen-devel] [PATCH] svm: allow guest to use EFER.FFXSE and EFER.LMSLE

[Keir Fraser <keir@xxxxxxxxxxxxx>]

On 9/8/07 13:08, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote:

> (Applies cleanly only on top of the previously sent SVM/LBR patch.)
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>

I applied the FFXSE parts but not the LMSLE parts. I don't think it's
reasonable to support an undocumented processor feature, and this one is
particularly worrying:
 * We have to enable it inside Xen in order to detect it. But I have no docs
about what effects that has (even though the time it is enabled for is
admittedly very short).
 * Since the only mentions of EFER.LMSLE that I can find are in
family-specific BIOS and kernel developers' guides, I have no idea whether
the flag is architectural and hence whether that bit in EFER will retain its
meaning in future processor families.

 -- Keir


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