Re: [Xen-devel] [PATCH v2 10/19] x86/hvm: Reposition the modification of raw segment data from the VMCB/VMCS

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 11/28/2016 06:13 AM, Andrew Cooper wrote:
> Intel VT-x and AMD SVM provide access to the full segment descriptor cache via
> fields in the VMCB/VMCS.  However, the bits which are actually checked by
> hardware and preserved across vmentry/exit are inconsistent, and the vendor
> accessor functions perform inconsistent modification to the raw values.
>
> Convert {svm,vmx}_{get,set}_segment_register() into raw accessors, and alter
> hvm_{get,set}_segment_register() to cook the values consistently.  This allows
> the common emulation code to better rely on finding architecturally-expected
> values.
>
> While moving the code performing the cooking, fix the %ss.db quirk.  A NULL
> selector is indicated by .p being clear, not the value of the .type field.
>
> This does cause some functional changes because of the modifications being
> applied uniformly.  A side effect of this fixes latent bugs where
> vmx_set_segment_register() didn't correctly fix up .G for segments, and
> inconsistent fixing up of the GDTR/IDTR limits.
>
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>


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