Re: [Xen-devel] [PATCH 08/15] x86/hvm: Reposition the modification of raw segment data from the VMCB/VMCS

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Andrew Cooper [mailto:andrew.cooper3@xxxxxxxxxx]
> Sent: Wednesday, November 23, 2016 11:39 PM
> 
> 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.
> 
> 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>

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