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Re: [PATCH 6/7] x86/cpuid: Fix handling of XSAVE dynamic leaves


  • To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Thu, 23 May 2024 18:16:56 +0200
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  • Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • Delivery-date: Thu, 23 May 2024 16:17:04 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 23.05.2024 13:16, Andrew Cooper wrote:
> First, if XSAVE is available in hardware but not visible to the guest, the
> dynamic leaves shouldn't be filled in.
> 
> Second, the comment concerning XSS state is wrong.  VT-x doesn't manage
> host/guest state automatically, but there is provision for "host only" bits to
> be set, so the implications are still accurate.
> 
> Introduce xstate_compressed_size() to mirror the uncompressed one.  Cross
> check it at boot.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
Irrespective ...

> v3:
>  * Adjust commit message about !XSAVE guests
>  * Rebase over boot time cross check
>  * Use raw policy

... it should probably have occurred to me earlier on to ask: Why raw policy?
Isn't the host one the more appropriate one to use for any kind of internal
decisions?

Jan



 


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