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Re: [PATCH] x86/CPUID: don't shrink hypervisor leaves


  • To: Jan Beulich <jbeulich@xxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
  • From: Roger Pau Monné <roger.pau@xxxxxxxxxx>
  • Date: Mon, 18 Oct 2021 13:45:29 +0200
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  • Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Wei Liu <wl@xxxxxxx>
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  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On Fri, May 07, 2021 at 10:40:34AM +0200, Jan Beulich wrote:
> This is a partial revert of 540d911c2813 ("x86/CPUID: shrink
> max_{,sub}leaf fields according to actual leaf contents"). Andrew points
> out that XXX.
> 
> Reported-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> ---
> Obviously the XXX wants filling in. So far I did not really understand
> what bad consequences there might be, but I can agree with the undoing
> of this part of the original change along the lines of why the Viridian
> side adjustment was also requested to be dropped (before the patch went
> in).

I have to admit I'm confused about this. Here the maximum leaf
reported only changes between PV and HVM, but never as a result of the
features exposed, which I think should be fine?

Ie: I recall the problem being the maximum leaf possibly shrinking
when migrating, but that's not the case.

Thanks, Roger.



 


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