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Re: [PATCH 8/8] x86/cpuid: Move VMX/SVM out of the default policy

  • To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
  • From: Roger Pau Monné <roger.pau@xxxxxxxxxx>
  • Date: Thu, 1 Oct 2020 13:04:59 +0200
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  • Cc: Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxx>, Wei Liu <wl@xxxxxxx>
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On Wed, Sep 30, 2020 at 02:42:48PM +0100, Andrew Cooper wrote:
> Nested virt is still experimental, and requires explicitly opting in to at
> domain create time.  The VMX/SVM features should not be visible by default.
> Also correct them from all HVM guests, to just HAP-enabled guests.  This has
> been the restriction for SVM right from the outset (c/s e006a0e0aaa), while
> VMX was first introduced supporting shadow mode (c/s 9122c69c8d3) but later
> adjusted to HAP-only (c/s 77751ed79e3).
> There is deliberately no adjustment to xc_cpuid_apply_policy() for pre-4.14
> migration compatibility.  The migration stream doesn't contain the required
> architectural state for either VMX/SVM, and a nested virt VM which migrates
> will explode in weird and wonderful ways.
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Acked-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

Thanks, Roger.



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