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Re: [PATCH 01/12] x86: Reject CPU policies with vendors other than the host's
- To: Alejandro Vallejo <alejandro.garciavallejo@xxxxxxx>
- From: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- Date: Tue, 10 Feb 2026 09:19:24 +0100
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- Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx, Jan Beulich <jbeulich@xxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Jason Andryuk <jason.andryuk@xxxxxxx>
- Delivery-date: Tue, 10 Feb 2026 08:19:44 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On Fri, Feb 06, 2026 at 05:15:23PM +0100, Alejandro Vallejo wrote:
> While in principle it's possible to have a vendor virtualising another,
> this is fairly tricky in practice. Not doing so enables certain
> optimisations with regards to vendor checks in later patches.
>
> Signed-off-by: Alejandro Vallejo <alejandro.garciavallejo@xxxxxxx>
> ---
> Patch 1 from the cross-vendor series. Do not merge here. It's simply for
> consistency.
> ---
> xen/lib/x86/policy.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/xen/lib/x86/policy.c b/xen/lib/x86/policy.c
> index f033d22785..079c42a29b 100644
> --- a/xen/lib/x86/policy.c
> +++ b/xen/lib/x86/policy.c
> @@ -15,7 +15,8 @@ int x86_cpu_policies_are_compatible(const struct cpu_policy
> *host,
> #define FAIL_MSR(m) \
> do { e.msr = (m); goto out; } while ( 0 )
>
> - if ( guest->basic.max_leaf > host->basic.max_leaf )
> + if ( (guest->x86_vendor != host->x86_vendor) ||
> + (guest->basic.max_leaf > host->basic.max_leaf) )
You possibly want to expand test-cpu-policy.c to add a small test to
ensure this works as expected? Not that it shouldn't, but it's
trivial to expand test_is_compatible_{success,failure}() to add a
small test for the vendor checking.
Thanks, Roger.
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