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SubjectRe: [PATCH v2 03/16] KVM: x86: Always use non-compat vcpu_runstate_info size for gfn=>pfn cache
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On 10/27/22 16:44, Sean Christopherson wrote:
>> - long mode cannot be changed after the shared info page is enabled (which
>> makes sense because the shared info page also has a compat version)
>
> How is this not introducing an additional restriction? This seems way more
> onerous than what is effectively a revert.
>
>> - the caches must be activated after the shared info page (which enforces
>> that the vCPU attributes are set after the VM attributes)
>>
>> This is technically a userspace API break, but nobody is really using this
>> API outside Amazon so... Patches coming after I finish testing.
>
> It's not just userspace break, it affects the guest ABI as well.

Yes, I was talking of the VMM here; additional restrictions are fine there.

The guests however should be compatible with Xen, so you also need to
re-activate the cache after the hypercall page is written, but that's
two lines of code.

Paolo

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