On Sat, Nov 13, 2021 at 06:28:16PM +0000, Sean Christopherson wrote:

Another issue is that the host kernel, which despite being "untrusted", absolutely
should be acting in the best interests of the guest.  Allowing userspace to inject
#VC, e.g. to attempt to attack the guest by triggering a spurious PVALIDATE, means
the kernel is failing miserably on that front.

Well, no. The kernel is only a part of the hypervisor, KVM userspace is
another. It is possible today for the userspace part(s) to interact in bad
ways with the guest and trick or kill it. Allowing user-space to cause a
#VC in the guest is no different from that.

Regards,

-- 
Jörg Rödel
jroedel@suse.de

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