Re: [PATCH] KVM: VMX: Forbid userspace MSR filters for x2APIC

[Paolo Bonzini]

On 20/10/20 11:48, Alexander Graf wrote:
> 
>     count: 1,
>     default_allow: false,
>     ranges: [
>         {
>             flags: KVM_MSR_FILTER_READ,
>             nmsrs: 1,
>             base: MSR_EFER,
>             bitmap: { 1 },
>         },
>     ],
> }
> 
> That filter would set all x2apic registers to "deny", but would not be
> caught by the code above. Conversely, a range that explicitly allows
> x2apic ranges with default_allow=0 would be rejected by this patch.

Yes, but the idea is that x2apic registers are always allowed, even
overriding default_allow, and therefore it makes no sense to have them
in a range.  The patch is only making things fail early for userspace,
the policy is defined by Sean's patch.

Paolo