Re: [Xen-devel] [PATCH v2 2/2] nvmx: always trap accesses to x2APIC MSRs

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Roger Pau Monne <roger.pau@xxxxxxxxxx>
> Sent: Wednesday, January 29, 2020 10:45 PM
> 
> Nested VMX doesn't expose support for
> SECONDARY_EXEC_VIRTUALIZE_X2APIC_MODE,
> SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY or
> SECONDARY_EXEC_APIC_REGISTER_VIRT, and hence the x2APIC MSRs should
> always be trapped in the nested guest MSR bitmap, or else a nested
> guest could access the hardware x2APIC MSRs given certain conditions.
> 
> Accessing the hardware MSRs could be achieved by forcing the L0 Xen to
> use SECONDARY_EXEC_VIRTUALIZE_X2APIC_MODE and
> SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY or
> SECONDARY_EXEC_APIC_REGISTER_VIRT (if supported), and then creating a
> L2 guest with a MSR bitmap that doesn't trap accesses to the x2APIC
> MSR range. Then OR'ing both L0 and L1 MSR bitmaps would result in a
> bitmap that doesn't trap certain x2APIC MSRs and a VMCS that doesn't
> have SECONDARY_EXEC_VIRTUALIZE_X2APIC_MODE and
> SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY or
> SECONDARY_EXEC_APIC_REGISTER_VIRT set either.
> 
> Fix this by making sure x2APIC MSRs are always trapped in the nested
> MSR bitmap.
> 
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel