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Re: [Xen-devel] [PATCH for-4.12] x86/hvm: Fix hvm_cr4_guest_valid_bits() for PVH dom0

On Mon, Jan 28, 2019 at 01:56:29PM +0000, Andrew Cooper wrote:
> Before the cpuid_policy logic came along, %cr4 auditing on migrate-in was
> complicated, because at that point no CPUID information had been set for the
> guest.  Auditing against the host CPUID was better than nothing, but not
> ideal.
> Order of information in the migration stream is still an issue (hence we still
> need to keep the restore parameter to cope with a nested virt corner case),
> but since Xen 4.9, the domain starts with the applicable max policy, which is
> a more appropriate upper bound than the host cpuid policy.
> This also makes the fix from c/s 9d2efbafb8 obsolete, as not even dom0 starts
> without a policy.
> Finally, reposition the UMIP logic as it is the only row out of order.
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

It is indeed the case that all x86 domains will get a cpuid policy,
auditing against that makes more sense. But what about code in
hvm_efer_valid? Why didn't you make it work with arch.cpuid?


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