Re: [Xen-devel] [PATCH] tools/libxc: Fix the reported max_leaf values for PV guests

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Wed, Jan 11, 2017 at 12:44:41PM +0000, Andrew Cooper wrote:
> When iterating through CPUID leaves to generating a policy, libxc will clip
> itself at the hardcoded maxima, meaning that no data outside of the hardcoded
> maxima are provided to Xen (in turn, causing Xen to return zeros if these
> leaves are requested.)
> 
> The HVM code also clips the max_leaf data reported to the guest, but the PV
> side didn't.
> 
> This results in a PV guest using the emulated CPUID, or via Xen using CPUID
> faulting, to observe a max_leaf higher than the toolstack wants, although with
> zeros being returned in the intervening leaves.
> 
> Fix the PV side to behave like the HVM side, and clip the max_leaf values in
> leaf 0 and 0x80000000.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>

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