Re: [Xen-devel] [PATCH v9 3/3] tools/libxc: use superpages during restore of HVM guest

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 06/09/17 13:17, Olaf Hering wrote:
> On Wed, Sep 06, Andrew Cooper wrote:
>
>> On 01/09/17 17:08, Olaf Hering wrote:
>>> +    /* No superpage in 1st 2MB due to VGA hole */
>>> +    xc_sr_set_bit(0, &ctx->x86_hvm.restore.attempted_1g);
>>> +    xc_sr_set_bit(0, &ctx->x86_hvm.restore.attempted_2m);
>> This is false for PVH guests.
> How can I detect a PVH guest?

You (hopefully) can't, and it would be a layering violation if you could.

The exact set of emulation available to/used by a guest is not relevant
to how we move its memory.

If a PVH guest has got MTRRs disabled, then it genuinely can run on an
unshattered 1G superpage at 0.

~Andrew

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