Re: [Xen-devel] [PATCH 11/12] xen/gntdev: mark userspace PTEs as special on x86 PV guests

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2015-01-06 at 18:57 +0000, David Vrabel wrote:
> In an x86 PV guest, get_user_pages_fast() on a userspace address range
> containing foreign mappings does not work correctly because the M2P
> lookup of the MFN from a userspace PTE may return the wrong page.
> 
> Force get_user_pages_fast() to fail on such addresses by marking the PTEs
> as special.
> 
> If Xen has XENFEAT_gnttab_map_avail_bits (available since at least
> 4.0),

http://wiki.xenproject.org/wiki/Xen_Kernel_Feature_Matrix says the dom0
pvpops already requires >= 4.0 too, which matches my recollection
(something to do with a new APIC interface which upstream insisted on
during upstreaming, IIRC), but both could be out of date...

Ian.


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