Re: [Xen-devel] [PATCHv1] CA-201372: x86: don't flush the whole cache when changing cachability

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 09.03.16 at 19:46, <david.vrabel@xxxxxxxxxx> wrote:
> On 09/03/16 15:23, Jan Beulich wrote:
>> 
>> And there's a second issue here: map_pages_to_xen() updates
>> the idle page tables, only part of which is actually in use on a
>> huge machine in the context of a PV guest, so the above is also
>> risking a #PF on a guest address for the CLFLUSH. Setting the
>> new flag only when the virtual address the mapping of which
>> gets changed is within
>> [DIRECTMAP_VIRT_START, HYPERVISOR_VIRT_END) would
>> seem an acceptable assumption: We know we're never changing
>> the VFN <-> PFN relationship inside the 1:1 mapping.
> 
> Andrew suggested [DIRECTMAP_VIRT_START, DIRECTMAP_VIRT_END) which makes
> more sense to me.

But which is wrong, as it would again cover both the always visible
part and that visible only outside of the context of PV guests.

Jan


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