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

[David Vrabel <david.vrabel@xxxxxxxxxx>]

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.

David

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