Re: [PATCH V2] KVM: PPC: BOOK3S: HV: Add mixed page-size support for guest

[Alexander Graf <agraf@suse.de>]

On 05/06/2014 08:01 PM, Aneesh Kumar K.V wrote:
> On recent IBM Power CPUs, while the hashed page table is looked up using
> the page size from the segmentation hardware (i.e. the SLB), it is
> possible to have the HPT entry indicate a larger page size.  Thus for
> example it is possible to put a 16MB page in a 64kB segment, but since
> the hash lookup is done using a 64kB page size, it may be necessary to
> put multiple entries in the HPT for a single 16MB page.  This
> capability is called mixed page-size segment (MPSS).  With MPSS,
> there are two relevant page sizes: the base page size, which is the
> size used in searching the HPT, and the actual page size, which is the
> size indicated in the HPT entry. [ Note that the actual page size is
> always >= base page size ].
>
> We use "ibm,segment-page-sizes" device tree node to advertise
> the MPSS support to PAPR guest. The penc encoding indicates whether
> we support a specific combination of base page size and actual
> page size in the same segment. We also use the penc value in the
> LP encoding of HPTE entry.
>
> This patch exposes MPSS support to KVM guest by advertising the
> feature via "ibm,segment-page-sizes". It also adds the necessary changes
> to decode the base page size and the actual page size correctly from the
> HPTE entry.
>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

Thanks, applied to kvm-ppc-queue.


Alex