Re: [RFC PATCH] KVM: PPC: BOOK3S: HV: THP support for guest

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 05/06/2014 05:06 PM, Aneesh Kumar K.V wrote:
Alexander Graf <agraf@xxxxxxx> writes:

On 05/06/2014 11:26 AM, Benjamin Herrenschmidt wrote:
On Tue, 2014-05-06 at 11:12 +0200, Alexander Graf wrote:

.....


I updated the commit message as below. Let me know if this is ok.

     KVM: PPC: BOOK3S: HV: THP support for guest

This has nothing to do with THP.

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 advertise MPSS feature to guest only if the host CPU supports the
     same. We use "ibm,segment-page-sizes" device tree node to advertise
     the MPSS support. The penc encoding indicate whether we support
     a specific combination of base page size and actual page size
     in the same segment. It is also the value used in the L|LP encoding
     of HPTE entry.
In-order to support MPSS in guest, KVM need to handle the below details
     * advertise MPSS via ibm,segment-page-sizes
     * Decode the base and actual page size correctly from the HPTE entry
       so that we know what we are dealing with in H_ENTER and and can do

Which code path exactly changes for H_ENTER?

       the appropriate TLB invalidation in H_REMOVE and evictions.

Apart from the grammar (which is pretty broken for the part that is not copied from Paul) and the subject line this sounds quite reasonable.


Alex

--
To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html




[Index of Archives]     [KVM Development]     [KVM ARM]     [KVM ia64]     [Linux Virtualization]     [Linux USB Devel]     [Linux Video]     [Linux Audio Users]     [Linux Kernel]     [Linux SCSI]     [Big List of Linux Books]

  Powered by Linux