Paul Mackerras <paulus@xxxxxxxxx> writes: > On Mon, May 05, 2014 at 08:17:00PM +0530, Aneesh Kumar K.V wrote: >> Alexander Graf <agraf@xxxxxxx> writes: >> >> > On 05/04/2014 07:30 PM, Aneesh Kumar K.V wrote: >> >> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx> >> > >> > No patch description, no proper explanations anywhere why you're doing >> > what. All of that in a pretty sensitive piece of code. There's no way >> > this patch can go upstream in its current form. >> > >> >> Sorry about being vague. Will add a better commit message. The goal is >> to export MPSS support to guest if the host support the same. MPSS >> support is exported via penc encoding in "ibm,segment-page-sizes". The >> actual format can be found at htab_dt_scan_page_sizes. When the guest >> memory is backed by hugetlbfs we expose the penc encoding the host >> support to guest via kvmppc_add_seg_page_size. > > In a case like this it's good to assume the reader doesn't know very > much about Power CPUs, and probably isn't familiar with acronyms such > as MPSS. The patch needs an introductory paragraph explaining that 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. I will update the commit message with the above details -aneesh -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
