Messages in this thread | | | Subject | Re: [PATCH v3 3/3] mm/hmm/test: add self tests for HMM | From | Ralph Campbell <> | Date | Thu, 31 Oct 2019 10:28:12 -0700 |
| |
On 10/31/19 5:42 AM, Jason Gunthorpe wrote: > On Wed, Oct 30, 2019 at 05:14:30PM -0700, Ralph Campbell wrote: > >>> Well, that is good, is it also under drivers/char? It kind feels like >>> it should not be there... >> >> I think most of the test modules live in lib/ but I wasn't sure that >> was the right place for the HMM test driver. >> If you think that is better, I can easily move it. > > It would be good to get the various test people involved in this, I > really don't know.
OK.
>>>>> It seems especially over-complicated to use a full page table layout >>>>> for this, wouldn't something simple like an xarray be good enough for >>>>> test purposes? >>>> >>>> Possibly. A page table is really just a lookup table from virtual address >>>> to pfn/page. Part of the rationale was to mimic what a real device >>>> might do. >>> >>> Well, but the details of the page table layout don't see really >>> important to this testing, IMHO. >> >> One problem with XArray is that on 32-bit machines the value would >> need to be u64 to hold a pfn which won't fit in a ULONG_MAX. >> I guess we could make the driver 64-bit only. > > Why would a 32 bit machine need a 64 bit pfn? > > Jason >
On x86, Physical Address Extension (PAE) uses a 64 bit PTE. See arch/x86/include/asm/pgtable_32_types.h which includes arch/x86/include/asm/pgtable-3level_types.h.
| |