On Thu, 9 Nov 2017, Dan Williams wrote: > On Thu, Nov 9, 2017 at 8:40 AM, Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote: > > > > > > On Wed, 8 Nov 2017, Dan Williams wrote: > > > >> On Wed, Nov 8, 2017 at 12:15 PM, Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote: > >> > > >> > > >> > On Wed, 8 Nov 2017, Dan Williams wrote: > >> > > >> >> On Wed, Nov 8, 2017 at 7:35 AM, Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote: > >> >> > On Wed, Nov 08, 2017 at 10:21:38AM -0500, Mikulas Patocka wrote: > >> >> >> > And what do you do for an architecture with virtuall indexed caches? > >> >> >> > >> >> >> Persistent memory is not supported on such architectures - it is only > >> >> >> supported on x86-64 and arm64. > >> >> > > >> >> > For now. But once support is added your driver will just corrupt data > >> >> > unless you have the right API in place. > >> >> > >> >> I'm also in the process of ripping out page-less dax support. With > >> >> pages we can potentially leverage the VIVT-cache support in some > >> >> architectures, likely with more supporting infrastructure for > >> >> dax_flush(). > >> > > >> > Should I remove all the code for page-less persistent memory from my > >> > driver? > >> > > >> > >> Yes, that would be my recommendation. You can see that filesystem-dax > >> is on its way to dropping page-less support in this series: > >> > >> https://lists.01.org/pipermail/linux-nvdimm/2017-October/013125.html > > > > Why do you indend to drop dax for ramdisk? It's perfect for testing. > > > > On x86, persistent memory can be tested with the memmap kernel parameters, > > but on other architectures, ramdisk is the only option for tests. > > > > Because it's not "perfect for testing", it does not support the > get_user_pages() model that we need to safely handle DAX dma. ARM64 > and PowerPC PMEM support is in the works, so I expect the architecture > support landscape for major architectures to improve such that the > pmem driver can always be used for DAX testing. Yes - but if I want to test the persistent memory driver on big-endian machine, I could use an old Sparc or PA-RISC machine with ramdisk. New PowerPC machines may support native persistent memory, but they are extremely expensive. Mikulas -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
