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. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
