* Dan Williams <[email protected]> wrote: > The pmem driver has a need to transfer data with a persistent memory > destination and be able to rely on the fact that the destination writes > are not cached. It is sufficient for the writes to be flushed to a > cpu-store-buffer (non-temporal / "movnt" in x86 terms), as we expect > userspace to call fsync() to ensure data-writes have reached a > power-fail-safe zone in the platform. The fsync() triggers a REQ_FUA or > REQ_FLUSH to the pmem driver which will turn around and fence previous > writes with an "sfence". > > Implement a __copy_from_user_inatomic_wt, memcpy_page_wt, and memcpy_wt, > that guarantee that the destination buffer is not dirty in the cpu cache > on completion. The new copy_from_iter_wt and sub-routines will be used > to replace the "pmem api" (include/linux/pmem.h + > arch/x86/include/asm/pmem.h). The availability of copy_from_iter_wt() > and memcpy_wt() are gated by the CONFIG_ARCH_HAS_UACCESS_WT config > symbol, and fallback to copy_from_iter_nocache() and plain memcpy() > otherwise. > > This is meant to satisfy the concern from Linus that if a driver wants > to do something beyond the normal nocache semantics it should be > something private to that driver [1], and Al's concern that anything > uaccess related belongs with the rest of the uaccess code [2]. > > [1]: https://lists.01.org/pipermail/linux-nvdimm/2017-January/008364.html > [2]: https://lists.01.org/pipermail/linux-nvdimm/2017-April/009942.html > > Cc: <[email protected]> > Cc: Jan Kara <[email protected]> > Cc: Jeff Moyer <[email protected]> > Cc: Ingo Molnar <[email protected]> > Cc: Christoph Hellwig <[email protected]> > Cc: "H. Peter Anvin" <[email protected]> > Cc: Al Viro <[email protected]> > Cc: Thomas Gleixner <[email protected]> > Cc: Matthew Wilcox <[email protected]> > Cc: Ross Zwisler <[email protected]> > Signed-off-by: Dan Williams <[email protected]> > --- > Changes since the initial RFC: > * s/writethru/wt/ since we already have ioremap_wt(), set_memory_wt(), > etc. (Ingo)
Looks good to me. I suspect you'd like to carry this in the nvdimm tree? Acked-by: Ingo Molnar <[email protected]> Thanks, Ingo
