From ec6347bb43395cb92126788a1a5b25302543f815 Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Mon, 5 Oct 2020 20:40:16 -0700 Subject: x86, powerpc: Rename memcpy_mcsafe() to copy_mc_to_{user, kernel}() In reaction to a proposal to introduce a memcpy_mcsafe_fast() implementation Linus points out that memcpy_mcsafe() is poorly named relative to communicating the scope of the interface. Specifically what addresses are valid to pass as source, destination, and what faults / exceptions are handled. Of particular concern is that even though x86 might be able to handle the semantics of copy_mc_to_user() with its common copy_user_generic() implementation other archs likely need / want an explicit path for this case: On Fri, May 1, 2020 at 11:28 AM Linus Torvalds wrote: > > On Thu, Apr 30, 2020 at 6:21 PM Dan Williams wrote: > > > > However now I see that copy_user_generic() works for the wrong reason. > > It works because the exception on the source address due to poison > > looks no different than a write fault on the user address to the > > caller, it's still just a short copy. So it makes copy_to_user() work > > for the wrong reason relative to the name. > > Right. > > And it won't work that way on other architectures. On x86, we have a > generic function that can take faults on either side, and we use it > for both cases (and for the "in_user" case too), but that's an > artifact of the architecture oddity. > > In fact, it's probably wrong even on x86 - because it can hide bugs - > but writing those things is painful enough that everybody prefers > having just one function. Replace a single top-level memcpy_mcsafe() with either copy_mc_to_user(), or copy_mc_to_kernel(). Introduce an x86 copy_mc_fragile() name as the rename for the low-level x86 implementation formerly named memcpy_mcsafe(). It is used as the slow / careful backend that is supplanted by a fast copy_mc_generic() in a follow-on patch. One side-effect of this reorganization is that separating copy_mc_64.S to its own file means that perf no longer needs to track dependencies for its memcpy_64.S benchmarks. [ bp: Massage a bit. ] Signed-off-by: Dan Williams Signed-off-by: Borislav Petkov Reviewed-by: Tony Luck Acked-by: Michael Ellerman Cc: Link: http://lore.kernel.org/r/CAHk-=wjSqtXAqfUJxFtWNwmguFASTgB0dz1dT3V-78Quiezqbg@mail.gmail.com Link: https://lkml.kernel.org/r/160195561680.2163339.11574962055305783722.stgit@dwillia2-desk3.amr.corp.intel.com --- drivers/md/dm-writecache.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) (limited to 'drivers/md') diff --git a/drivers/md/dm-writecache.c b/drivers/md/dm-writecache.c index 86dbe0c8b45c..9fc18fadacc6 100644 --- a/drivers/md/dm-writecache.c +++ b/drivers/md/dm-writecache.c @@ -49,7 +49,7 @@ do { \ #define pmem_assign(dest, src) ((dest) = (src)) #endif -#if defined(__HAVE_ARCH_MEMCPY_MCSAFE) && defined(DM_WRITECACHE_HAS_PMEM) +#if IS_ENABLED(CONFIG_ARCH_HAS_COPY_MC) && defined(DM_WRITECACHE_HAS_PMEM) #define DM_WRITECACHE_HANDLE_HARDWARE_ERRORS #endif @@ -984,7 +984,8 @@ static void writecache_resume(struct dm_target *ti) } wc->freelist_size = 0; - r = memcpy_mcsafe(&sb_seq_count, &sb(wc)->seq_count, sizeof(uint64_t)); + r = copy_mc_to_kernel(&sb_seq_count, &sb(wc)->seq_count, + sizeof(uint64_t)); if (r) { writecache_error(wc, r, "hardware memory error when reading superblock: %d", r); sb_seq_count = cpu_to_le64(0); @@ -1000,7 +1001,8 @@ static void writecache_resume(struct dm_target *ti) e->seq_count = -1; continue; } - r = memcpy_mcsafe(&wme, memory_entry(wc, e), sizeof(struct wc_memory_entry)); + r = copy_mc_to_kernel(&wme, memory_entry(wc, e), + sizeof(struct wc_memory_entry)); if (r) { writecache_error(wc, r, "hardware memory error when reading metadata entry %lu: %d", (unsigned long)b, r); @@ -1198,7 +1200,7 @@ static void bio_copy_block(struct dm_writecache *wc, struct bio *bio, void *data if (rw == READ) { int r; - r = memcpy_mcsafe(buf, data, size); + r = copy_mc_to_kernel(buf, data, size); flush_dcache_page(bio_page(bio)); if (unlikely(r)) { writecache_error(wc, r, "hardware memory error when reading data: %d", r); @@ -2341,7 +2343,7 @@ invalid_optional: } } - r = memcpy_mcsafe(&s, sb(wc), sizeof(struct wc_memory_superblock)); + r = copy_mc_to_kernel(&s, sb(wc), sizeof(struct wc_memory_superblock)); if (r) { ti->error = "Hardware memory error when reading superblock"; goto bad; @@ -2352,7 +2354,8 @@ invalid_optional: ti->error = "Unable to initialize device"; goto bad; } - r = memcpy_mcsafe(&s, sb(wc), sizeof(struct wc_memory_superblock)); + r = copy_mc_to_kernel(&s, sb(wc), + sizeof(struct wc_memory_superblock)); if (r) { ti->error = "Hardware memory error when reading superblock"; goto bad; -- cgit v1.2.3