From aa9695157f65c55e5c85a1c194859d3c03e68018 Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Tue, 13 Dec 2022 17:13:10 +0100 Subject: crypto: scatterwalk - use kmap_local() not kmap_atomic() kmap_atomic() is used to create short-lived mappings of pages that may not be accessible via the kernel direct map. This is only needed on 32-bit architectures that implement CONFIG_HIGHMEM, but it can be used on 64-bit other architectures too, where the returned mapping is simply the kernel direct address of the page. However, kmap_atomic() does not support migration on CONFIG_HIGHMEM configurations, due to the use of per-CPU kmap slots, and so it disables preemption on all architectures, not just the 32-bit ones. This implies that all scatterwalk based crypto routines essentially execute with preemption disabled all the time, which is less than ideal. So let's switch scatterwalk_map/_unmap and the shash/ahash routines to kmap_local() instead, which serves a similar purpose, but without the resulting impact on preemption on architectures that have no need for CONFIG_HIGHMEM. Cc: Eric Biggers Cc: Herbert Xu Cc: "Elliott, Robert (Servers)" Signed-off-by: Ard Biesheuvel Signed-off-by: Herbert Xu --- crypto/ahash.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'crypto/ahash.c') diff --git a/crypto/ahash.c b/crypto/ahash.c index c2ca631a111f..4b089f1b770f 100644 --- a/crypto/ahash.c +++ b/crypto/ahash.c @@ -45,7 +45,7 @@ static int hash_walk_next(struct crypto_hash_walk *walk) unsigned int nbytes = min(walk->entrylen, ((unsigned int)(PAGE_SIZE)) - offset); - walk->data = kmap_atomic(walk->pg); + walk->data = kmap_local_page(walk->pg); walk->data += offset; if (offset & alignmask) { @@ -95,7 +95,7 @@ int crypto_hash_walk_done(struct crypto_hash_walk *walk, int err) } } - kunmap_atomic(walk->data); + kunmap_local(walk->data); crypto_yield(walk->flags); if (err) -- cgit v1.2.3