From f2d57765b79857264fb0ddc52679d661b60ecc21 Mon Sep 17 00:00:00 2001 From: "Fabio M. De Francesco" Date: Fri, 15 Jul 2022 01:50:30 +0200 Subject: firmware_loader: Replace kmap() with kmap_local_page() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The use of kmap() is being deprecated in favor of kmap_local_page(). Two main problems with kmap(): (1) It comes with an overhead as mapping space is restricted and protected by a global lock for synchronization and (2) kmap() also requires global TLB invalidation when the kmap’s pool wraps and it might block when the mapping space is fully utilized until a slot becomes available. kmap_local_page() is preferred over kmap() and kmap_atomic(). Where it cannot mechanically replace the latters, code refactor should be considered (special care must be taken if kernel virtual addresses are aliases in different contexts). With kmap_local_page() the mappings are per thread, CPU local, can take page faults, and can be called from any context (including interrupts). Call kmap_local_page() in firmware_loader wherever kmap() is currently used. In firmware_rw() use the helpers copy_{from,to}_page() instead of open coding the local mappings + memcpy(). Successfully tested with "firmware" selftests on a QEMU/KVM 32-bits VM with 4GB RAM, booting a kernel with HIGHMEM64GB enabled. Cc: Greg Kroah-Hartman Cc: Luis Chamberlain Suggested-by: Ira Weiny Reviewed-by: Takashi Iwai Signed-off-by: Fabio M. De Francesco Link: https://lore.kernel.org/r/20220714235030.12732-1-fmdefrancesco@gmail.com Signed-off-by: Greg Kroah-Hartman --- drivers/base/firmware_loader/sysfs.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) (limited to 'drivers/base/firmware_loader/sysfs.c') diff --git a/drivers/base/firmware_loader/sysfs.c b/drivers/base/firmware_loader/sysfs.c index 5b0b85b70b6f..77bad32c481a 100644 --- a/drivers/base/firmware_loader/sysfs.c +++ b/drivers/base/firmware_loader/sysfs.c @@ -242,19 +242,17 @@ static void firmware_rw(struct fw_priv *fw_priv, char *buffer, loff_t offset, size_t count, bool read) { while (count) { - void *page_data; int page_nr = offset >> PAGE_SHIFT; int page_ofs = offset & (PAGE_SIZE - 1); int page_cnt = min_t(size_t, PAGE_SIZE - page_ofs, count); - page_data = kmap(fw_priv->pages[page_nr]); - if (read) - memcpy(buffer, page_data + page_ofs, page_cnt); + memcpy_from_page(buffer, fw_priv->pages[page_nr], + page_ofs, page_cnt); else - memcpy(page_data + page_ofs, buffer, page_cnt); + memcpy_to_page(fw_priv->pages[page_nr], page_ofs, + buffer, page_cnt); - kunmap(fw_priv->pages[page_nr]); buffer += page_cnt; offset += page_cnt; count -= page_cnt; -- cgit