linux

iv/linux

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Fabio M. De Francesco f2d57765b7 firmware_loader: Replace kmap() with kmap_local_page()

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 <gregkh@linuxfoundation.org>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Suggested-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Link: https://lore.kernel.org/r/20220714235030.12732-1-fmdefrancesco@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2022-07-28 16:32:56 +02:00

builtin

kbuild: do not quote string values in include/config/auto.conf

2022-01-08 18:03:57 +09:00

fallback_platform.c

firmware: Store opt_flags in fw_priv

2020-10-05 13:37:04 +02:00

fallback_table.c

firmware_loader: move firmware sysctl to its own files

2022-01-22 08:33:35 +02:00

fallback.c

firmware_loader: Split sysfs support from fallback