This series tries to optimize riscv uaccess by allowing the use ofFollowing up on Ben's comment here https://lore.kernel.org/linux-riscv/b45aab1e-6d37-4027-9a15-4fa917d806b9@xxxxxxxxxxxxxxx/
user_access_begin() and user_access_end() which permits grouping user accesses
and avoiding the CSR write penalty for each access.
The error path can also be optimised using asm goto which patches 3 and 4
achieve. This will speed up jumping to labels by avoiding the need of an
intermediary error type variable within the uaccess macros
I did read the discussion this series generated. It isn't clear to me
which direction to take the patches, if any.
V2:
I've taken on this series as there isn't any response from Jisheng. No
significant changes other than build fixes.
- Fixes build breakage in patch 3 to do with not having used 'goto' keyword.
- Fixes build breakage in patch 4 on 32bit not having delcared __ptr in the
macro.
V3:
Significant commit message rewrites.
- Corrected the justification for patch 2
- Better explained/justified patches 3 and 4
Minor code changes for legibility and more comments.
Jisheng Zhang (4):
riscv: implement user_access_begin() and families
riscv: uaccess: use input constraints for ptr of __put_user()
riscv: uaccess: use 'asm goto' for put_user()
riscv: uaccess: use 'asm_goto_output' for get_user()
arch/riscv/include/asm/uaccess.h | 205 +++++++++++++++++++++++--------
1 file changed, 152 insertions(+), 53 deletions(-)