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Message-Id: <20250318061514.1223111-1-cyrilbur@tenstorrent.com>
Date: Tue, 18 Mar 2025 06:15:09 +0000
From: Cyril Bur <cyrilbur@...storrent.com>
To: palmer@...belt.com,
aou@...s.berkeley.edu,
paul.walmsley@...ive.com,
charlie@...osinc.com,
jrtc27@...c27.com,
ben.dooks@...ethink.co.uk,
alex@...ti.fr
Cc: linux-riscv@...ts.infradead.org,
linux-kernel@...r.kernel.org,
jszhang@...nel.org
Subject: [PATCH v4 0/5] riscv: uaccess: optimizations
This series tries to optimize riscv uaccess by allowing the use of
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
V4:
Fixed checkpatch errors
Added a unsafe_copy_from_user()
Added patch from Ben Dooks to save SR_SUM bit on switch
Ben Dooks (1):
riscv: save the SR_SUM status over switches
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/processor.h | 1 +
arch/riscv/include/asm/uaccess.h | 218 ++++++++++++++++++++++-------
arch/riscv/kernel/asm-offsets.c | 5 +
arch/riscv/kernel/entry.S | 8 ++
4 files changed, 179 insertions(+), 53 deletions(-)
--
2.34.1
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