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riscv: uaccess: Relax the threshold for fast path

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The bytes copy for unaligned head would cover at most SZREG-1 bytes, so
it's better to set the threshold as >= (SZREG-1 + word_copy stride size)
which equals to 9*SZREG-1.

Signed-off-by: Xiao Wang <xiao.w.wang@intel.com>
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/r/20240313091929.4029960-1-xiao.w.wang@intel.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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Xiao Wang 2024-03-13 17:19:29 +08:00 committed by Palmer Dabbelt
parent f1905946be
commit 9850e73e82
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arch/riscv/lib/uaccess.S
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@ -44,7 +44,7 @@ SYM_FUNC_START(fallback_scalar_usercopy)
* Use byte copy only if too small.
* SZREG holds 4 for RV32 and 8 for RV64
*/
li a3, 9*SZREG /* size must be larger than size in word_copy */
li a3, 9*SZREG-1 /* size must >= (word_copy stride + SZREG-1) */
bltu a2, a3, .Lbyte_copy_tail
/*