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[106.72.41.33]) by smtp.gmail.com with ESMTPSA id m2sm2314432pja.52.2021.07.30.06.52.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 30 Jul 2021 06:52:50 -0700 (PDT) Subject: [PATCH 1/1] riscv: __asm_copy_to-from_user: Improve using word copy if size < 9*SZREG To: Paul Walmsley , Palmer Dabbelt , Guenter Roeck , Geert Uytterhoeven , Qiu Wenbo , Albert Ou , linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org References: <65f08f01-d4ce-75c2-030b-f8759003e061@gmail.com> From: Akira Tsukamoto Message-ID: Date: Fri, 30 Jul 2021 22:52:44 +0900 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.12.0 MIME-Version: 1.0 In-Reply-To: <65f08f01-d4ce-75c2-030b-f8759003e061@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Reduce the number of slow byte_copy when the size is in between 2*SZREG to 9*SZREG by using none unrolled word_copy. Without it any size smaller than 9*SZREG will be using slow byte_copy instead of none unrolled word_copy. Signed-off-by: Akira Tsukamoto --- arch/riscv/lib/uaccess.S | 46 ++++++++++++++++++++++++++++++++++++---- 1 file changed, 42 insertions(+), 4 deletions(-) diff --git a/arch/riscv/lib/uaccess.S b/arch/riscv/lib/uaccess.S index 63bc691cff91..6a80d5517afc 100644 --- a/arch/riscv/lib/uaccess.S +++ b/arch/riscv/lib/uaccess.S @@ -34,8 +34,10 @@ ENTRY(__asm_copy_from_user) /* * Use byte copy only if too small. * SZREG holds 4 for RV32 and 8 for RV64 + * a3 - 2*SZREG is minimum size for word_copy + * 1*SZREG for aligning dst + 1*SZREG for word_copy */ - li a3, 9*SZREG /* size must be larger than size in word_copy */ + li a3, 2*SZREG bltu a2, a3, .Lbyte_copy_tail /* @@ -66,9 +68,40 @@ ENTRY(__asm_copy_from_user) andi a3, a1, SZREG-1 bnez a3, .Lshift_copy +.Lcheck_size_bulk: + /* + * Evaluate the size if possible to use unrolled. + * The word_copy_unlrolled requires larger than 8*SZREG + */ + li a3, 8*SZREG + add a4, a0, a3 + bltu a4, t0, .Lword_copy_unlrolled + .Lword_copy: - /* - * Both src and dst are aligned, unrolled word copy + /* + * Both src and dst are aligned + * None unrolled word copy with every 1*SZREG iteration + * + * a0 - start of aligned dst + * a1 - start of aligned src + * t0 - end of aligned dst + */ + bgeu a0, t0, .Lbyte_copy_tail /* check if end of copy */ + addi t0, t0, -(SZREG) /* not to over run */ +1: + REG_L a5, 0(a1) + addi a1, a1, SZREG + REG_S a5, 0(a0) + addi a0, a0, SZREG + bltu a0, t0, 1b + + addi t0, t0, SZREG /* revert to original value */ + j .Lbyte_copy_tail + +.Lword_copy_unlrolled: + /* + * Both src and dst are aligned + * Unrolled word copy with every 8*SZREG iteration * * a0 - start of aligned dst * a1 - start of aligned src @@ -97,7 +130,12 @@ ENTRY(__asm_copy_from_user) bltu a0, t0, 2b addi t0, t0, 8*SZREG /* revert to original value */ - j .Lbyte_copy_tail + + /* + * Remaining might large enough for word_copy to reduce slow byte + * copy + */ + j .Lcheck_size_bulk .Lshift_copy: -- 2.17.1