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[174.21.81.121]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-20bef7fbca9sm12537755ad.238.2024.10.03.13.13.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 03 Oct 2024 13:13:56 -0700 (PDT) Message-ID: <163e6cfc-755e-487d-8653-a5524876e171@linaro.org> Date: Thu, 3 Oct 2024 13:13:55 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] target/riscv/csr.c: Fix an access to VXSAT To: Evgenii Prokopiev , alistair23@gmail.com Cc: alistair.francis@wdc.com, bmeng.cn@gmail.com, dbarboza@ventanamicro.com, liwei1518@gmail.com, palmer@dabbelt.com, qemu-devel@nongnu.org, qemu-riscv@nongnu.org, zhiwei_liu@linux.alibaba.com References: <20241002084436.89347-1-evgenii.prokopiev@syntacore.com> Content-Language: en-US From: Richard Henderson In-Reply-To: <20241002084436.89347-1-evgenii.prokopiev@syntacore.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2607:f8b0:4864:20::632; envelope-from=richard.henderson@linaro.org; helo=mail-pl1-x632.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 10/2/24 01:44, Evgenii Prokopiev wrote: > The register VXSAT should be RW only to the first bit. > The remaining bits should be 0. > > The RISC-V Instruction Set Manual Volume I: Unprivileged Architecture > > The vxsat CSR has a single read-write least-significant bit (vxsat[0]) > that indicates if a fixed-point instruction has had to saturate an output > value to fit into a destination format. Bits vxsat[XLEN-1:1] > should be written as zeros. > > Signed-off-by: Evgenii Prokopiev > Reviewed-by: Daniel Henrique Barboza > Reviewed-by: Alistair Francis > --- > Changes since v2: > - Added reviewed-by tag > target/riscv/csr.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) New versions should not be replies to previous versions. No need to re-spin *only* to collect tags; tools can do that. > > diff --git a/target/riscv/csr.c b/target/riscv/csr.c > index bd080f92b5..69c41212e9 100644 > --- a/target/riscv/csr.c > +++ b/target/riscv/csr.c > @@ -717,7 +717,7 @@ static RISCVException write_vxrm(CPURISCVState *env, int csrno, > static RISCVException read_vxsat(CPURISCVState *env, int csrno, > target_ulong *val) > { > - *val = env->vxsat; > + *val = env->vxsat & BIT(0); > return RISCV_EXCP_NONE; > } Nit: no need to mask on read... > > @@ -727,7 +727,7 @@ static RISCVException write_vxsat(CPURISCVState *env, int csrno, > #if !defined(CONFIG_USER_ONLY) > env->mstatus |= MSTATUS_VS; > #endif > - env->vxsat = val; > + env->vxsat = val & BIT(0); > return RISCV_EXCP_NONE; > } ... because you know the value is already correct from the write. r~