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([2a01:e0a:e17:9700:16d2:7456:6634:9626]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-742a98770cdsm13178352b3a.151.2025.05.23.12.21.54 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 23 May 2025 12:22:02 -0700 (PDT) Message-ID: Date: Fri, 23 May 2025 21:21:51 +0200 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v8 09/14] riscv: misaligned: move emulated access uniformity check in a function To: Charlie Jenkins Cc: Paul Walmsley , Palmer Dabbelt , Anup Patel , Atish Patra , Shuah Khan , Jonathan Corbet , linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, kvm@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-kselftest@vger.kernel.org, Samuel Holland , Andrew Jones , Deepak Gupta References: <20250523101932.1594077-1-cleger@rivosinc.com> <20250523101932.1594077-10-cleger@rivosinc.com> Content-Language: en-US From: =?UTF-8?B?Q2zDqW1lbnQgTMOpZ2Vy?= In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 23/05/2025 20:30, Charlie Jenkins wrote: > On Fri, May 23, 2025 at 12:19:26PM +0200, Clément Léger wrote: >> Split the code that check for the uniformity of misaligned accesses >> performance on all cpus from check_unaligned_access_emulated_all_cpus() >> to its own function which will be used for delegation check. No >> functional changes intended. >> >> Signed-off-by: Clément Léger >> Reviewed-by: Andrew Jones >> --- >> arch/riscv/kernel/traps_misaligned.c | 20 ++++++++++++++------ >> 1 file changed, 14 insertions(+), 6 deletions(-) >> >> diff --git a/arch/riscv/kernel/traps_misaligned.c b/arch/riscv/kernel/traps_misaligned.c >> index f1b2af515592..7ecaa8103fe7 100644 >> --- a/arch/riscv/kernel/traps_misaligned.c >> +++ b/arch/riscv/kernel/traps_misaligned.c >> @@ -645,6 +645,18 @@ bool __init check_vector_unaligned_access_emulated_all_cpus(void) >> } >> #endif >> >> +static bool all_cpus_unaligned_scalar_access_emulated(void) >> +{ >> + int cpu; >> + >> + for_each_online_cpu(cpu) >> + if (per_cpu(misaligned_access_speed, cpu) != >> + RISCV_HWPROBE_MISALIGNED_SCALAR_EMULATED) >> + return false; >> + >> + return true; >> +} > > This ends up wasting time when !CONFIG_RISCV_SCALAR_MISALIGNED since it > will always return false in that case. Maybe there is a way to simplify > the ifdefs and still have performant code, but I don't think this is a > big enough problem to prevent this patch from merging. Yeah I though of that as well but the amount of call to this function is probably well below 10 times so I guess it does not really matters in that case to justify yet another ifdef ? > > Reviewed-by: Charlie Jenkins > Tested-by: Charlie Jenkins Thanks, Clément > >> + >> #ifdef CONFIG_RISCV_SCALAR_MISALIGNED >> >> static bool unaligned_ctl __read_mostly; >> @@ -683,8 +695,6 @@ static int cpu_online_check_unaligned_access_emulated(unsigned int cpu) >> >> bool __init check_unaligned_access_emulated_all_cpus(void) >> { >> - int cpu; >> - >> /* >> * We can only support PR_UNALIGN controls if all CPUs have misaligned >> * accesses emulated since tasks requesting such control can run on any >> @@ -692,10 +702,8 @@ bool __init check_unaligned_access_emulated_all_cpus(void) >> */ >> on_each_cpu(check_unaligned_access_emulated, NULL, 1); >> >> - for_each_online_cpu(cpu) >> - if (per_cpu(misaligned_access_speed, cpu) >> - != RISCV_HWPROBE_MISALIGNED_SCALAR_EMULATED) >> - return false; >> + if (!all_cpus_unaligned_scalar_access_emulated()) >> + return false; >> >> unaligned_ctl = true; >> return true; >> -- >> 2.49.0 >>