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([91.197.138.148]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-442f395166fsm59310785e9.18.2025.05.15.01.23.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 15 May 2025 01:23:50 -0700 (PDT) From: =?UTF-8?q?Cl=C3=A9ment=20L=C3=A9ger?= To: 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 Cc: =?UTF-8?q?Cl=C3=A9ment=20L=C3=A9ger?= , Samuel Holland , Andrew Jones , Deepak Gupta Subject: [PATCH v7 06/14] riscv: misaligned: request misaligned exception from SBI Date: Thu, 15 May 2025 10:22:07 +0200 Message-ID: <20250515082217.433227-7-cleger@rivosinc.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250515082217.433227-1-cleger@rivosinc.com> References: <20250515082217.433227-1-cleger@rivosinc.com> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Now that the kernel can handle misaligned accesses in S-mode, request misaligned access exception delegation from SBI. This uses the FWFT SBI extension defined in SBI version 3.0. Signed-off-by: Clément Léger Reviewed-by: Andrew Jones --- arch/riscv/include/asm/cpufeature.h | 3 +- arch/riscv/kernel/traps_misaligned.c | 71 +++++++++++++++++++++- arch/riscv/kernel/unaligned_access_speed.c | 8 ++- 3 files changed, 77 insertions(+), 5 deletions(-) diff --git a/arch/riscv/include/asm/cpufeature.h b/arch/riscv/include/asm/cpufeature.h index f56b409361fb..dbe5970d4fe6 100644 --- a/arch/riscv/include/asm/cpufeature.h +++ b/arch/riscv/include/asm/cpufeature.h @@ -67,8 +67,9 @@ void __init riscv_user_isa_enable(void); _RISCV_ISA_EXT_DATA(_name, _id, _sub_exts, ARRAY_SIZE(_sub_exts), _validate) bool __init check_unaligned_access_emulated_all_cpus(void); +void unaligned_access_init(void); +int cpu_online_unaligned_access_init(unsigned int cpu); #if defined(CONFIG_RISCV_SCALAR_MISALIGNED) -void check_unaligned_access_emulated(struct work_struct *work __always_unused); void unaligned_emulation_finish(void); bool unaligned_ctl_available(void); DECLARE_PER_CPU(long, misaligned_access_speed); diff --git a/arch/riscv/kernel/traps_misaligned.c b/arch/riscv/kernel/traps_misaligned.c index 77c788660223..592b1a28e897 100644 --- a/arch/riscv/kernel/traps_misaligned.c +++ b/arch/riscv/kernel/traps_misaligned.c @@ -16,6 +16,7 @@ #include #include #include +#include #include #define INSN_MATCH_LB 0x3 @@ -646,7 +647,7 @@ bool __init check_vector_unaligned_access_emulated_all_cpus(void) static bool unaligned_ctl __read_mostly; -void check_unaligned_access_emulated(struct work_struct *work __always_unused) +static void check_unaligned_access_emulated(struct work_struct *work __always_unused) { int cpu = smp_processor_id(); long *mas_ptr = per_cpu_ptr(&misaligned_access_speed, cpu); @@ -657,6 +658,13 @@ void check_unaligned_access_emulated(struct work_struct *work __always_unused) __asm__ __volatile__ ( " "REG_L" %[tmp], 1(%[ptr])\n" : [tmp] "=r" (tmp_val) : [ptr] "r" (&tmp_var) : "memory"); +} + +static int cpu_online_check_unaligned_access_emulated(unsigned int cpu) +{ + long *mas_ptr = per_cpu_ptr(&misaligned_access_speed, cpu); + + check_unaligned_access_emulated(NULL); /* * If unaligned_ctl is already set, this means that we detected that all @@ -665,9 +673,10 @@ void check_unaligned_access_emulated(struct work_struct *work __always_unused) */ if (unlikely(unaligned_ctl && (*mas_ptr != RISCV_HWPROBE_MISALIGNED_SCALAR_EMULATED))) { pr_crit("CPU misaligned accesses non homogeneous (expected all emulated)\n"); - while (true) - cpu_relax(); + return -EINVAL; } + + return 0; } bool __init check_unaligned_access_emulated_all_cpus(void) @@ -699,4 +708,60 @@ bool __init check_unaligned_access_emulated_all_cpus(void) { return false; } +static int cpu_online_check_unaligned_access_emulated(unsigned int cpu) +{ + return 0; +} +#endif + +#ifdef CONFIG_RISCV_SBI + +static bool misaligned_traps_delegated; + +static int cpu_online_sbi_unaligned_setup(unsigned int cpu) +{ + if (sbi_fwft_set(SBI_FWFT_MISALIGNED_EXC_DELEG, 1, 0) && + misaligned_traps_delegated) { + pr_crit("Misaligned trap delegation non homogeneous (expected delegated)"); + return -EINVAL; + } + + return 0; +} + +void __init unaligned_access_init(void) +{ + int ret; + + ret = sbi_fwft_set_online_cpus(SBI_FWFT_MISALIGNED_EXC_DELEG, 1, 0); + if (ret) + return; + + misaligned_traps_delegated = true; + pr_info("SBI misaligned access exception delegation ok\n"); + /* + * Note that we don't have to take any specific action here, if + * the delegation is successful, then + * check_unaligned_access_emulated() will verify that indeed the + * platform traps on misaligned accesses. + */ +} +#else +void __init unaligned_access_init(void) {} + +static int cpu_online_sbi_unaligned_setup(unsigned int cpu __always_unused) +{ + return 0; +} #endif + +int cpu_online_unaligned_access_init(unsigned int cpu) +{ + int ret; + + ret = cpu_online_sbi_unaligned_setup(cpu); + if (ret) + return ret; + + return cpu_online_check_unaligned_access_emulated(cpu); +} diff --git a/arch/riscv/kernel/unaligned_access_speed.c b/arch/riscv/kernel/unaligned_access_speed.c index b8ba13819d05..ae2068425fbc 100644 --- a/arch/riscv/kernel/unaligned_access_speed.c +++ b/arch/riscv/kernel/unaligned_access_speed.c @@ -236,6 +236,11 @@ arch_initcall_sync(lock_and_set_unaligned_access_static_branch); static int riscv_online_cpu(unsigned int cpu) { + int ret = cpu_online_unaligned_access_init(cpu); + + if (ret) + return ret; + /* We are already set since the last check */ if (per_cpu(misaligned_access_speed, cpu) != RISCV_HWPROBE_MISALIGNED_SCALAR_UNKNOWN) { goto exit; @@ -248,7 +253,6 @@ static int riscv_online_cpu(unsigned int cpu) { static struct page *buf; - check_unaligned_access_emulated(NULL); buf = alloc_pages(GFP_KERNEL, MISALIGNED_BUFFER_ORDER); if (!buf) { pr_warn("Allocation failure, not measuring misaligned performance\n"); @@ -439,6 +443,8 @@ static int __init check_unaligned_access_all_cpus(void) { int cpu; + unaligned_access_init(); + if (unaligned_scalar_speed_param != RISCV_HWPROBE_MISALIGNED_SCALAR_UNKNOWN) { pr_info("scalar unaligned access speed set to '%s' (%lu) by command line\n", speed_str[unaligned_scalar_speed_param], unaligned_scalar_speed_param); -- 2.49.0