From 43c16d51a19b0ba2ed66978d5924d486ec1e42bc Mon Sep 17 00:00:00 2001 From: Andrew Jones Date: Mon, 18 Sep 2023 15:15:21 +0200 Subject: RISC-V: Enable cbo.zero in usermode When Zicboz is present, enable its instruction (cbo.zero) in usermode by setting its respective senvcfg bit. We don't bother trying to set this bit per-task, which would also require an interface for tasks to request enabling and/or disabling. Instead, permanently set the bit for each hart which has the extension when bringing it online. This patch also introduces riscv_cpu_has_extension_[un]likely() functions to check a specific hart's ISA bitmap for extensions. Prior to checking the specific hart's bitmap in these functions we try the bitmap which represents the LCD of extensions, but only when we know it will use its optimized, alternatives path by gating its call on CONFIG_RISCV_ALTERNATIVE. When alternatives are used, the compiler ensures that the invocation of the LCD search becomes a constant true or false. When it's true, even the new functions will completely vanish from their callsites. OTOH, when the LCD check is false, we need to do a search of the hart's ISA bitmap. Had we also checked the LCD bitmap without the use of alternatives, then we would have ended up with two bitmap searches instead of one. Signed-off-by: Andrew Jones Reviewed-by: Conor Dooley Link: https://lore.kernel.org/r/20230918131518.56803-10-ajones@ventanamicro.com Signed-off-by: Palmer Dabbelt --- arch/riscv/kernel/cpufeature.c | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'arch/riscv/kernel/cpufeature.c') diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c index f9ac2717bc7d..8ad6da03ee34 100644 --- a/arch/riscv/kernel/cpufeature.c +++ b/arch/riscv/kernel/cpufeature.c @@ -653,6 +653,12 @@ static int check_unaligned_access_boot_cpu(void) arch_initcall(check_unaligned_access_boot_cpu); +void riscv_user_isa_enable(void) +{ + if (riscv_cpu_has_extension_unlikely(smp_processor_id(), RISCV_ISA_EXT_ZICBOZ)) + csr_set(CSR_SENVCFG, ENVCFG_CBZE); +} + #ifdef CONFIG_RISCV_ALTERNATIVE /* * Alternative patch sites consider 48 bits when determining when to patch -- cgit