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AJvYcCX1EvVvL9sUPUvUYW9b0mTyo1p3Ou6GHuNMZScRRrzhK5zPxlaQ9R9SZwwgbaX8yAOlHPWYPV2f9Oiauk5Em/3LocR5kp6IGqXTmmpL X-Gm-Message-State: AOJu0Yy5D+XX0FhcAMS1Xk+dtsHWfaysXICiVdgUJuD8HErXCgDXWH9y O6E4gFy6eZFf6BdOF5WDB7nWCh8k0gy4XaDWVEJOfrzfQ5c9e7TVCRubLXg86wo+UYl+qEiVVX1 H X-Received: by 2002:a05:6870:e2d3:b0:21f:aa70:4c2b with SMTP id w19-20020a056870e2d300b0021faa704c2bmr13648589oad.12.1709103364136; Tue, 27 Feb 2024 22:56:04 -0800 (PST) Received: from sw06.internal.sifive.com ([4.53.31.132]) by smtp.gmail.com with ESMTPSA id e12-20020a62aa0c000000b006e5590729aasm1010112pff.89.2024.02.27.22.56.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 27 Feb 2024 22:56:03 -0800 (PST) From: Samuel Holland To: Palmer Dabbelt Cc: Andrew Jones , linux-kernel@vger.kernel.org, Conor Dooley , Alexandre Ghiti , linux-riscv@lists.infradead.org, Stefan O'Rear , Samuel Holland , stable@vger.kernel.org Subject: [PATCH -fixes v4 2/3] riscv: Add a custom ISA extension for the [ms]envcfg CSR Date: Tue, 27 Feb 2024 22:55:34 -0800 Message-ID: <20240228065559.3434837-3-samuel.holland@sifive.com> X-Mailer: git-send-email 2.43.1 In-Reply-To: <20240228065559.3434837-1-samuel.holland@sifive.com> References: <20240228065559.3434837-1-samuel.holland@sifive.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1792124817131677695 X-GMAIL-MSGID: 1792124817131677695 The [ms]envcfg CSR was added in version 1.12 of the RISC-V privileged ISA (aka S[ms]1p12). However, bits in this CSR are defined by several other extensions which may be implemented separately from any particular version of the privileged ISA (for example, some unrelated errata may prevent an implementation from claiming conformance with Ss1p12). As a result, Linux cannot simply use the privileged ISA version to determine if the CSR is present. It must also check if any of these other extensions are implemented. It also cannot probe the existence of the CSR at runtime, because Linux does not require Sstrict, so (in the absence of additional information) it cannot know if a CSR at that address is [ms]envcfg or part of some non-conforming vendor extension. Since there are several standard extensions that imply the existence of the [ms]envcfg CSR, it becomes unwieldy to check for all of them wherever the CSR is accessed. Instead, define a custom Xlinuxenvcfg ISA extension bit that is implied by the other extensions and denotes that the CSR exists as defined in the privileged ISA, containing at least one of the fields common between menvcfg and senvcfg. This extension does not need to be parsed from the devicetree or ISA string because it can only be implemented as a subset of some other standard extension. Cc: # v6.7+ Signed-off-by: Samuel Holland Reviewed-by: Conor Dooley Reviewed-by: Andrew Jones --- Changes in v4: - New patch for v4 arch/riscv/include/asm/hwcap.h | 2 ++ arch/riscv/kernel/cpufeature.c | 14 ++++++++++++-- 2 files changed, 14 insertions(+), 2 deletions(-) diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h index 5340f818746b..1f2d2599c655 100644 --- a/arch/riscv/include/asm/hwcap.h +++ b/arch/riscv/include/asm/hwcap.h @@ -81,6 +81,8 @@ #define RISCV_ISA_EXT_ZTSO 72 #define RISCV_ISA_EXT_ZACAS 73 +#define RISCV_ISA_EXT_XLINUXENVCFG 127 + #define RISCV_ISA_EXT_MAX 128 #define RISCV_ISA_EXT_INVALID U32_MAX diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c index c5b13f7dd482..dacffef68ce2 100644 --- a/arch/riscv/kernel/cpufeature.c +++ b/arch/riscv/kernel/cpufeature.c @@ -201,6 +201,16 @@ static const unsigned int riscv_zvbb_exts[] = { RISCV_ISA_EXT_ZVKB }; +/* + * While the [ms]envcfg CSRs were not defined until version 1.12 of the RISC-V + * privileged ISA, the existence of the CSRs is implied by any extension which + * specifies [ms]envcfg bit(s). Hence, we define a custom ISA extension for the + * existence of the CSR, and treat it as a subset of those other extensions. + */ +static const unsigned int riscv_xlinuxenvcfg_exts[] = { + RISCV_ISA_EXT_XLINUXENVCFG +}; + /* * The canonical order of ISA extension names in the ISA string is defined in * chapter 27 of the unprivileged specification. @@ -250,8 +260,8 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = { __RISCV_ISA_EXT_DATA(c, RISCV_ISA_EXT_c), __RISCV_ISA_EXT_DATA(v, RISCV_ISA_EXT_v), __RISCV_ISA_EXT_DATA(h, RISCV_ISA_EXT_h), - __RISCV_ISA_EXT_DATA(zicbom, RISCV_ISA_EXT_ZICBOM), - __RISCV_ISA_EXT_DATA(zicboz, RISCV_ISA_EXT_ZICBOZ), + __RISCV_ISA_EXT_SUPERSET(zicbom, RISCV_ISA_EXT_ZICBOM, riscv_xlinuxenvcfg_exts), + __RISCV_ISA_EXT_SUPERSET(zicboz, RISCV_ISA_EXT_ZICBOZ, riscv_xlinuxenvcfg_exts), __RISCV_ISA_EXT_DATA(zicntr, RISCV_ISA_EXT_ZICNTR), __RISCV_ISA_EXT_DATA(zicond, RISCV_ISA_EXT_ZICOND), __RISCV_ISA_EXT_DATA(zicsr, RISCV_ISA_EXT_ZICSR),