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[62.178.148.172]) by smtp.gmail.com with ESMTPSA id vb9-20020a170907d04900b00a370a76d3a0sm441180ejc.123.2024.02.08.22.40.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Feb 2024 22:40:58 -0800 (PST) From: =?UTF-8?q?Christoph=20M=C3=BCllner?= To: linux-riscv@lists.infradead.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, Jonas Oberhauser , Peter Zijlstra , Palmer Dabbelt , Paul Walmsley , Albert Ou , Andrew Morton , Shuah Khan , Jonathan Corbet , Anup Patel , Philipp Tomsich , Andrew Jones , Guo Ren , Daniel Henrique Barboza , Conor Dooley , =?UTF-8?q?Bj=C3=B6rn=20T=C3=B6pel?= , Alan Stern , Will Deacon , Daniel Lustig , Brendan Sweeney , Andrew Waterman , Brendan Sweeney , Andrea Parri , Hans Boehm Cc: =?UTF-8?q?Christoph=20M=C3=BCllner?= Subject: [RFC PATCH v2 2/6] uapi: prctl: Add new prctl call to set/get the memory consistency model Date: Fri, 9 Feb 2024 07:40:46 +0100 Message-ID: <20240209064050.2746540-3-christoph.muellner@vrull.eu> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240209064050.2746540-1-christoph.muellner@vrull.eu> References: <20240209064050.2746540-1-christoph.muellner@vrull.eu> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable This patch defines a prctl uAPI for switching the active memory consistency model of user-space processes. The implementation follows the way other prctl calls are implemented by disabling them unless arch-specific code provides the relevant macros. Signed-off-by: Christoph M=C3=BCllner --- .../mm/dynamic-memory-consistency-model.rst | 27 +++++++++++++++++++ include/uapi/linux/prctl.h | 3 +++ kernel/sys.c | 12 +++++++++ 3 files changed, 42 insertions(+) diff --git a/Documentation/mm/dynamic-memory-consistency-model.rst b/Docume= ntation/mm/dynamic-memory-consistency-model.rst index 3117c3d82b2b..1fce855a1fad 100644 --- a/Documentation/mm/dynamic-memory-consistency-model.rst +++ b/Documentation/mm/dynamic-memory-consistency-model.rst @@ -47,3 +47,30 @@ at run-time: * Only switching from a weaker to a stronger model is safe. * The stronger memory model affects all threads of a process, when running= in user mode. * Forked processes derive their active memory model from their parents. + +User API via prctl +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D + +Two prctl calls are defined to get/set the active memory consistency model: + +* prctl(PR_GET_MEMORY_CONSISTENCY_MODEL) + + Returns the active memory consistency model for the calling process/th= read. + If the architecture does not support dynamic memory consistency models, + then -1 is returned, and errno is set to EINVAL. + +* prctl(PR_SET_MEMORY_CONSISTENCY_MODEL, unsigned long new_model) + + Switches the memory consistency model for the calling process/thread + to the given model. If the architecture does not support dynamic + memory consistency models, or does not support the provided model, or + does not allow to switch to the proveided model then -1 is returned, + and errno is set to EINVAL. + +Supported memory consistency models +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D + +This section defines the memory consistency models which are supported +by the prctl interface. + + diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h index 370ed14b1ae0..579662731eaa 100644 --- a/include/uapi/linux/prctl.h +++ b/include/uapi/linux/prctl.h @@ -306,4 +306,7 @@ struct prctl_mm_map { # define PR_RISCV_V_VSTATE_CTRL_NEXT_MASK 0xc # define PR_RISCV_V_VSTATE_CTRL_MASK 0x1f =20 +#define PR_SET_MEMORY_CONSISTENCY_MODEL 71 +#define PR_GET_MEMORY_CONSISTENCY_MODEL 72 + #endif /* _LINUX_PRCTL_H */ diff --git a/kernel/sys.c b/kernel/sys.c index e219fcfa112d..a1b92a38f889 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -146,6 +146,12 @@ #ifndef RISCV_V_GET_CONTROL # define RISCV_V_GET_CONTROL() (-EINVAL) #endif +#ifndef SET_MEMORY_CONSISTENCY_MODEL +# define SET_MEMORY_CONSISTENCY_MODEL(a) (-EINVAL) +#endif +#ifndef GET_MEMORY_CONSISTENCY_MODEL +# define GET_MEMORY_CONSISTENCY_MODEL() (-EINVAL) +#endif =20 /* * this is where the system-wide overflow UID and GID are defined, for @@ -2743,6 +2749,12 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, a= rg2, unsigned long, arg3, case PR_RISCV_V_GET_CONTROL: error =3D RISCV_V_GET_CONTROL(); break; + case PR_SET_MEMORY_CONSISTENCY_MODEL: + error =3D SET_MEMORY_CONSISTENCY_MODEL(arg2); + break; + case PR_GET_MEMORY_CONSISTENCY_MODEL: + error =3D GET_MEMORY_CONSISTENCY_MODEL(); + break; default: error =3D -EINVAL; break; --=20 2.43.0