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Thu, 26 Oct 2023 03:24:42 +0000 (UTC) From: Nathan Lynch via B4 Relay Subject: [PATCH v3 00/10] powerpc/pseries: New character devices for system parameters and VPD Date: Wed, 25 Oct 2023 22:24:14 -0500 Message-Id: <20231025-papr-sys_rtas-vs-lockdown-v3-0-5eb04559e7d8@linux.ibm.com> MIME-Version: 1.0 X-B4-Tracking: v=1; b=H4sIAN7bOWUC/4XOQQ7CIBAF0KsY1mKGwVJ15T2MMUCnSrSlAUWbp neXGuPChS7/JPP+H1ik4CiyzWxggZKLzrc5yPmM2ZNuj8RdlTNDQAkrUfJOd4HHPh7CVUeeIr9 4e678veWFLZYFFJUp18jyfxeodo+XvdvnfHLx6kP/qkpiur5VxB9qEhz4WqJCaWtpS7O9uPb2W DjTLKxvpqJJEQDqnyK1VKY2ShHSlzLtS/jZJEDIXxpmjXQFwhKIEvFbG8fxCcUOR75aAQAA To: Michael Ellerman , Nicholas Piggin X-Mailer: b4 0.12.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1698290680; l=4920; i=nathanl@linux.ibm.com; s=20230817; h=from:subject:message-id; bh=NFrzlpbJn6Fc8OWDOeBcsMej+VBXx++9QWjmXSI+Jys=; b=nEthyzViGh9xUiIfOF9rSAOWO6nSP4erLXnMlxxQtn9o08OLVrMRYXrKv2Fey30zfvP1n1er/ emPtSslOq59Dq7Um4CAOfmWy1IvNWKwoKlbcm5kKdaAuucLdbIcUIS9 X-Developer-Key: i=nathanl@linux.ibm.com; a=ed25519; pk=jPDF44RvT+9DGFOH3NGoIu1xN9dF+82pjdpnKjXfoJ0= X-Endpoint-Received: by B4 Relay for nathanl@linux.ibm.com/20230817 with auth_id=78 X-Original-From: Nathan Lynch X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: nathanl@linux.ibm.com Cc: Nathan Lynch , tyreld@linux.ibm.com, =?utf-8?q?Mi?= =?utf-8?q?chal_Such=C3=A1nek?= , linuxppc-dev@lists.ozlabs.org, gcwilson@linux.ibm.com Errors-To: linuxppc-dev-bounces+incoming=patchwork.ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" Add character devices that expose PAPR-specific system parameters and VPD to user space. The problem: important platform features are enabled on Linux VMs through the powerpc-specific rtas() syscall in combination with writeable mappings of /dev/mem. In typical usage, this is encapsulated behind APIs provided by the librtas library. This paradigm is incompatible with lockdown, which prohibits /dev/mem access. It also is too low-level in many cases: a single logical operation may require multiple sys_rtas() calls in succession to complete. This carries the risk that a process may exit while leaving an operation unfinished. It also means that callers must coordinate their use of the syscall for functions that cannot tolerate multiple concurrent clients, such as ibm,get-vpd. The solution presented here is to add a pair of small pseries-specific "drivers," one for VPD and one for system parameters. The new drivers expose these facilities to user space in ways that are compatible with lockdown and require no coordination between their clients. Since the ibm,get-vpd call sequence performed by the papr-vpd driver must be serialized against all other uses of the function, the series begins by adding some new APIs to the core RTAS support code for this purpose. Both drivers could potentially support poll() methods to notify clients of changes to parameters or VPD that happen due to partition migration and other events. But that should be safe to leave for later, assuming there's any interest. I have made changes to librtas to prefer the new interfaces and verified that existing clients work correctly with the new code. A draft PR for that work is here: https://github.com/ibm-power-utilities/librtas/pull/36 The user-space ABI has not changed since v1 of this series. I expect to propose at least one more small driver in this style for platform dump retrieval in a separate submission in the future. --- Changes in v3: - Add new rtas_function_lock()/unlock() APIs and convert existing code to use them. - Convert papr-vpd to use rtas_function_lock()/unlock() instead of having sys_rtas() obtain a driver-private mutex. - Rebase on current powerpc/next. - Link to v2: https://lore.kernel.org/r/20231013-papr-sys_rtas-vs-lockdown-v2-0-ead01ce01722@linux.ibm.com Changes in v2: - Fix unused-but-set variable warning in papr-sysparm code. - Rebase on powerpc/next branch. - Link to v1: https://lore.kernel.org/r/20231006-papr-sys_rtas-vs-lockdown-v1-0-3a36bfb66e2e@linux.ibm.com Changes in v1 vs initial RFC: - Add papr-sysparm driver and tests. - Add a papr-miscdev.h uapi header. - Prevent sys_rtas() from interfering with papr-vpd call sequences. - Handle -4 ("VPD changed") status in papr-vpd. - Include string_helpers.h in papr-vpd.c, per Michal Suchánek - Link to RFC: https://lore.kernel.org/r/20230822-papr-sys_rtas-vs-lockdown-v1-0-932623cf3c7b@linux.ibm.com --- Nathan Lynch (10): powerpc/rtas: Factor out function descriptor lookup powerpc/rtas: Facilitate high-level call sequences powerpc/rtas: Serialize firmware activation sequences powerpc/rtas: Warn if per-function lock isn't held powerpc/uapi: Export papr-miscdev.h header powerpc/pseries: Add papr-vpd character driver for VPD retrieval powerpc/pseries/papr-sysparm: Validate buffer object lengths powerpc/pseries/papr-sysparm: Expose character device to user space powerpc/selftests: Add test for papr-vpd powerpc/selftests: Add test for papr-sysparm Documentation/userspace-api/ioctl/ioctl-number.rst | 4 + arch/powerpc/include/asm/papr-sysparm.h | 17 +- arch/powerpc/include/asm/rtas.h | 2 + arch/powerpc/include/uapi/asm/papr-miscdev.h | 9 + arch/powerpc/include/uapi/asm/papr-sysparm.h | 58 +++ arch/powerpc/include/uapi/asm/papr-vpd.h | 22 + arch/powerpc/kernel/rtas.c | 157 ++++++- arch/powerpc/platforms/pseries/Makefile | 1 + arch/powerpc/platforms/pseries/papr-sysparm.c | 201 +++++++- arch/powerpc/platforms/pseries/papr-vpd.c | 522 +++++++++++++++++++++ tools/testing/selftests/powerpc/Makefile | 2 + .../selftests/powerpc/papr_sysparm/.gitignore | 1 + .../selftests/powerpc/papr_sysparm/Makefile | 12 + .../selftests/powerpc/papr_sysparm/papr_sysparm.c | 164 +++++++ .../testing/selftests/powerpc/papr_vpd/.gitignore | 1 + tools/testing/selftests/powerpc/papr_vpd/Makefile | 12 + .../testing/selftests/powerpc/papr_vpd/papr_vpd.c | 352 ++++++++++++++ 17 files changed, 1503 insertions(+), 34 deletions(-) --- base-commit: 36e826b568e412f61d68fedc02a67b4d8b7583cc change-id: 20230817-papr-sys_rtas-vs-lockdown-5c54505db792 Best regards,