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Until now the papr_sysparm APIs have been kernel-internal. But user space needs access to PAPR system parameters too. The only method available to user space today to get or set system parameters is using sys_rtas() and /dev/mem to pass RTAS-addressable buffers between user space and firmware. This is incompatible with lockdown and should be deprecated. So provide an alternative ABI to user space in the form of a /dev/papr-sysparm character device with just two ioctl commands (get and set). The data payloads involved are small enough to fit in the ioctl argument buffer, making the code relatively simple. Exposing the system parameters through sysfs has been considered but it would be too awkward: * The kernel currently does not have to contain an exhaustive list of defined system parameters. This is a convenient property to maintain because we don't have to update the kernel whenever a new parameter is added to PAPR. Exporting a named attribute in sysfs for each parameter would negate this. * Some system parameters are text-based and some are not. * Retrieval of at least one system parameter requires input data, which a simple read-oriented interface can't support. Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://msgid.link/20231212-papr-sys_rtas-vs-lockdown-v6-11-e9eafd0c8c6c@linux.ibm.com |
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| accelerators | ||
| ebpf | ||
| ioctl | ||
| media | ||
| netlink | ||
| dma-buf-alloc-exchange.rst | ||
| ELF.rst | ||
| futex2.rst | ||
| index.rst | ||
| iommu.rst | ||
| iommufd.rst | ||
| landlock.rst | ||
| no_new_privs.rst | ||
| seccomp_filter.rst | ||
| spec_ctrl.rst | ||
| sysfs-platform_profile.rst | ||
| unshare.rst | ||
| vduse.rst | ||