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There is a need for a do-not-allocate-memory path through the AP bus layer. The pkey layer may be triggered via the in-kernel interface from a protected key crypto algorithm (namely PAES) to convert a secure key into a protected key. This happens in a workqueue context, so sleeping is allowed but memory allocations causing IO operations are not permitted. To accomplish this, an AP message memory pool with pre-allocated space is established. When ap_init_apmsg() with use_mempool set to true is called, instead of kmalloc() the ap message buffer is allocated from the ap_msg_pool. This pool only holds a limited amount of buffers: ap_msg_pool_min_items with the item size AP_DEFAULT_MAX_MSG_SIZE and exactly one of these items (if available) is returned if ap_init_apmsg() with the use_mempool arg set to true is called. When this pool is exhausted and use_mempool is set true, ap_init_apmsg() returns -ENOMEM without any attempt to allocate memory and the caller has to deal with that. Default values for this mempool of ap messages is: * Each buffer is 12KB (that is the default AP bus size and all the urgent messages should fit into this space). * Minimum items held in the pool is 8. This value is adjustable via module parameter ap.msgpool_min_items. The zcrypt layer may use this flag to indicate to the ap bus that the processing path for this message should not allocate memory but should use pre-allocated memory buffer instead. This is to prevent deadlocks with crypto and io for example with encrypted swap volumes. Signed-off-by: Harald Freudenberger <freude@linux.ibm.com> Reviewed-by: Holger Dengler <dengler@linux.ibm.com> Link: https://lore.kernel.org/r/20250424133619.16495-4-freude@linux.ibm.com Signed-off-by: Heiko Carstens <hca@linux.ibm.com> |
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| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .clippy.toml | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.