0cb0837f9d
In some configurations of KVM, guests binary patch themselves to avoid/reduce trapping into the hypervisor. For some instructions this requires replacing one instruction with a sequence of instructions. For those cases we need to write the sequence of instructions somewhere and then patch the location of the original instruction to branch to the sequence. That requires that the location of the sequence be within 32MB of the original instruction. The current solution for this is that we create a 1MB array in BSS, write sequences into there, and then free the remainder of the array. This has a few problems: - it confuses kmemleak. - it confuses lockdep. - it requires mapping kvm_tmp executable, which can cause adjacent areas to also be mapped executable if we're using 16M pages for the linear mapping. - the 32MB limit can be exceeded if the kernel is big enough, especially with STRICT_KERNEL_RWX enabled, which then prevents the patching from working at all. We can fix all those problems by making kvm_tmp just a region of regular .text. However currently it's 1MB in size, and we don't want to waste 1MB of text. In practice however I only see ~30KB of kvm_tmp being used even for an allyes_config. So shrink kvm_tmp to 64K, which ought to be enough for everyone, and move it into .text. Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20190911115746.12433-1-mpe@ellerman.id.au |
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| Documentation | ||
| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
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 Restructured Text 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.