TWx Linux Repository
c211c19e80
load_unaligned_zeropad() can lead to unwanted loads across page boundaries. The unwanted loads are typically harmless. But, they might be made to totally unrelated or even unmapped memory. load_unaligned_zeropad() relies on exception fixup (#PF, #GP and now #VE) to recover from these unwanted loads. But, this approach does not work for unaccepted memory. For TDX, a load from unaccepted memory will not lead to a recoverable exception within the guest. The guest will exit to the VMM where the only recourse is to terminate the guest. There are two parts to fix this issue and comprehensively avoid access to unaccepted memory. Together these ensure that an extra "guard" page is accepted in addition to the memory that needs to be used. 1. Implicitly extend the range_contains_unaccepted_memory(start, end) checks up to end+unit_size if 'end' is aligned on a unit_size boundary. 2. Implicitly extend accept_memory(start, end) to end+unit_size if 'end' is aligned on a unit_size boundary. Side note: This leads to something strange. Pages which were accepted at boot, marked by the firmware as accepted and will never _need_ to be accepted might be on unaccepted_pages list This is a cue to ensure that the next page is accepted before 'page' can be used. This is an actual, real-world problem which was discovered during TDX testing. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Ard Biesheuvel <ardb@kernel.org> Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com> Link: https://lore.kernel.org/r/20230606142637.5171-7-kirill.shutemov@linux.intel.com |
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| .clang-format | ||
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| 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.