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Currently memremap(MEMREMAP_WB) can produce decrypted/shared mapping:
memremap(MEMREMAP_WB)
arch_memremap_wb()
ioremap_cache()
__ioremap_caller(.encrytped = false)
In such cases, the IORES_MAP_ENCRYPTED flag on the memory will determine
if the resulting mapping is encrypted or decrypted.
Creating a decrypted mapping without explicit request from the caller is
risky:
- It can inadvertently expose the guest's data and compromise the
guest.
- Accessing private memory via shared/decrypted mapping on TDX will
either trigger implicit conversion to shared or #VE (depending on
VMM implementation).
Implicit conversion is destructive: subsequent access to the same
memory via private mapping will trigger a hard-to-debug #VE crash.
The kernel already provides a way to request decrypted mapping
explicitly via the MEMREMAP_DEC flag.
Modify memremap(MEMREMAP_WB) to produce encrypted/private mapping by
default unless MEMREMAP_DEC is specified or if the kernel runs on
a machine with SME enabled.
It fixes the crash due to #VE on kexec in TDX guests if CONFIG_EISA is
enabled.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linux-mm@kvack.org
Link: https://lore.kernel.org/r/20250217163822.343400-3-kirill.shutemov@linux.intel.com
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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.