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2fb2b7877b
When doing "fast unprotection" of nested TDP page tables, skip emulation
if and only if at least one gfn was unprotected, i.e. continue with
emulation if simply resuming is likely to hit the same fault and risk
putting the vCPU into an infinite loop.
Note, it's entirely possible to get a false negative, e.g. if a different
vCPU faults on the same gfn and unprotects the gfn first, but that's a
relatively rare edge case, and emulating is still functionally ok, i.e.
saving a few cycles by avoiding emulation isn't worth the risk of putting
the vCPU into an infinite loop.
Opportunistically rewrite the relevant comment to document in gory detail
exactly what scenario the "fast unprotect" logic is handling.
Fixes: 147277540b ("kvm: svm: Add support for additional SVM NPF error codes")
Cc: Yuan Yao <yuan.yao@intel.com>
Reviewed-by: Yuan Yao <yuan.yao@intel.com>
Link: https://lore.kernel.org/r/20240831001538.336683-5-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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.