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[ Upstream commited290e1c20] Though gcc conveniently compiles a simple memset to "rep stos," clang prefers to call the libc version of memset. If a test is dynamically linked, the libc memset isn't available in L1 (nor is the PLT or the GOT, for that matter). Even if the test is statically linked, the libc memset may choose to use some CPU features, like AVX, which may not be enabled in L1. Note that __builtin_memset doesn't solve the problem, because (a) the compiler is free to call memset anyway, and (b) __builtin_memset may also choose to use features like AVX, which may not be available in L1. To avoid a myriad of problems, use an explicit "rep stos" to clear the VMCB in generic_svm_setup(), which is called both from L0 and L1. Reported-by: Ricardo Koller <ricarkol@google.com> Signed-off-by: Jim Mattson <jmattson@google.com> Fixes:20ba262f86("selftests: KVM: AMD Nested test infrastructure") Message-Id: <20210930003649.4026553-1-jmattson@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
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.