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commit0e0ab73c9aupstream. ...except RSP, which is restored by hardware as part of VM-Exit. Paolo theorized that restoring registers from the stack after a VM-Exit in lieu of zeroing them could lead to speculative execution with the guest's values, e.g. if the stack accesses miss the L1 cache[1]. Zeroing XORs are dirt cheap, so just be ultra-paranoid. Note that the scratch register (currently RCX) used to save/restore the guest state is also zeroed as its host-defined value is loaded via the stack, just with a MOV instead of a POP. [1] https://patchwork.kernel.org/patch/10771539/#22441255 Fixes:0cb5b30698("kvm: vmx: Scrub hardware GPRs at VM-exit") Cc: Jim Mattson <jmattson@google.com> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> [bwh: Backported to 4.19: adjust filename, context] Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk> 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.
See Documentation/00-INDEX for a list of what is contained in each file.
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.