7121c0f813
commit 2a5f1b67ec577fb1544b563086e0377f095f88e2 upstream.
We reset the guest's view of PMCR_EL0 unconditionally, based on
the host's view of this register. It is however legal for an
implementation not to provide any PMU, resulting in an UNDEF.
The obvious fix is to skip the reset of this shadow register
when no PMU is available, sidestepping the issue entirely.
If no PMU is available, the guest is not able to request
a virtual PMU anyway, so not doing nothing is the right thing
to do!
It is unlikely that this bug can hit any HW implementation
though, as they all provide a PMU. It has been found using nested
virt with the host KVM not implementing the PMU itself.
Fixes: ab9468340d2bc ("arm64: KVM: Add access handler for PMCR register")
Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20201210083059.1277162-1-maz@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
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In order to build the documentation, use ``make htmldocs`` or
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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.