Shameer Kolothum 980c41f554 KVM: arm64: Make the exposed feature bits in AA64DFR0_EL1 writable from userspace
KVM exposes the OS double lock feature bit to Guests but returns
RAZ/WI on Guest OSDLR_EL1 access. This breaks Guest migration between
systems where this feature differ. Add support to make this feature
writable from userspace by setting the mask bit. While at it, set the
mask bits for the exposed WRPs(Number of Watchpoints) as well.
Also update the selftest to cover these fields.

However we still can't make BRPs and CTX_CMPs fields writable, because
as per ARM ARM DDI 0487K.a, section D2.8.3 Breakpoint types and
linking of breakpoints, highest numbered breakpoints(BRPs) must be
context aware breakpoints(CTX_CMPs). KVM does not trap + emulate the
breakpoint registers, and as such cannot support a layout that misaligns
with the underlying hardware.

Reviewed-by: Oliver Upton <oliver.upton@linux.dev>
Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
Link: https://lore.kernel.org/r/20240816132819.34316-1-shameerali.kolothum.thodi@huawei.com
Signed-off-by: Marc Zyngier <maz@kernel.org>
2024-08-22 18:05:37 +01:00
2022-09-28 09:02:20 +02:00
2024-08-11 14:27:14 -07:00
2024-03-18 03:36:32 -06:00

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.
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