Fork of alistair23 Linux kernel for reMarkable from https://github.com/alistair23/linux
4a267aa707
According to the ARM ARM, registers CNT{P,V}_TVAL_EL0 have bits [63:32]
RES0 [1]. When reading the register, the value is truncated to the least
significant 32 bits [2], and on writes, TimerValue is treated as a signed
32-bit integer [1, 2].
When the guest behaves correctly and writes 32-bit values, treating TVAL
as an unsigned 64 bit register works as expected. However, things start
to break down when the guest writes larger values, because
(u64)0x1_ffff_ffff = 8589934591. but (s32)0x1_ffff_ffff = -1, and the
former will cause the timer interrupt to be asserted in the future, but
the latter will cause it to be asserted now. Let's treat TVAL as a
signed 32-bit register on writes, to match the behaviour described in
the architecture, and the behaviour experimentally exhibited by the
virtual timer on a non-vhe host.
[1] Arm DDI 0487E.a, section D13.8.18
[2] Arm DDI 0487E.a, section D11.2.4
Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
[maz: replaced the read-side mask with lower_32_bits]
Signed-off-by: Marc Zyngier <maz@kernel.org>
Fixes:
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| Documentation | ||
| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
README
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.