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Marc Zyngier 0bc9a9e85f KVM: arm64: Work around x1e's CNTVOFF_EL2 bogosity
It appears that on Qualcomm's x1e CPU, CNTVOFF_EL2 doesn't really
work, specially with HCR_EL2.E2H=1.

A non-zero offset results in a screaming virtual timer interrupt,
to the tune of a few 100k interrupts per second on a 4 vcpu VM.
This is also evidenced by this CPU's inability to correctly run
any of the timer selftests.

The only case this doesn't break is when this register is set to 0,
which breaks VM migration.

When HCR_EL2.E2H=0, the timer seems to behave normally, and does
not result in an interrupt storm.

As a workaround, use the fact that this CPU implements FEAT_ECV,
and trap all accesses to the virtual timer and counter, keeping
CNTVOFF_EL2 set to zero, and emulate accesses to CVAL/TVAL/CTL
and the counter itself, fixing up the timer to account for the
missing offset.

And if you think this is disgusting, you'd probably be right.

Acked-by: Oliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20241217142321.763801-12-maz@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>
2025-01-02 19:19:10 +00:00
arch KVM: arm64: Work around x1e's CNTVOFF_EL2 bogosity 2025-01-02 19:19:10 +00:00
block block-6.13-20242901 2024-11-30 15:47:29 -08:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto Random number generator updates for Linux 6.13-rc1. 2024-11-19 10:43:44 -08:00
Documentation - Move the ->select callback to the correct ops structure in irq-mvebu-sei to 2024-12-01 12:37:58 -08:00
drivers i2c-for-6.13-rc1-part3 2024-12-01 13:38:24 -08:00
fs This pull request contains the following changes for UML: 2024-11-30 10:34:54 -08:00
include KVM: arm64: Work around x1e's CNTVOFF_EL2 bogosity 2025-01-02 19:19:10 +00:00
init - The series "resource: A couple of cleanups" from Andy Shevchenko 2024-11-25 16:09:48 -08:00
io_uring io_uring-6.13-20242901 2024-11-30 15:43:02 -08:00
ipc - The series "resource: A couple of cleanups" from Andy Shevchenko 2024-11-25 16:09:48 -08:00
kernel - Fix a case where posix timers with a thread-group-wide target would miss 2024-12-01 12:41:21 -08:00
lib vsnprintf: Removal of bprintf() 2024-12-01 13:10:51 -08:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm Kbuild updates for v6.13 2024-11-30 13:41:50 -08:00
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.get_maintainer.ignore MAINTAINERS: Retire Ralf Baechle 2024-11-12 15:48:59 +01:00
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README README: Fix spelling 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.