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b41f8638b9
Rework KVM's processing of the PIR to use the same algorithm as posted
MSIs, i.e. to do READ(x4) => XCHG(x4) instead of (READ+XCHG)(x4). Given
KVM's long-standing, sub-optimal use of 32-bit accesses to the PIR, it's
safe to say far more thought and investigation was put into handling the
PIR for posted MSIs, i.e. there's no reason to assume KVM's existing
logic is meaningful, let alone superior.
Matching the processing done by posted MSIs will also allow deduplicating
the code between KVM and posted MSIs.
See the comment for handle_pending_pir() added by commit 1b03d82ba1
("x86/irq: Install posted MSI notification handler") for details on
why isolating loads from XCHG is desirable.
Suggested-by: Jim Mattson <jmattson@google.com>
Link: https://lore.kernel.org/r/20250401163447.846608-7-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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.