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89c313f20c
Optimize the clearing of dirty state in TDP MMU SPTEs by doing an atomic-AND (on SPTEs that have volatile bits) instead of the full XCHG that currently ends up being invoked (see kvm_tdp_mmu_write_spte()). Clearing _only_ the bit in question will allow KVM to skip the many irrelevant checks in __handle_changed_spte() by avoiding any collateral damage due to the XCHG writing all SPTE bits, e.g. the XCHG could race with fast_page_fault() setting the W-bit and the CPU setting the D-bit, and thus incorrectly drop the CPU's D-bit update. Link: https://lore.kernel.org/all/Y9hXmz%2FnDOr1hQal@google.com Signed-off-by: Vipin Sharma <vipinsh@google.com> Reviewed-by: David Matlack <dmatlack@google.com> [sean: split the switch to atomic-AND to a separate patch] Link: https://lore.kernel.org/r/20230321220021.2119033-5-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 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.