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909b583f81
Gavin reports of soft lockups on his Ampere Altra Max machine when backing KVM guests with hugetlb pages. Upon further investigation, it was found that the system is unable to keep up with parallel I-cache invalidations done by KVM's stage-2 fault handler. This is ultimately an implementation problem. I-cache maintenance instructions are available at EL0, so nothing stops a malicious userspace from hammering a system with CMOs and cause it to fall over. "Fixing" this problem in KVM is nothing more than slapping a bandage over a much deeper problem. Anyway, the kernel already has a heuristic for limiting TLB invalidations to avoid soft lockups. Reuse that logic to limit I-cache CMOs done by KVM to map executable pages on systems without FEAT_DIC. While at it, restructure __invalidate_icache_guest_page() to improve readability and squeeze our new condition into the existing branching structure. Link: https://lore.kernel.org/kvmarm/20230904072826.1468907-1-gshan@redhat.com/ Reviewed-by: Gavin Shan <gshan@redhat.com> Tested-by: Gavin Shan <gshan@redhat.com> Link: https://lore.kernel.org/r/20230920080133.944717-3-oliver.upton@linux.dev Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
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.