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cae7395183
Commitf7c90c2aa4("x86/xen: don't write ptes directly in 32-bit PV guests") needlessly (and heavily) penalized 64-bit guests here: The majority of the early page table updates is to writable pages (which get converted to r/o only after all the writes are done), in particular those involved in building the direct map (which consists of all 4k mappings in PV). On my test system this accounts for almost 16 million hypercalls when each could simply have been a plain memory write. Switch back to using native_set_pte(), except for updates of early ioremap tables (where a suitable accessor exists to recognize them). With 32-bit PV support gone, this doesn't need to be further conditionalized (albeit backports thereof may need adjustment). To avoid a fair number (almost 256k on my test system) of trap-and- emulate cases appearing as a result, switch the hook in xen_pagetable_init(). Finally commitd6b186c1e2("x86/xen: avoid m2p lookup when setting early page table entries") inserted a function ahead of xen_set_pte_init(), separating it from its comment (which may have been part of the reason why the performance regression wasn't anticipated / recognized while codeing / reviewing the change mentioned further up). Move the function up and adjust that comment to describe the new behavior. Signed-off-by: Jan Beulich <jbeulich@suse.com> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> Link: https://lore.kernel.org/r/57ce1289-0297-e96e-79e1-cedafb5d9bf6@suse.com Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.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.