Messages in this thread | | | Date | Mon, 15 Jul 2019 10:24:21 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [RFC PATCH, x86]: Disable CPA cache flush for selfsnoop targets |
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Uros,
On Thu, 11 Jul 2019, Uros Bizjak wrote: > Recent patch [1] disabled a self-snoop feature on a list of processor > models with a known errata, so we are confident that the feature > should work on remaining models also for other purposes than to speed > up MTRR programming. > > I would like to resurrect an old patch [2] that avoids calling clflush > and wbinvd > to invalidate caches when CPU supports selfsnoop.
Please do not attach patches, send them inline and please add a proper changelog. Just saying 'Disable CPA cache flush for selfsnoop targets' in the subject line then nada gives absolutely zero information.
> The patch was ported to latest Fedora kernel (5.1.16) and tested with > CONFIG_CPA_DEBUG on INTEL_FAM6_IVYBRIDGE_X. The relevant ports of > dmesg show: > > ... > < hundreds of CPA protect messages, resulting from set_memory_rw CPA > undo test in mm/init_64.c > > CPA protect Rodata RO: 0xffffffffbd1fe000 - 0xffffffffbd1fefff PFN > 1461fe req 8000000000000063 prevent 0000000000000002 > CPA protect Rodata RO: 0xffff889c461fe000 - 0xffff889c461fefff PFN > 1461fe req 8000000000000063 prevent 0000000000000002 > Testing CPA: again > Freeing unused kernel image memory: 2016K > Freeing unused kernel image memory: 4K > x86/mm: Checked W+X mappings: passed, no W+X pages found. > rodata_test: all tests were successful > x86/mm: Checking user space page tables > x86/mm: Checked W+X mappings: passed, no W+X pages found. > > and from CPA selftest: > > CPA self-test: > 4k 36352 large 4021 gb 0 x 81[ffff889b00098000-ffff889bdf7ff000] miss 133120 > 4k 180224 large 3740 gb 0 x 81[ffff889b00098000-ffff889bdf7ff000] miss 133120 > 4k 180224 large 3740 gb 0 x 81[ffff889b00098000-ffff889bdf7ff000] miss 133120 > ok.
These outputs are pretty useless simply because the selftest only verifies the inner workings of CPA itself, but has nothing to do with the correctness vs. cache flushing.
Thanks,
tglx
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