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b0b6e86846
cpu_llc_id (Last Level Cache ID) derivation on AMD Fam17h has an
underflow bug when extracting the socket_id value. It starts from 0
so subtracting 1 from it will result in an invalid value. This breaks
scheduling topology later on since the cpu_llc_id will be incorrect.
For example, the the cpu_llc_id of the *other* CPU in the loops in
set_cpu_sibling_map() underflows and we're generating the funniest
thread_siblings masks and then when I run 8 threads of nbench, they get
spread around the LLC domains in a very strange pattern which doesn't
give you the normal scheduling spread one would expect for performance.
Other things like EDAC use cpu_llc_id so they will be b0rked too.
So, the APIC ID is preset in APICx020 for bits 3 and above: they contain
the core complex, node and socket IDs.
The LLC is at the core complex level so we can find a unique cpu_llc_id
by right shifting the APICID by 3 because then the least significant bit
will be the Core Complex ID.
Tested-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Yazen Ghannam <Yazen.Ghannam@amd.com>
[ Cleaned up and extended the commit message. ]
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: <stable@vger.kernel.org> # v4.4..
Cc: Aravind Gopalakrishnan <aravindksg.lkml@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Fixes:
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| arm | ||
| arm64 | ||
| avr32 | ||
| blackfin | ||
| c6x | ||
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| h8300 | ||
| hexagon | ||
| ia64 | ||
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| mn10300 | ||
| nios2 | ||
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| s390 | ||
| score | ||
| sh | ||
| sparc | ||
| tile | ||
| um | ||
| unicore32 | ||
| x86 | ||
| xtensa | ||
| .gitignore | ||
| Kconfig | ||