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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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c7d65a78fc
I've been informed by someone on LWN called 'slashdot' that some i386 machines do not support a true cmpxchg. The cmpxchg used by the i386 NMI nesting code must be a true cmpxchg as disabling interrupts will not work for NMIs (which is the work around for i386s that do not have a true cmpxchg). This 'slashdot' character also suggested a fix to the issue. As the state of the nesting NMIs goes as follows: NOT_RUNNING -> EXECUTING EXECUTING -> NOT_RUNNING EXECUTING -> LATCHED LATCHED -> EXECUTING Having these states as enum values of: NOT_RUNNING = 0 EXECUTING = 1 LATCHED = 2 Instead of a cmpxchg to make EXECUTING -> NOT_RUNNING a dec_and_test() would work as well. If the dec_and_test brings the state to NOT_RUNNING, that is the same as a cmpxchg succeeding to change EXECUTING to NOT_RUNNING. If a nested NMI were to come in and change it to LATCHED, the dec_and_test() would convert the state to EXECUTING (what we want it to be in such a case anyway). I asked 'slashdot' to post this as a patch, but it never came to be. I decided to do the work instead. Thanks to H. Peter Anvin for suggesting to use this_cpu_dec_and_return() instead of local_dec_and_test(&__get_cpu_var()). Link: http://lwn.net/Articles/484932/ Cc: H. Peter Anvin <hpa@zytor.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> |
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| boot | ||
| configs | ||
| crypto | ||
| ia32 | ||
| include/asm | ||
| kernel | ||
| kvm | ||
| lguest | ||
| lib | ||
| math-emu | ||
| mm | ||
| net | ||
| oprofile | ||
| pci | ||
| platform | ||
| power | ||
| realmode | ||
| syscalls | ||
| tools | ||
| um | ||
| vdso | ||
| video | ||
| xen | ||
| .gitignore | ||
| Kbuild | ||
| Kconfig | ||
| Kconfig.cpu | ||
| Kconfig.debug | ||
| Makefile | ||
| Makefile_32.cpu | ||
| Makefile.um | ||