On Sat, Jan 31, 2015 at 12:31:42AM +0100, Borislav Petkov wrote: > asm volatile(ALTERNATIVE(ASM_NOP3, "clflush %[p]", > X86_BUG_CLFLUSH_MONITOR) > : [p] "+m" (*mwait_ptr)); > > Totally untested though - it is supposed to show the idea only.
Yeah, here's a working diff, ontop of this patchset: https://lkml.kernel.org/r/1422987390-17878-1-git-send-email...@alien8.de --- diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 6d7022c683e3..771ebd6e8b77 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -1432,7 +1432,11 @@ static inline void mwait_play_dead(void) * case where we return around the loop. */ mb(); - clflush(mwait_ptr); + + asm volatile(ALTERNATIVE("", "clflush %[p]", + X86_BUG_CLFLUSH_MONITOR) + : [p] "+m" (*(unsigned long *)mwait_ptr)); + mb(); __monitor(mwait_ptr, 0, 0); mb(); -- At build time you have: -- ... ffffffff81038dcc: 65 48 8b 1c 25 88 ab mov %gs:0xab88,%rbx # movq %gs:kernel_stack,%rbx #, pfo_ret__ ffffffff81038dd3: 00 00 ffffffff81038dd5: 48 81 eb c8 3f 00 00 sub $0x3fc8,%rbx # subq $16328, %rbx #, mwait_ptr ffffffff81038ddc: 0f 09 wbinvd ffffffff81038dde: 45 31 e4 xor %r12d,%r12d ffffffff81038de1: 0f 1f 80 00 00 00 00 nopl 0x0(%rax) ffffffff81038de8: 0f ae f0 mfence ffffffff81038deb: 90 nop ffffffff81038dec: 90 nop ffffffff81038ded: 90 nop ffffffff81038dee: 0f ae f0 mfence ffffffff81038df1: 48 89 d8 mov %rbx,%rax ... -- which during runtime, on those affected machines only, gets patched to: --- ... ffffffff81038dcc: mov %gs:0xab88,%rbx ffffffff81038dd5: sub $0x3fc8,%rbx ffffffff81038ddc: wbinvd ffffffff81038dde: xor %r12d,%r12d ffffffff81038de1: nopl 0x0(%rax) ffffffff81038de8: mfence ffffffff81038deb: clflush (%rbx) <--- ffffffff81038dee: mfence ffffffff81038df1: mov %rbx,%rax ... --- :-) -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
