> My speculation is, that the asm is not removed but rather that regs.eax > isn't reloaded after the asm because the memory clobber doesn't clobber > automatic variables.
Yes that makes sense. I wasn't able to verify it so far though. Maybe the original poster could try the obvious patch instead of the volatile change. i8k: tell gcc that regs gets clobbered Signed-off-by: Andi Kleen <a...@linux.intel.com> diff --git a/drivers/char/i8k.c b/drivers/char/i8k.c index 3bc0eef..f3bbf73 100644 --- a/drivers/char/i8k.c +++ b/drivers/char/i8k.c @@ -142,7 +142,7 @@ static int i8k_smm(struct smm_regs *regs) "lahf\n\t" "shrl $8,%%eax\n\t" "andl $1,%%eax\n" - :"=a"(rc) + :"=a"(rc), "=m" (*regs) : "a"(regs) : "%ebx", "%ecx", "%edx", "%esi", "%edi", "memory"); #else @@ -167,7 +167,7 @@ static int i8k_smm(struct smm_regs *regs) "movl %%edx,0(%%eax)\n\t" "lahf\n\t" "shrl $8,%%eax\n\t" - "andl $1,%%eax\n":"=a"(rc) + "andl $1,%%eax\n":"=a"(rc), "=m" (*regs) : "a"(regs) : "%ebx", "%ecx", "%edx", "%esi", "%edi", "memory"); #endif -Andi