On Mon, Feb 24, 2014 at 02:13:29PM -0500, Steven Rostedt wrote:
> Ah, and x86_64 saves off the cr2 register when entering NMI and restores
> it before returning. But it seems to be missing from the i386 code.
arch/x86/kernel/nmi.c:
#define nmi_nesting_preprocess(regs) \
do { \
if (this_cpu_read(nmi_state) != NMI_NOT_RUNNING) { \
this_cpu_write(nmi_state, NMI_LATCHED); \
return; \
} \
this_cpu_write(nmi_state, NMI_EXECUTING); \
this_cpu_write(nmi_cr2, read_cr2()); \
} while (0); \
nmi_restart:
#define nmi_nesting_postprocess() \
do { \
if (unlikely(this_cpu_read(nmi_cr2) != read_cr2())) \
write_cr2(this_cpu_read(nmi_cr2)); \
if (this_cpu_dec_return(nmi_state)) \
goto nmi_restart; \
} while (0)
That very much looks like saving/restoring CR2 to me.
FWIW; I hate how the x86_64 and i386 versions of this NMI nesting magic
are so completely different.
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