>
> Subject: lguest: workaround cmpxchg8b_emu by ignoring cli in the guest.
>
> It's only used by cmpxchg8b_emu (see db677ffa5f5a for the gory
> details), and fixing that to be paravirt aware would be more work than
> simply ignoring it (and AFAICT only help lguest).
>
> (We can't emulate it properly: the popf which expects to restore interrupts
> does not trap).
>
> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
> Cc: Jeremy Fitzhardinge <jeremy@xensource.com>
> Cc:
virtualization@lists.osdl.org
>
> diff --git a/drivers/lguest/x86/core.c b/drivers/lguest/x86/core.c
> --- a/drivers/lguest/x86/core.c
> +++ b/drivers/lguest/x86/core.c
> @@ -288,6 +288,18 @@ static int emulate_insn(struct lg_cpu *c
> insn = lgread(cpu, physaddr, u8);
>
> /*
> + * Around 2.6.33, the kernel started using an emulation for the
> + * cmpxchg8b instruction in early boot on many configurations. This
> + * code isn't paravirtualized, and it tries to disable interrupts.
> + * Ignore it, which will Mostly Work.
> + */
> + if (insn == 0xfa) {
> + /* "cli", or Clear Interrupt Enable instruction. Skip it. */
> + cpu->regs->eip++;
> + return 1;
> + }
> +
> + /*
> * 0x66 is an "operand prefix". It means it's using the upper 16 bits
> * of the eax register.
> */
>
