Re: [kvm-devel] [PATCH] gfxboot VMX workaround v2

[Guillaume T. <gui...@ex...>]

On Fri, 18 Apr 2008 08:23:07 -0500
Anthony Liguori <an...@co...> wrote:

 
> This doesn't seem right.  You should have been able to break out of the 
> emulator long before encountering an out instruction.  The next 
> instruction you encounter should be a mov instruction.  Are you sure 
> you're updating eip correctly?

I think that eip is updated correctly but you're right, I think that
the condition to stop emulation is not well implemented. I emulate a
lot of mov instructions and I remain blocked in the emulation loop
until I reach the "out" instruction. The loop is the following:

  [...]
  cs_rpl = vmcs_read16(GUEST_CS_SELECTOR) & SELECTOR_RPL_MASK;
  ss_rpl = vmcs_read16(GUEST_SS_SELECTOR) & SELECTOR_RPL_MASK;

  while (cs_rpl != ss_rpl) {
      if (emulate_instruction(vcpu, NULL, 0,0, 0) == EMULATE_FAIL) {
          printk(KERN_INFO "%s: emulation of 0x%x failed\n",
                           __FUNCTION__,
                           vcpu->arch.emulate_ctxt.decode.b);
          return -1;
       }
       cs_rpl = vmcs_read16(GUEST_CS_SELECTOR) & SELECTOR_RPL_MASK;
       ss_rpl = vmcs_read16(GUEST_SS_SELECTOR) & SELECTOR_RPL_MASK;
  }
  printk(KERN_INFO "%s: VMX friendly state recovered\n", __FUNCTION__);
  // I never reach this point

Maybe CS and SS selector are not well updated. I will add trace to see
their values before and after the emulation.


Regards,
Guillaume