Hi,
On Thu, 2009-04-09 at 12:32 +0200, Simon Holm Thøgersen wrote:> ons, 08 04 2009 kl. 17:58 -0300, skrev Matias Zabaljauregui:> > Simon, Patrick,> > > > On Wed, 2009-04-08 at 10:21 +0930, Rusty Russell wrote:> > > On Tuesday 07 April 2009 04:19:58 Matias Zabaljauregui wrote:> > > > But then, when it tries to re-execute the faulting instruction, which is> > > > now patched with "cd 1f 90" (int 0x1f, nop), it raises an invalid code> > > > fault again, instead of doing the trap. > > > > > > COW on the page? Perhaps try flushing all the shadow pagetables after a> > > rewrite?> > > > > > Rusty.> > > > Rusty suggested that perhaps we need to flush all shadow after rewriting. > > Could you please try this patch?> > Yes, it fixes the issue.
great, thanks for testing.
> > > > BTW, shouldn't this also affect my test boxes if this were the case?> > > Could be the timing differences between our boxes I guess?
I haven't read COW code, but I cannot figure out how CPU timingdifferences could affect a logic driven by faults. I will investigatefurther and let you know if I can yield any conclusion.
> > The compiler used seems to play a role as well, though. I compiled a> kernel on another box and using that there was no problems even without> the patch. If you are interested in testing the faulty kernel I could> make it available to you.> Simon
Regards,
Matias
> > > > diff --git a/drivers/lguest/x86/core.c b/drivers/lguest/x86/core.c> > index a6b7176..b4747f7 100644> > --- a/drivers/lguest/x86/core.c> > +++ b/drivers/lguest/x86/core.c> > @@ -324,6 +324,7 @@ static void rewrite_hypercall(struct lg_cpu *cpu)> > u8 insn[3] = {0xcd, 0x1f, 0x90};> > > > __lgwrite(cpu, guest_pa(cpu, cpu->regs->eip), insn, sizeof(insn));> > + guest_pagetable_clear_all(cpu);> > }> > > > static bool is_hypercall(struct lg_cpu *cpu)> >
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