Messages in this thread |  | | Date | Wed, 19 May 2021 19:54:50 +0200 | | From | Peter Zijlstra <> | | Subject | Re: [PATCH v2 5/8] x86/sev-es: Leave NMI-mode before sending signals |
| |
On Wed, May 19, 2021 at 03:52:48PM +0200, Joerg Roedel wrote: > --- a/arch/x86/kernel/sev.c > +++ b/arch/x86/kernel/sev.c > @@ -1343,9 +1343,10 @@ DEFINE_IDTENTRY_VC_SAFE_STACK(exc_vmm_communication) > return; > } > > + instrumentation_begin(); > + > irq_state = irqentry_nmi_enter(regs); > lockdep_assert_irqs_disabled(); > - instrumentation_begin(); > > /* > * This is invoked through an interrupt gate, so IRQs are disabled. The
That's just plain wrong. No instrumentation is allowed before you enter the exception context.
> @@ -1395,13 +1396,19 @@ DEFINE_IDTENTRY_VC_SAFE_STACK(exc_vmm_communication) > BUG(); > } > > -out: > - instrumentation_end(); > irqentry_nmi_exit(regs, irq_state); > + instrumentation_end();
And this can't be right either, same issue, no instrumentation is allowed after you leave the exception context.
> > return; > > fail: > + /* > + * Leave NMI mode - the GHCB is not busy anymore and depending on where > + * the #VC came from this code is about to either kill the task (when in > + * task context) or kill the machine. > + */ > + irqentry_nmi_exit(regs, irq_state); > +
And this is wrong too; because at this point the handler doesn't run in _any_ context anymore, certainly not one you can call regular C code from.
> if (user_mode(regs)) { > /* > * Do not kill the machine if user-space triggered the > @@ -1423,7 +1430,9 @@ DEFINE_IDTENTRY_VC_SAFE_STACK(exc_vmm_communication) > panic("Returned from Terminate-Request to Hypervisor\n"); > } > > - goto out; > + instrumentation_end(); > + > + return; > }
You either get to do what MCE does, or what MCE does. That is, either use task_work or MCE_USER and have the _user() handler use irqentry_enter_from_user_mode().
The above is an absolute no-go.
|  |