[bug report] x86/sev: Split up runtime #VC handler for correct state tracking

[Dan Carpenter <dan.carpenter@oracle.com>]

Hello Joerg Roedel,

The patch be1a5408868a: "x86/sev: Split up runtime #VC handler for
correct state tracking" from Jun 18, 2021, leads to the following
static checker warning:

	arch/x86/kernel/kvm.c:153 kvm_async_pf_task_wait_schedule()
	warn: sleeping in atomic context

arch/x86/kernel/sev.c
  1416           * Handle #DB before calling into !noinstr code to avoid recursive #DB.
  1417           */
  1418          if (vc_is_db(error_code)) {
  1419                  exc_debug(regs);
  1420                  return;
  1421          }
  1422  
  1423          irq_state = irqentry_nmi_enter(regs);
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
preempt disabled inside irqentry_nmi_enter().

  1424  
  1425          instrumentation_begin();
  1426  
  1427          if (!vc_raw_handle_exception(regs, error_code)) {
                     ^^^^^^^^^^^^^^^^^^^^^^^^

These sleeping in atomic static checker warnings come with a lot of
caveats because the call tree is very long and it's easy to have false
positives.

--> vc_raw_handle_exception()
    --> vc_forward_exception()
        --> exc_page_fault()

Page faults always sleep right?

  1428                  /* Show some debug info */
  1429                  show_regs(regs);
  1430  
  1431                  /* Ask hypervisor to sev_es_terminate */
  1432                  sev_es_terminate(GHCB_SEV_ES_REASON_GENERAL_REQUEST);
  1433  
  1434                  /* If that fails and we get here - just panic */
  1435                  panic("Returned from Terminate-Request to Hypervisor\n");
  1436          }
  1437  
  1438          instrumentation_end();
  1439          irqentry_nmi_exit(regs, irq_state);
  1440  }

regards,
dan carpenter