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ppc/spapr: Improve FWNMI machine check delivery corner case comments

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Some of the conditions are not as clearly documented as they could be.
Also the non-FWNMI case does not need a large comment.

Reviewed-by: Greg Kurz <groug@kaod.org>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Message-Id: <20200325142906.221248-3-npiggin@gmail.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This commit is contained in:
Nicholas Piggin 2020-03-26 00:29:04 +10:00 committed by David Gibson
parent ec010c0066
commit 6c3dd24c05
1 changed files with 11 additions and 8 deletions
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19
hw/ppc/spapr_events.c
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@ -860,17 +860,13 @@ void spapr_mce_req_event(PowerPCCPU *cpu, bool recovered)
Error *local_err = NULL;
if (spapr->fwnmi_machine_check_addr == -1) {
/*
* This implies that we have hit a machine check either when the
* guest has not registered FWNMI (i.e., "ibm,nmi-register" not
* called) or between system reset and "ibm,nmi-register".
* Fall back to the old machine check behavior in such cases.
*/
/* Non-FWNMI case, deliver it like an architected CPU interrupt. */
cs->exception_index = POWERPC_EXCP_MCHECK;
ppc_cpu_do_interrupt(cs);
return;
}
/* Wait for FWNMI interlock. */
while (spapr->fwnmi_machine_check_interlock != -1) {
/*
* Check whether the same CPU got machine check error
@ -882,8 +878,13 @@ void spapr_mce_req_event(PowerPCCPU *cpu, bool recovered)
return;
}
qemu_cond_wait_iothread(&spapr->fwnmi_machine_check_interlock_cond);
/* Meanwhile if the system is reset, then just return */
if (spapr->fwnmi_machine_check_addr == -1) {
/*
* If the machine was reset while waiting for the interlock,
* abort the delivery. The machine check applies to a context
* that no longer exists, so it wouldn't make sense to deliver
* it now.
*/
return;
}
}
@ -894,7 +895,9 @@ void spapr_mce_req_event(PowerPCCPU *cpu, bool recovered)
* We don't want to abort so we let the migration to continue.
* In a rare case, the machine check handler will run on the target.
* Though this is not preferable, it is better than aborting
* the migration or killing the VM.
* the migration or killing the VM. It is okay to call
* migrate_del_blocker on a blocker that was not added (which the
* nmi-interlock handler would do when it's called after this).
*/
warn_report("Received a fwnmi while migration was in progress");
}