From: David Gibson <david@gibson.dropbear.id.au>
To: Nicholas Piggin <npiggin@gmail.com>
Cc: "Aravinda Prasad" <arawinda.p@gmail.com>,
"Alexey Kardashevskiy" <aik@ozlabs.ru>,
"Mahesh Salgaonkar" <mahesh@linux.vnet.ibm.com>,
qemu-devel@nongnu.org, "Greg Kurz" <groug@kaod.org>,
"Cédric Le Goater" <clg@fr.ibm.com>,
"Ganesh Goudar" <ganeshgr@linux.ibm.com>,
qemu-ppc@nongnu.org
Subject: Re: [PATCH v2 2/4] ppc/spapr: Improve FWNMI machine check delivery corner case comments
Date: Thu, 26 Mar 2020 11:18:25 +1100 [thread overview]
Message-ID: <20200326001825.GN36889@umbus.fritz.box> (raw)
In-Reply-To: <20200325142906.221248-3-npiggin@gmail.com>
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On Thu, Mar 26, 2020 at 12:29:04AM +1000, Nicholas Piggin wrote:
> 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>
Applied to ppc-for-5.0.
> ---
> hw/ppc/spapr_events.c | 19 +++++++++++--------
> 1 file changed, 11 insertions(+), 8 deletions(-)
>
> diff --git a/hw/ppc/spapr_events.c b/hw/ppc/spapr_events.c
> index a4a540f43d..a908c5d0e9 100644
> --- a/hw/ppc/spapr_events.c
> +++ b/hw/ppc/spapr_events.c
> @@ -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");
> }
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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next prev parent reply other threads:[~2020-03-26 0:43 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-25 14:29 [PATCH v2 0/4] FWNMI follow up patches Nicholas Piggin
2020-03-25 14:29 ` [PATCH v2 1/4] ppc/spapr: KVM FWNMI should not be enabled until guest requests it Nicholas Piggin
2020-03-25 17:17 ` Greg Kurz
2020-03-26 0:17 ` David Gibson
2020-03-25 14:29 ` [PATCH v2 2/4] ppc/spapr: Improve FWNMI machine check delivery corner case comments Nicholas Piggin
2020-03-26 0:18 ` David Gibson [this message]
2020-03-25 14:29 ` [PATCH v2 3/4] ppc/spapr: Add FWNMI machine check delivery warnings Nicholas Piggin
2020-03-25 17:24 ` Greg Kurz
2020-03-26 0:19 ` David Gibson
2020-03-25 14:29 ` [PATCH v2 4/4] ppc/spapr: Don't kill the guest if a recovered FWNMI machine check delivery fails Nicholas Piggin
2020-03-25 18:13 ` Greg Kurz
2020-03-26 0:30 ` David Gibson
2020-03-26 0:30 ` David Gibson
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