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[14.202.190.183]) by smtp.gmail.com with ESMTPSA id i20sm10609622pfd.89.2020.03.25.07.29.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 Mar 2020 07:30:03 -0700 (PDT) From: Nicholas Piggin To: qemu-ppc@nongnu.org Subject: [PATCH v2 2/4] ppc/spapr: Improve FWNMI machine check delivery corner case comments Date: Thu, 26 Mar 2020 00:29:04 +1000 Message-Id: <20200325142906.221248-3-npiggin@gmail.com> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20200325142906.221248-1-npiggin@gmail.com> References: <20200325142906.221248-1-npiggin@gmail.com> MIME-Version: 1.0 X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2607:f8b0:4864:20::433 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Aravinda Prasad , Alexey Kardashevskiy , Mahesh Salgaonkar , qemu-devel@nongnu.org, Nicholas Piggin , Greg Kurz , =?utf-8?q?C=C3=A9dric_Le_Goater?= , Ganesh Goudar , David Gibson Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" 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 Signed-off-by: Nicholas Piggin --- 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"); }