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Mon, 12 Dec 2022 23:01:56 GMT Received: from smtpav06.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 6B8B158060; Mon, 12 Dec 2022 23:01:56 +0000 (GMT) Received: from smtpav06.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 4525858055; Mon, 12 Dec 2022 23:01:56 +0000 (GMT) Received: from localhost (unknown [9.163.54.62]) by smtpav06.wdc07v.mail.ibm.com (Postfix) with ESMTP; Mon, 12 Dec 2022 23:01:56 +0000 (GMT) From: Nathan Lynch To: linuxppc-dev@lists.ozlabs.org Subject: [PATCH v2 4/4] powerpc/rtas: add tracepoints around RTAS entry Date: Mon, 12 Dec 2022 17:01:54 -0600 Message-Id: <20221212230154.851325-5-nathanl@linux.ibm.com> X-Mailer: git-send-email 2.37.3 In-Reply-To: <20221212230154.851325-1-nathanl@linux.ibm.com> References: <20221212230154.851325-1-nathanl@linux.ibm.com> MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-GUID: uT21HJhrb3RDKqmkeG4lIvc2E_ODAc7V X-Proofpoint-ORIG-GUID: QeAVTZsBHRbWx_S8NGHO5Qff33ycQ7q2 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.923,Hydra:6.0.545,FMLib:17.11.122.1 definitions=2022-12-12_02,2022-12-12_02,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 impostorscore=0 phishscore=0 adultscore=0 priorityscore=1501 spamscore=0 mlxlogscore=929 clxscore=1015 lowpriorityscore=0 bulkscore=0 suspectscore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2210170000 definitions=main-2212120199 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: tyreld@linux.ibm.com, nnac123@linux.ibm.com, ldufour@linux.ibm.com, ajd@linux.ibm.com, npiggin@gmail.com Errors-To: linuxppc-dev-bounces+incoming=patchwork.ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" Decompose the RTAS entry C code into tracing and non-tracing variants, calling the just-added tracepoints in the tracing-enabled path. Skip tracing in contexts known to be unsafe (real mode, CPU offline). Signed-off-by: Nathan Lynch --- arch/powerpc/kernel/rtas.c | 59 ++++++++++++++++++++++++++++++++++---- 1 file changed, 53 insertions(+), 6 deletions(-) diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c index 7a4c0505812b..1c53ef38d14e 100644 --- a/arch/powerpc/kernel/rtas.c +++ b/arch/powerpc/kernel/rtas.c @@ -38,6 +38,7 @@ #include #include #include +#include #include /** @@ -528,24 +529,70 @@ static const struct rtas_function *rtas_token_to_function(s32 token) /* This is here deliberately so it's only used in this file */ void enter_rtas(unsigned long); +static void __do_enter_rtas(struct rtas_args *args) +{ + enter_rtas(__pa(args)); + srr_regs_clobbered(); /* rtas uses SRRs, invalidate */ +} + +static void __do_enter_rtas_trace(struct rtas_args *args) +{ + const char *name = NULL; + /* + * If the tracepoints that consume the function name aren't + * active, avoid the lookup. + */ + if ((trace_rtas_input_enabled() || trace_rtas_output_enabled())) { + const s32 token = be32_to_cpu(args->token); + const struct rtas_function *func = rtas_token_to_function(token); + + name = func->name; + } + + trace_rtas_input(args, name); + trace_rtas_ll_entry(args); + + __do_enter_rtas(args); + + trace_rtas_ll_exit(args); + trace_rtas_output(args, name); +} + static void do_enter_rtas(struct rtas_args *args) { - unsigned long msr; - + const unsigned long msr = mfmsr(); + /* + * Situations where we want to skip any active tracepoints for + * safety reasons: + * + * 1. The last code executed on an offline CPU as it stops, + * i.e. we're about to call stop-self. The tracepoints' + * function name lookup uses xarray, which uses RCU, which + * isn't valid to call on an offline CPU. Any events + * emitted on an offline CPU will be discarded anyway. + * + * 2. In real mode, as when invoking ibm,nmi-interlock from + * the pseries MCE handler. We cannot count on trace + * buffers or the entries in rtas_token_to_function_xarray + * to be contained in the RMO. + */ + const unsigned long mask = MSR_IR | MSR_DR; + const bool can_trace = likely(cpu_online(raw_smp_processor_id()) && + (msr & mask) == mask); /* * Make sure MSR[RI] is currently enabled as it will be forced later * in enter_rtas. */ - msr = mfmsr(); BUG_ON(!(msr & MSR_RI)); BUG_ON(!irqs_disabled()); hard_irq_disable(); /* Ensure MSR[EE] is disabled on PPC64 */ - enter_rtas(__pa(args)); - - srr_regs_clobbered(); /* rtas uses SRRs, invalidate */ + if (can_trace) + __do_enter_rtas_trace(args); + else + __do_enter_rtas(args); } struct rtas_t rtas = {