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Tue, 10 Nov 2026 07:33:11 -0800 (PST) Received: from [192.168.1.3] ([37.18.141.193]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4ba02387ed4sm47355825e9.4.2026.11.10.07.33.09 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 10 Nov 2026 07:33:10 -0800 (PST) Message-ID: <144477e4-e0f9-4c9c-94de-136c459e99a0@linaro.org> Date: Tue, 10 Nov 2026 15:33:09 +0000 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 14/23] coresight: trbe: Treat access not allowed stops as fatal To: Leo Yan Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, coresight@lists.linaro.org, Suzuki K Poulose , Mike Leach , Alexander Shishkin , Anshuman Khandual , Tamas Petz , Tamas Zsoldos , Suyash Mahar , Amir Ayupov References: <20261016-trbe_enable_disable_irq_handle_refactor-v2-0-3f57cf3199b1@arm.com> <20261016-trbe_enable_disable_irq_handle_refactor-v2-14-3f57cf3199b1@arm.com> Content-Language: en-US From: James Clark In-Reply-To: <20261016-trbe_enable_disable_irq_handle_refactor-v2-14-3f57cf3199b1@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 16/10/2026 17:55, Leo Yan wrote: > Arm ARM (ARM DDI 0487 M.b), the rule R_RRCNN in "D6.11 UNPREDICTABLE > behavior" permits a buffer management event when the effective SCR_EL3 > security state does not match the owning Security state. This can stop > collection with IRQ=1, S=1, EC=0 and BSC=0 while leaving the other > status fields unchanged. > > With EA and WRAP clear, trbe_get_fault_act() currently returns SPURIOUS > for this status. The spurious handler re-enables TRBE without clearing > S, so collection can remain stopped. A retained WRAP indication can > instead cause the status to be treated as a normal buffer wrap. > > Recognize this architecturally permitted stopped status as an access > not allowed error and return FATAL so the fatal handling reports > truncated trace. Check the syndrome before WRAP and do not exclude > TRG, since both fields are left unchanged by this stop. Check the saved > IRQ bit to preserve updates without a pending interrupt. > > Signed-off-by: Leo Yan > --- > drivers/hwtracing/coresight/coresight-trbe.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/drivers/hwtracing/coresight/coresight-trbe.c b/drivers/hwtracing/coresight/coresight-trbe.c > index 4aeed1a17c4bf1653fb41731ac15f31feec7ed2e..1c585b6123df2f20d08747678d836742ce9564cc 100644 > --- a/drivers/hwtracing/coresight/coresight-trbe.c > +++ b/drivers/hwtracing/coresight/coresight-trbe.c > @@ -708,6 +708,14 @@ static enum trbe_fault_action trbe_get_fault_act(struct perf_output_handle *hand > goto out_fatal; > } > > + /* An access not allowed stop can leave WRAP and TRG unchanged. */ > + if (is_trbe_irq(trbsr) && !is_trbe_running(trbsr) && > + ec == TRBSR_EL1_EC_OTHER && > + bsc == TRBSR_EL1_BSC_NOT_STOPPED) { > + err_str = "Trace buffer access not allowed"; > + goto out_fatal; > + } > + > if (is_trbe_wrap(trbsr)) > return TRBE_FAULT_ACT_WRAP; > > Reviewed-by: James Clark