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Wed, 13 May 2026 07:50:01 -0700 (PDT) Received: from google.com ([118.150.148.19]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-368edf54a55sm3252602a91.9.2026.05.13.07.49.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 13 May 2026 07:50:00 -0700 (PDT) Date: Wed, 13 May 2026 22:49:55 +0800 From: Kuan-Wei Chiu To: Alistair Francis Cc: pbonzini@redhat.com, marcandre.lureau@redhat.com, palmer@dabbelt.com, alistair.francis@wdc.com, christoph.muellner@vrull.eu, liwei1518@gmail.com, daniel.barboza@oss.qualcomm.com, zhiwei_liu@linux.alibaba.com, chao.liu.zevorn@gmail.com, jserv@ccns.ncku.edu.tw, eleanor15x@gmail.com, qemu-devel@nongnu.org, qemu-riscv@nongnu.org Subject: Re: [PATCH RFC 1/5] target/riscv: Add stubs for T-Head PMU CSRs Message-ID: References: <20260512094614.3464388-1-visitorckw@gmail.com> <20260512094614.3464388-2-visitorckw@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Received-SPF: pass client-ip=2607:f8b0:4864:20::1035; envelope-from=visitorckw@gmail.com; helo=mail-pj1-x1035.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Wed, May 13, 2026 at 12:13:25PM +1000, Alistair Francis wrote: > On Tue, May 12, 2026 at 7:47 PM Kuan-Wei Chiu wrote: > > > > T-Head CPUs use custom CSRs for performance monitoring, specifically > > mcounterinten (0x7ca) and mcounterof (0x7cb). > > > > Since we don't implement these custom PMU registers yet, the system > > crashes with an illegal instruction trap when OpenSBI like this: > > > > system_opcode_insn: Failed to access CSR 0x7ca from M-mode > > sbi_trap_error: hart0: trap1: illegal instruction handler failed (error -1) > > > > Add simple read/write stubs for these two CSRs. By silently ignoring > > writes and returning 0 on reads, we prevent the fatal exceptions and > > allow to continue normally. > > Can you include a link to the documentation for the CSRs > Sure. I'll add the link in v2. Regards, Kuan-Wei