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[82.57.177.142]) by smtp.gmail.com with ESMTPSA id r23-20020a17090638d700b0099bc8db97bcsm477089ejd.131.2023.08.03.17.17.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 03 Aug 2023 17:17:03 -0700 (PDT) Date: Fri, 4 Aug 2023 02:16:59 +0200 From: Andrea Parri To: Mathieu Desnoyers Cc: paulmck@kernel.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, mmaas@google.com, hboehm@google.com, striker@us.ibm.com Subject: Re: [RFC PATCH] membarrier: riscv: Provide core serializing command Message-ID: References: <20230803040111.5101-1-parri.andrea@gmail.com> <4bf79f06-4593-134a-04dd-b8f89e96a1b8@efficios.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <4bf79f06-4593-134a-04dd-b8f89e96a1b8@efficios.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230803_171715_665894_AB25D306 X-CRM114-Status: UNSURE ( 8.43 ) X-CRM114-Notice: Please train this message. X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org > Can you double-check that riscv switch_mm() implies a fence.i or equivalent > on the CPU doing the switch_mm ? AFAICT, (riscv) switch_mm() does not guarantee that. > AFAIR membarrier use of sync_core_before_usermode relies on switch_mm > issuing a core serializing instruction. I see. Thanks for the clarification. BTW, the comment in __schedule() suggests that membarrier also relies on switch_mm() issuing a full memory barrier: I don't think this holds. Removing the "deferred icache flush" logic in switch_mm() - in favour of a "plain" MB; FENCE.I - would meet both of these requirements. Other ideas? Andrea _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv