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Mon, 15 Jun 2026 05:24:05 -0700 (PDT) Received: from draig.lan ([185.124.0.195]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-492203d2449sm234758625e9.14.2026.06.15.05.24.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 15 Jun 2026 05:24:04 -0700 (PDT) Received: from draig (localhost [IPv6:::1]) by draig.lan (Postfix) with ESMTP id E6C8C5F857; Mon, 15 Jun 2026 13:24:03 +0100 (BST) From: =?utf-8?Q?Alex_Benn=C3=A9e?= To: Peter Maydell Cc: qemu-devel@nongnu.org, Paolo Bonzini , Alexander Graf , Mohamed Mediouni , Pedro Barbuda , qemu-arm@nongnu.org, kvm@vger.kernel.org, Richard Henderson Subject: Re: [PATCH v7 7/8] target/arm: handle the WFE trap case In-Reply-To: (Peter Maydell's message of "Mon, 15 Jun 2026 12:01:56 +0100") References: <20260529082948.363931-1-alex.bennee@linaro.org> <20260529082948.363931-8-alex.bennee@linaro.org> <878q8gjcms.fsf@draig.linaro.org> User-Agent: mu4e 1.14.2-pre1; emacs 30.1 Date: Mon, 15 Jun 2026 13:24:03 +0100 Message-ID: <87wlw0htzw.fsf@draig.linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=2a00:1450:4864:20::32d; envelope-from=alex.bennee@linaro.org; helo=mail-wm1-x32d.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, 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-arm@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-arm-bounces+qemu-arm=archiver.kernel.org@nongnu.org Sender: qemu-arm-bounces+qemu-arm=archiver.kernel.org@nongnu.org Peter Maydell writes: > On Mon, 15 Jun 2026 at 11:56, Alex Benn=C3=A9e w= rote: >> >> Peter Maydell writes: >> >> > On Fri, 29 May 2026 at 09:29, Alex Benn=C3=A9e wrote: >> >> >> >> Now WFE can actually suspend on A-profile we also need to handle when >> >> its trapped. To do this we need to pass the instruction size so we can >> >> deal with the is_16bit syndrome encoding. >> >> >> >> Reviewed-by: Richard Henderson >> >> Signed-off-by: Alex Benn=C3=A9e >> > >> > Doesn't this need to go earlier in the patchset? Otherwise there's >> > a point where WFE can go to sleep but doesn't honour the trap bit. >> >> Hmm - the way I read the description was we would only trap if we were >> going to sleep. Pre 6/8 we never sleep so we can't trap. > > Yes, that's the point. The guarantee we have to uphold with > the trap bits is "if the WFE would actually go to sleep, then > we need to take the trap". > > - before this patchset: we never sleep, so never need to trap > - after patch 6: we can sleep, but we incorrectly won't trap > - after this patch: we can sleep and will trap > > So there's a window in this patchseries (after 6 but before 7) > where we don't do the right thing. OK I'll squash the two patches together. > > -- PMM --=20 Alex Benn=C3=A9e Virtualisation Tech Lead @ Linaro