From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f178.google.com (mail-pl1-f178.google.com [209.85.214.178]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 22A7E3CF046 for ; Tue, 10 Mar 2026 16:46:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.178 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773161176; cv=none; b=gy8KaCzmXoj91LCcAL08YpY6LVZMhx4X7x0KSwwW8XRoljWmnkR+2NfdLFjMl1d9QzY4PNkxeQSF3LeFlYPiEUA5my2kcQFZjVnmM8Mt+C/A6qz16VqDE5mQKdAM1rKSHMXeMVDP1UT4OHBPgWuUG5FXnNrSrwI/UuBLn4WLiDg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773161176; c=relaxed/simple; bh=R/VezTFuRy+8dCiqKWzNcAEuYbrxxgqZyernvqhVsGQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=rf8d1pO8i6RaR3MnQA1C0EhqP0OzOzivtaRjw2WFhItdCi8P8J75th23vMdFKDXyKtAwQaWF0Z2iilbElCscrRAW2f5LdFHrCj+DZvK8Xbhcsw4PbjInb9eF84A9d+oKRRSI/QdOYlZyQw6ideRKRl2IMI+z97+dkAQvaMlNpvk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=kAXmdWOn; arc=none smtp.client-ip=209.85.214.178 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="kAXmdWOn" Received: by mail-pl1-f178.google.com with SMTP id d9443c01a7336-2ae3f822163so2605ad.0 for ; Tue, 10 Mar 2026 09:46:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1773161174; x=1773765974; darn=lists.linux.dev; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date:from:to :cc:subject:date:message-id:reply-to; bh=PhBHMQz2Xxv7MfAmXPun1VqA0Hi+0AdqM8NUP6BxeHU=; b=kAXmdWOnm2ud8GJyaUWnejH/mUH0ugYz9whCLHIfuydg3twtk9jYsSwpwPY7xKav/v WCVnMhpgridnZNt5ig1Y9+6CHOqZSKDJIFFpuFFBRvkJ7DVltwYsXdR4boQFs+fyZguD vWt/wrrQHiiEeqjWxP0grNH3mYQbuSorchPiCaPyDtD6xALbd6PaCwOy6oe70MpCAb9/ xmrTKeYxJIOYWig8aeylHwC1yobnTjEMGWwwqst/Tdd5c0mLAqzKZ0n6tV17/DyKNurt vW7y8z984Py3++0OcTsgqiAMwjZDE6IaothbdkIBWE0UaQ+ADJmk/w0uIlaIBuiQ8os1 mFAQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1773161174; x=1773765974; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=PhBHMQz2Xxv7MfAmXPun1VqA0Hi+0AdqM8NUP6BxeHU=; b=OW3MV+lueysmFIciCdZ/xgWe4V8wwMCX+k8zwkavcq+vNhJt0p3G3peLSa6+IeTvFh CRMFs/T9JGE172Vx/I/FfWAi1ISP5kQbUoQpHvThbrLavUKdjKDkBX4lvwv1z5bOkLez A23cTiZVBogBhOErv654c/PRLToGrTFbnb8r8W8ofm2Mw+HfOOMK19YCnQmizFXp6fGW hJm7idp9oQ0pergHrLF174xluCdmqmGHJD1EeLxb6tp3lHK/obEnyMOIcRUH1fipUdMt /TYVdWJbwxARCQGiCa/78oCZJXAuGjkY2CuKaz6bVRLt3IbCGGheUUbpsmraHWpOvXAR UFmw== X-Gm-Message-State: AOJu0YxfhcbeYMUGTcM5KoUhhJucqFt6zj2/CYWJX5FP2g5jL/uru4Hq Kf/ymh0Bas0YvYUHygu58eUZ5VwNTFlspt+LmNYuWzNyOmx2JRQUqde5U4LVHJDBMw== X-Gm-Gg: ATEYQzyi51KWzNd2i8P2yVwUO5tHQM2vOJboIj89HOWUWwCnxOwKeCdJf/x3+Zgkkq3 fRB0ze9nusrlVBxWuXgQ/h0uyFMnAD+4XuZXTn0dRBW/EDl7Z55nSem7VZC+DrJO4BnpVb+A0O1 CYypv39pTMp+V2l/bA6ML29eYyIX1zIsZZwy+ywQcd1ROpqTu+NNktaRyoO5SzOGukEbQLnZ7xU UcupnECOwt4didhm767XTJsgNs5OJSLtDReNGwLbVNtD6GMswjqpbEK2/aMIpq1a+3iR8ck+vly w5TQbf8B9fVV92cvv+EPgGRm+yI8siQa8OwKUELEyKNsrMZyvdA4SZXBmNV3SAeX3paItGXLPIz JSBBhRwQZenk/FBV+YqXlwD8YC00mY1uwtTMK5XMoynpU7I52zr3dCRjjjLESgBv4591TEzZn1s 0GagvhE/i9Q13fTMZ9WHps4Kt8HZ/jQNt6DNI3tl3Di4PnrQKju6n3+RW7Og== X-Received: by 2002:a17:902:e80e:b0:2ae:7d03:c911 with SMTP id d9443c01a7336-2aea44c6cb9mr1860475ad.1.1773161173671; Tue, 10 Mar 2026 09:46:13 -0700 (PDT) Received: from google.com (10.129.124.34.bc.googleusercontent.com. [34.124.129.10]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-829a48a20c0sm17181205b3a.43.2026.03.10.09.46.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 10 Mar 2026 09:46:12 -0700 (PDT) Date: Tue, 10 Mar 2026 16:46:08 +0000 From: Pranjal Shrivastava To: Daniel Mentz Cc: iommu@lists.linux.dev, Will Deacon , Joerg Roedel , Robin Murphy , Jason Gunthorpe , Mostafa Saleh , Nicolin Chen , Ashish Mhetre , Sairaj Kodilkar Subject: Re: [PATCH v5 06/10] iommu/arm-smmu-v3: Add a usage counter for cmdq Message-ID: References: <20260126151157.3418145-1-praan@google.com> <20260126151157.3418145-7-praan@google.com> Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Mon, Mar 09, 2026 at 03:56:03PM -0700, Daniel Mentz wrote: > On Mon, Mar 9, 2026 at 2:13 PM Pranjal Shrivastava wrote: > > Still thinking out loud, but maybe we can have something like: > > > > if (owner) { > > .... > > > > if (atomic_inc_not_zero(&smmu->nr_cmdq_users)) { > > writel_relaxes(llq.prod, cmdq->q.prod_reg); > > has_ref = true; > > } else { > > > > /* SMMU is suspended, fake a consumption */ > > WRITE_ONCE(cmdq->q.llq.cons, prod); > > > > /* Avoid racing with resume */ > > sync = false; > > } > > > > atomic_set_release(&cmdq->owner_prod, prod); > > } > > > > if (sync) { > > > > ... same stuff .. > > > > } > > > > LMK, what you think? > > You'd need to make sure to cover the ARM_SMMU_OPT_MSIPOLL case: The > function __arm_smmu_cmdq_poll_until_msi() doesn't read > cmdq->q.llq.cons but rather waits for the MSI write into the command > queue. why? The goal is we don't poll at all, simply setting sync = false if the users == 0, we simply fake a consumption and move on. Thanks, Praan