From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f197.google.com (mail-pf1-f197.google.com [209.85.210.197]) (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 7737D5947F2 for ; Tue, 8 Sep 2026 17:17:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.197 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788887861; cv=none; b=gJKrDXBFYgtvvAyvKnMhXBVKRf7wtEdAFi50KroBlWR3mNNCf6TA99GQet6+bwS5zam1r6AxWJRqk9RzfDeZmGOjgZMO8i0wjdAMumLTnfsLAb81tcxtFBZYmAd39bEzJZT+pMntjTm5ffNrGjtObbFYadqdM396bAcRd9pbv1M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788887861; c=relaxed/simple; bh=3ks5V6Ofdruc8FIg084YSeYPdHUEOsTEhfR4gWyXmvs=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=XmtohCY2BWOFGzGF5CGSLEN1aLgLwCZ+rgB3dbTKN9j/RggJfUw/DoQCh/KbF7JLeLFqedbEz9XxDq4tr3ZMZju/tT6WiDFEJ0f4vGXml3cvW9oxPcWW8hcUFabmogNJJqM59LGfnsCsXVjoHh3wkX1dPgMFkKbaiYFPXc/cQO8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--praan.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=TPopIQiK; arc=none smtp.client-ip=209.85.210.197 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=flex--praan.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="TPopIQiK" Received: by mail-pf1-f197.google.com with SMTP id d2e1a72fcca58-8485d853b08so6368225b3a.1 for ; Tue, 08 Sep 2026 10:17:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1788887859; x=1789492659; darn=lists.linux.dev; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:from:to:cc:subject:date:message-id:reply-to :content-type; bh=J/jv1ovVCNeCubLupVeuht7eNIRLVbkvYJqOaymhU6s=; b=TPopIQiKw4+R/tamrO9iwugtO2a5oQuf6W0LGA89Va5JmZ6sYL4tOaiGhByk3QmW7k GDXDMGiBSYaoP7ms3BD4fpJvhQSLZig7i6WDTY4CUzTJ+Dw5NhIkAili1Jc8aQVdveC0 iiHcT0k1WmzDK7I2F6Vvju/x4eePLjkeNzBRztqguT6tmtdJZHM/0jh/qtcmutCCOkGq YuIUEvnkL5r9+vnq1wNNV17PS4ULlxavODTN4DvF9cStAa1PMNt5S4sK2P5fBoXBV0FZ Wc0+K9BPOtf3pT3fHaWsL2LxEJyIV7XCrh6X2t+Py1o1obY/HEaLZQrS+MXF2Eugaa3Z SWHA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1788887859; x=1789492659; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=J/jv1ovVCNeCubLupVeuht7eNIRLVbkvYJqOaymhU6s=; b=DVOtB22+biodxMVRsK81dJlz5u8CTefdzyg7qKFVofrJzsaJlWpNhKOZTG4I5WhlTi +UWB8qxgkuttZhZ+P/MOj6seFgaktXqC73pb9lLy2yDJ3fExvhoxFPPyAYqpBoy1P0uc 2cAipFLtpXHB/foJ2SMD3ZIU9s43OcbXDXnZP7tQe74zPfDiss+7hwk79sdtypYqEohp iftB2L1yyqvBZwELPm4tha/LUPsJl0djL6o6aghPYAN2FD7FeX9gifr0QieKen95KbYq eu0Ruy3SiDPWcGCkRlDTJUXfchqUYcz84Zi0BDSRO2EXlt5desj1U5Z2gJtC+C9M9/nU uyGw== X-Forwarded-Encrypted: i=1; AKwUvBxSzXB0jPazmhyNKJ4nyTfgk+p6ZPVFr2JwvWBbEayDzs7HIgI8gUqPR6o4dU1GK5FA8gt7E9OfI9jkOA==@lists.linux.dev X-Gm-Message-State: AFuF++n0aEMSzNeCsqscEQlTNh/GsRJjd1VN1lroOSONM9GwwNyWJnUd xNfHHlOuVpCXhBYWOBa0SZG9MzVXtg54b2a7q/Gl+RemTGbkFJzmnzIPRYYDEc8O64r4omnZ2cM ceQ== X-Received: from pfbce7.prod.google.com ([2002:a05:6a00:2a07:b0:866:a8ba:a59]) (user=praan job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:1950:b0:85c:3922:25d5 with SMTP id d2e1a72fcca58-8616aa68194mr43353950b3a.21.1788887858247; Tue, 08 Sep 2026 10:17:38 -0700 (PDT) Date: Tue, 8 Sep 2026 17:17:06 +0000 In-Reply-To: <20260908171712.356645-1-praan@google.com> Precedence: bulk X-Mailing-List: driver-core@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260908171712.356645-1-praan@google.com> X-Mailer: git-send-email 2.55.0.979.g7e5102b832-goog Message-ID: <20260908171712.356645-11-praan@google.com> Subject: [PATCH v10 10/15] iommu/arm-smmu-v3: Add CMDQ_PROD_STOP_FLAG to gate CMDQ submissions From: Pranjal Shrivastava To: iommu@lists.linux.dev Cc: Will Deacon , Joerg Roedel , Robin Murphy , Jason Gunthorpe , Mostafa Saleh , Nicolin Chen , Daniel Mentz , Ashish Mhetre , linux-arm-kernel@lists.infradead.org, Greg Kroah-Hartman , rafael@kernel.org, Danilo Krummrich , Thomas Gleixner , driver-core@lists.linux.dev, Pranjal Shrivastava Content-Type: text/plain; charset="UTF-8" Introduce a new bit flag, CMDQ_PROD_STOP_FLAG (bit 30), in the command queue's producer index to safely gate command submissions during device suspension. The flag embeds the suspend state directly into the existing global state The flag is checked in the cmpxchg loop in arm_smmu_cmdq_issue_cmdlist(), which acts as a Point of Commitment, ensuring that no indices are reserved or committed once the SMMU begins suspending. This prevents a situation of "abandoned batches" where indices are incremented but commands are never written, which would otherwise lead to timeout during the drain poll. Update queue_inc_prod_n() to preserve this flag during index calculations, ensuring that any in-flight commands that successfully passed the point of commitment can proceed to completion while the flag remains set. Suggested-by: Daniel Mentz Reviewed-by: Nicolin Chen Signed-off-by: Pranjal Shrivastava --- drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 35 +++++++++++++++++++-- drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 5 +++ 2 files changed, 38 insertions(+), 2 deletions(-) diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c index 98af7c1fac94..65939a9b0619 100644 --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c @@ -218,7 +218,8 @@ static int queue_sync_prod_in(struct arm_smmu_queue *q) static u32 queue_inc_prod_n(struct arm_smmu_ll_queue *q, int n) { u32 prod = Q_POS(q, q->prod) + n; - return Q_OVF(q->prod) | Q_POS(q, prod); + + return Q_OVF(q->prod) | Q_STOP(q->prod) | Q_POS(q, prod); } static void queue_poll_init(struct arm_smmu_device *smmu, @@ -726,13 +727,42 @@ int __arm_smmu_cmdq_issue_cmdlist(struct arm_smmu_device *smmu, do { u64 old; + /* + * If the SMMU is suspended/suspending, any new CMDs are elided. + * This loop is the Point of Commitment. If we haven't cmpxchg'd + * our new indices yet, we can safely bail. Once the indices are + * committed, we MUST write valid commands to those slots to + * avoid indefinite polling in the drain function. + */ + if (Q_STOP(llq.prod)) { + local_irq_restore(flags); + return 0; + } + while (!queue_has_space(&llq, n + sync)) { local_irq_restore(flags); + + /* Avoid waiting for space if the SMMU is suspending */ + if (Q_STOP(READ_ONCE(cmdq->q.llq.prod))) + return 0; + if (arm_smmu_cmdq_poll_until_not_full(smmu, cmdq, &llq)) dev_err_ratelimited(smmu->dev, "CMDQ timeout\n"); local_irq_save(flags); } + /* + * If we exited the polling loop because the queue finally + * has space, but the STOP_FLAG was set during the poll, + * we must abort immediately. If we proceed, we will + * commit new commands beyond the Point of Commitment while + * the SMMU is suspending. + */ + if (Q_STOP(llq.prod)) { + local_irq_restore(flags); + return 0; + } + head.cons = llq.cons; head.prod = queue_inc_prod_n(&llq, n + sync) | CMDQ_PROD_OWNED_FLAG; @@ -779,7 +809,8 @@ int __arm_smmu_cmdq_issue_cmdlist(struct arm_smmu_device *smmu, /* b. Stop gathering work by clearing the owned flag */ prod = atomic_fetch_andnot_relaxed(CMDQ_PROD_OWNED_FLAG, &cmdq->q.llq.atomic.prod); - prod &= ~CMDQ_PROD_OWNED_FLAG; + /* Strip all metadata flags */ + prod &= CMDQ_PROD_IDX_MASK; /* * c. Wait for any gathered work to be written to the queue. diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h index deefb17e31eb..794b258550dd 100644 --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h @@ -394,6 +394,11 @@ static inline unsigned int arm_smmu_cdtab_l2_idx(unsigned int ssid) #define CMDQ_ERR_CERROR_ATC_INV_IDX 3 #define CMDQ_PROD_OWNED_FLAG Q_OVERFLOW_FLAG +#define CMDQ_PROD_STOP_FLAG (1U << 30) +#define Q_STOP(p) ((p) & CMDQ_PROD_STOP_FLAG) + +/* Mask out software-only metadata flags to get the pure queue index/wrap bits */ +#define CMDQ_PROD_IDX_MASK ~(CMDQ_PROD_STOP_FLAG | CMDQ_PROD_OWNED_FLAG) struct arm_smmu_cmd { u64 data[CMDQ_ENT_DWORDS]; -- 2.55.0.979.g7e5102b832-goog