From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pg1-f198.google.com (mail-pg1-f198.google.com [209.85.215.198]) (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 C134F430309 for ; Tue, 29 Sep 2026 03:45:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.198 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790653550; cv=none; b=bXicGG9h/EcmQZrrwBxmgoeo+Sb/7RiobXevqiX5moCprGjg2TY1E1dbtIpBkp+OQpc1F57fpOL1n7Xo2zONsZ+NNNU9c/NUgffghGRGMCyr/sp1zKb+HrbLBF33ykVs0QExYYnZ6qvpv0wVFUzK3y1YXxK+Dsoad+wUET3fmQY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790653550; c=relaxed/simple; bh=emN7DAxtSRLF415z6jBFS1BVT82Ombe4VPgOdgIfbVQ=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=D45V8BZidmUM0446Y/wBQnqbvEFJKNOgGwFZN7VVvGjfg1kvfhQXhvuGmcDAm3WMIs+5CggZVXpr0gRytI2oDAT7qExigJcYOB9L50/WRVE3Ox8CSrtEGqWcY0NqXwtYFpAxvs/9vL+ZGdk2AlOCM+uj4tVLiDpXWhN88p5P/4E= 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=GOCwsQxq; arc=none smtp.client-ip=209.85.215.198 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="GOCwsQxq" Received: by mail-pg1-f198.google.com with SMTP id 41be03b00d2f7-cc51591102fso2532126a12.1 for ; Mon, 28 Sep 2026 20:45:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1790653547; x=1791258347; darn=vger.kernel.org; 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=DJUc8W66LdXd5niQlho6vVTddWB/e8RRGn6UCJy7ACg=; b=GOCwsQxqdyIXirXzgGoj+9nuGcbeM9taIC6m5ob5HMGb2y2JzwP9cXG2zgUkKhwzLU eiCIxAh2AfftNZMmLvnFDiuDeq6J5jjUTQB7vDhjWW864Aif8u9lz0vqKJGkmhNpr1VA tClcnt/6kUQPpaCcBewiH9s6Qx5GwsTl/qHpmXmeTES6V/4W/dIfoIFmVTzmObROtPUe /54IyXjDefYxufYT2maPgcf4XaWuUdITm0HjmSzwJrSJ4lN6D2KYPJBLKSWknN0ilMen bPcvea/UzuSvDqQ6yVuJQksePP7iAoDcUTfgtujK/zA0igVZjSwFGkO7nthr9gWaaI8c TdKw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1790653547; x=1791258347; 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=DJUc8W66LdXd5niQlho6vVTddWB/e8RRGn6UCJy7ACg=; b=OM5mnlO4Oo9x6I7AT0yIpw3RK1sJohIydQxgC67MTROkGnLp96Rn5OizShqF3GmKmF tkvfu6rK51g5fDL9P2HMWrdo+GX8vKyZIfotawqTcxxM2dTLLzcaA+zPYWpgAyukI5mi MpOkFGS+wkhaEZzmhVvtaKTckTaocpYbrWI0dqto3RE/6imrxnns+6cv70IlTcDJNEP7 eoThHGZ5ws4m7iBN59/35qCIepcr0XcjIGbKKJkyv/s8HOM/r0oWOCZ9H6Vy3LzAYsJY PpuB2avRrJCzbbdCaqO6ItpRvgkyvgYlz7XIfWfm3oxAZBwL0iFmjDaSGdSyawjxPevw KyMg== X-Forwarded-Encrypted: i=1; AKwUvBxpRUU7xD3CfMCZL4boTjZ3GW3z3Jtn35+/pd/NsAiT3+FPSLOOrPf4oIb2Ry272ALpb+8mWLBxB8BgtII=@vger.kernel.org X-Gm-Message-State: AFuF++n0SJQo6B7MYlOKrZpEvDYUGzI3i88pEwDvHIUKlIj3cWU8v6MZ vs3YLmCHd5BHJPICyqaYI4eRhX7kO6j8/oMnINK96WxreUBiZwpBPQSMc+oUnwvU/m3CV6J+ya1 zbw== X-Received: from pgdf1.prod.google.com ([2002:a05:6a02:5141:b0:cc7:56f1:71ad]) (user=praan job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a21:6f06:b0:3d3:ae40:51e5 with SMTP id adf61e73a8af0-3de0e750b0dmr13391618637.25.1790653546468; Mon, 28 Sep 2026 20:45:46 -0700 (PDT) Date: Tue, 29 Sep 2026 03:45:05 +0000 In-Reply-To: <20260929034510.2023173-1-praan@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260929034510.2023173-1-praan@google.com> X-Mailer: git-send-email 2.56.0.rc1.315.gc6ed9934b7-goog Message-ID: <20260929034510.2023173-12-praan@google.com> Subject: [PATCH v11 11/16] 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, Thomas Gleixner , Radu Rendec , Bjorn Helgaas , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, Greg Kroah-Hartman , rafael@kernel.org, Danilo Krummrich , 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 a123810fac57..7f89e2306942 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]; -- 2.56.0.rc1.315.gc6ed9934b7-goog