linux-kernel - [PATCH AUTOSEL 5.4 3/4] iommu/arm-smmu-v3: Acknowledge pri/event queue overflow if any

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-Id: <20230509212058.22651-3-sashal@kernel.org>
Date:   Tue,  9 May 2023 17:20:55 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Tomas Krcka <krckatom@...zon.de>, Will Deacon <will@...nel.org>,
        Sasha Levin <sashal@...nel.org>, joro@...tes.org,
        iommu@...ts.linux.dev
Subject: [PATCH AUTOSEL 5.4 3/4] iommu/arm-smmu-v3: Acknowledge pri/event queue overflow if any

From: Tomas Krcka <krckatom@...zon.de>

[ Upstream commit 67ea0b7ce41844eae7c10bb04dfe66a23318c224 ]

When an overflow occurs in the PRI queue, the SMMU toggles the overflow
flag in the PROD register. To exit the overflow condition, the PRI thread
is supposed to acknowledge it by toggling this flag in the CONS register.
Unacknowledged overflow causes the queue to stop adding anything new.

Currently, the priq thread always writes the CONS register back to the
SMMU after clearing the queue.

The writeback is not necessary if the OVFLG in the PROD register has not
been changed, no overflow has occured.

This commit checks the difference of the overflow flag between CONS and
PROD register. If it's different, toggles the OVACKFLG flag in the CONS
register and write it to the SMMU.

The situation is similar for the event queue.
The acknowledge register is also toggled after clearing the event
queue but never propagated to the hardware. This would only be done the
next time when executing evtq thread.

Unacknowledged event queue overflow doesn't affect the event
queue, because the SMMU still adds elements to that queue when the
overflow condition is active.
But it feel nicer to keep SMMU in sync when possible, so use the same
way here as well.

Signed-off-by: Tomas Krcka <krckatom@...zon.de>
Link: https://lore.kernel.org/r/20230329123420.34641-1-tomas.krcka@gmail.com
Signed-off-by: Will Deacon <will@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/iommu/arm-smmu-v3.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index 4f64c3a9ee88d..b3c5d7b4547a4 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c
@@ -760,6 +760,18 @@ static void queue_inc_cons(struct arm_smmu_ll_queue *q)
 	q->cons = Q_OVF(q->cons) | Q_WRP(q, cons) | Q_IDX(q, cons);
 }

+static void queue_sync_cons_ovf(struct arm_smmu_queue *q)
+{
+	struct arm_smmu_ll_queue *llq = &q->llq;
+
+	if (likely(Q_OVF(llq->prod) == Q_OVF(llq->cons)))
+		return;
+
+	llq->cons = Q_OVF(llq->prod) | Q_WRP(llq, llq->cons) |
+		      Q_IDX(llq, llq->cons);
+	queue_sync_cons_out(q);
+}
+
 static int queue_sync_prod_in(struct arm_smmu_queue *q)
 {
 	int ret = 0;
@@ -1720,8 +1732,7 @@ static irqreturn_t arm_smmu_evtq_thread(int irq, void *dev)
 	} while (!queue_empty(llq));

 	/* Sync our overflow flag, as we believe we're up to speed */
-	llq->cons = Q_OVF(llq->prod) | Q_WRP(llq, llq->cons) |
-		    Q_IDX(llq, llq->cons);
+	queue_sync_cons_ovf(q);
 	return IRQ_HANDLED;
 }

@@ -1779,9 +1790,7 @@ static irqreturn_t arm_smmu_priq_thread(int irq, void *dev)
 	} while (!queue_empty(llq));

 	/* Sync our overflow flag, as we believe we're up to speed */
-	llq->cons = Q_OVF(llq->prod) | Q_WRP(llq, llq->cons) |
-		      Q_IDX(llq, llq->cons);
-	queue_sync_cons_out(q);
+	queue_sync_cons_ovf(q);
 	return IRQ_HANDLED;
 }

-- 
2.39.2