linux-kernel - [PATCH 6.6.y 1/1] pds_core: Prevent possible adminq overflow/stuck condition

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Message-ID: <20250523175835.3522650-2-alperyasinak1@gmail.com>
Date: Fri, 23 May 2025 20:58:35 +0300
From: Alper Ak <alperyasinak1@...il.com>
To: shannon.nelson@....com,
	brett.creeley@....com,
	davem@...emloft.net,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: stable@...r.kernel.org,
	alperyasinak1@...il.com,
	Michal Swiatkowski <michal.swiatkowski@...ux.intel.com>,
	Simon Horman <horms@...nel.org>,
	Jacob Keller <jacob.e.keller@...el.com>,
	Sasha Levin <sashal@...nel.org>
Subject: [PATCH 6.6.y 1/1] pds_core: Prevent possible adminq overflow/stuck condition

From: Brett Creeley <brett.creeley@....com>

[ Upstream commit d9e2f070d8af60f2c8c02b2ddf0a9e90b4e9220c ]

The pds_core's adminq is protected by the adminq_lock, which prevents
more than 1 command to be posted onto it at any one time. This makes it
so the client drivers cannot simultaneously post adminq commands.
However, the completions happen in a different context, which means
multiple adminq commands can be posted sequentially and all waiting
on completion.

On the FW side, the backing adminq request queue is only 16 entries
long and the retry mechanism and/or overflow/stuck prevention is
lacking. This can cause the adminq to get stuck, so commands are no
longer processed and completions are no longer sent by the FW.

As an initial fix, prevent more than 16 outstanding adminq commands so
there's no way to cause the adminq from getting stuck. This works
because the backing adminq request queue will never have more than 16
pending adminq commands, so it will never overflow. This is done by
reducing the adminq depth to 16.

Fixes: 45d76f492938 ("pds_core: set up device and adminq")
Reviewed-by: Michal Swiatkowski <michal.swiatkowski@...ux.intel.com>
Reviewed-by: Simon Horman <horms@...nel.org>
Signed-off-by: Brett Creeley <brett.creeley@....com>
Signed-off-by: Shannon Nelson <shannon.nelson@....com>
Reviewed-by: Jacob Keller <jacob.e.keller@...el.com>
Link: https://patch.msgid.link/20250421174606.3892-2-shannon.nelson@amd.com
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
(cherry picked from commit 2982e07ad72b48eb12c29a87a3f2126ea552688c)
Signed-off-by: Alper Ak <alperyasinak1@...il.com>
---
 drivers/net/ethernet/amd/pds_core/core.c | 5 +----
 drivers/net/ethernet/amd/pds_core/core.h | 2 +-
 2 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/amd/pds_core/core.c b/drivers/net/ethernet/amd/pds_core/core.c
index b3fa867c8ccd..c2ef55cff6b3 100644
--- a/drivers/net/ethernet/amd/pds_core/core.c
+++ b/drivers/net/ethernet/amd/pds_core/core.c
@@ -413,10 +413,7 @@ int pdsc_setup(struct pdsc *pdsc, bool init)
 	if (err)
 		return err;

-	/* Scale the descriptor ring length based on number of CPUs and VFs */
-	numdescs = max_t(int, PDSC_ADMINQ_MIN_LENGTH, num_online_cpus());
-	numdescs += 2 * pci_sriov_get_totalvfs(pdsc->pdev);
-	numdescs = roundup_pow_of_two(numdescs);
+	numdescs = PDSC_ADMINQ_MAX_LENGTH;
 	err = pdsc_qcq_alloc(pdsc, PDS_CORE_QTYPE_ADMINQ, 0, "adminq",
 			     PDS_CORE_QCQ_F_CORE | PDS_CORE_QCQ_F_INTR,
 			     numdescs,
diff --git a/drivers/net/ethernet/amd/pds_core/core.h b/drivers/net/ethernet/amd/pds_core/core.h
index 61ee607ee48a..421371408503 100644
--- a/drivers/net/ethernet/amd/pds_core/core.h
+++ b/drivers/net/ethernet/amd/pds_core/core.h
@@ -16,7 +16,7 @@

 #define PDSC_WATCHDOG_SECS	5
 #define PDSC_QUEUE_NAME_MAX_SZ  16
-#define PDSC_ADMINQ_MIN_LENGTH	16	/* must be a power of two */
+#define PDSC_ADMINQ_MAX_LENGTH	16	/* must be a power of two */
 #define PDSC_NOTIFYQ_LENGTH	64	/* must be a power of two */
 #define PDSC_TEARDOWN_RECOVERY	false
 #define PDSC_TEARDOWN_REMOVING	true
--
2.43.0