netdev - [PATCH net] pds_core: Fix pdsc_check_pci_health function to print warning

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Message-ID: <20240321063954.18711-1-brett.creeley@amd.com>
Date: Wed, 20 Mar 2024 23:39:54 -0700
From: Brett Creeley <brett.creeley@....com>
To: <davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
	<pabeni@...hat.com>, <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC: <shannon.nelson@....com>, <brett.creeley@....com>
Subject: [PATCH net] pds_core: Fix pdsc_check_pci_health function to print warning

When the driver notices fw_status == 0xff it tries to perform a PCI
reset on itself via pci_reset_function() in the context of the driver's
health thread. However, pdsc_reset_prepare calls
pdsc_stop_health_thread(), which attempts to stop/flush the health
thread. This results in a deadlock because the stop/flush will never
complete since the driver called pci_reset_function() from the health
thread context. Fix this by changing the pdsc_check_pci_health_function()
to print a dev_warn() once every fw_down/fw_up cycle and requiring the
user to perform a reset on the device via sysfs's reset interface,
reloading the driver, rebinding the device, etc.

Unloading the driver in the fw_down/dead state uncovered another issue,
which can be seen in the following trace:

WARNING: CPU: 51 PID: 6914 at kernel/workqueue.c:1450 __queue_work+0x358/0x440
[...]
RIP: 0010:__queue_work+0x358/0x440
[...]
Call Trace:
 <TASK>
 ? __warn+0x85/0x140
 ? __queue_work+0x358/0x440
 ? report_bug+0xfc/0x1e0
 ? handle_bug+0x3f/0x70
 ? exc_invalid_op+0x17/0x70
 ? asm_exc_invalid_op+0x1a/0x20
 ? __queue_work+0x358/0x440
 queue_work_on+0x28/0x30
 pdsc_devcmd_locked+0x96/0xe0 [pds_core]
 pdsc_devcmd_reset+0x71/0xb0 [pds_core]
 pdsc_teardown+0x51/0xe0 [pds_core]
 pdsc_remove+0x106/0x200 [pds_core]
 pci_device_remove+0x37/0xc0
 device_release_driver_internal+0xae/0x140
 driver_detach+0x48/0x90
 bus_remove_driver+0x6d/0xf0
 pci_unregister_driver+0x2e/0xa0
 pdsc_cleanup_module+0x10/0x780 [pds_core]
 __x64_sys_delete_module+0x142/0x2b0
 ? syscall_trace_enter.isra.18+0x126/0x1a0
 do_syscall_64+0x3b/0x90
 entry_SYSCALL_64_after_hwframe+0x72/0xdc
RIP: 0033:0x7fbd9d03a14b
[...]

Fix this by preventing the devcmd reset if the FW is not running.

Fixes: d9407ff11809 ("pds_core: Prevent health thread from running during reset/remove")
Reviewed-by: Shannon Nelson <shannon.nelson@....com>
Signed-off-by: Brett Creeley <brett.creeley@....com>
---
 drivers/net/ethernet/amd/pds_core/core.c | 9 ++++++++-
 drivers/net/ethernet/amd/pds_core/core.h | 1 +
 drivers/net/ethernet/amd/pds_core/dev.c  | 3 +++
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/amd/pds_core/core.c b/drivers/net/ethernet/amd/pds_core/core.c
index 9662ee72814c..8e5e3797cf0c 100644
--- a/drivers/net/ethernet/amd/pds_core/core.c
+++ b/drivers/net/ethernet/amd/pds_core/core.c
@@ -587,6 +587,9 @@ void pdsc_fw_up(struct pdsc *pdsc)
 						     DEVLINK_HEALTH_REPORTER_STATE_HEALTHY);
 	pdsc_notify(PDS_EVENT_RESET, &reset_event);
 
+	/* Allow for fw_status == 0xff to print another warning */
+	pdsc->bad_pci_warned = false;
+
 	return;
 
 err_out:
@@ -607,7 +610,11 @@ static void pdsc_check_pci_health(struct pdsc *pdsc)
 	if (fw_status != PDS_RC_BAD_PCI)
 		return;
 
-	pci_reset_function(pdsc->pdev);
+	if (!pdsc->bad_pci_warned) {
+		dev_warn(pdsc->dev, "fw not reachable due to failed PCI connection, fw_status = 0x%x\n",
+			 fw_status);
+		pdsc->bad_pci_warned = true;
+	}
 }
 
 void pdsc_health_thread(struct work_struct *work)
diff --git a/drivers/net/ethernet/amd/pds_core/core.h b/drivers/net/ethernet/amd/pds_core/core.h
index 92d7657dd614..10979118be00 100644
--- a/drivers/net/ethernet/amd/pds_core/core.h
+++ b/drivers/net/ethernet/amd/pds_core/core.h
@@ -165,6 +165,7 @@ struct pdsc {
 	unsigned long state;
 	u8 fw_status;
 	u8 fw_generation;
+	bool bad_pci_warned;
 	unsigned long last_fw_time;
 	u32 last_hb;
 	struct timer_list wdtimer;
diff --git a/drivers/net/ethernet/amd/pds_core/dev.c b/drivers/net/ethernet/amd/pds_core/dev.c
index e494e1298dc9..495ef4ef8c10 100644
--- a/drivers/net/ethernet/amd/pds_core/dev.c
+++ b/drivers/net/ethernet/amd/pds_core/dev.c
@@ -229,6 +229,9 @@ int pdsc_devcmd_reset(struct pdsc *pdsc)
 		.reset.opcode = PDS_CORE_CMD_RESET,
 	};
 
+	if (!pdsc_is_fw_running(pdsc))
+		return 0;
+
 	return pdsc_devcmd(pdsc, &cmd, &comp, pdsc->devcmd_timeout);
 }
 
-- 
2.17.1