[PATCH 2/3] PCI: Introduce per-device reset_ready_poll override

From: Stanislav Spassov <stanspas@amazon.com>
To: <linux-pci@vger.kernel.org>
Cc: "Stanislav Spassov" <stanspas@amazon.de>,
	"Bjorn Helgaas" <bhelgaas@google.com>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Jan H . Schönherr" <jschoenh@amazon.de>,
	"Wei Wang" <wawei@amazon.de>
Subject: [PATCH 2/3] PCI: Introduce per-device reset_ready_poll override
Date: Sun, 23 Feb 2020 13:20:56 +0100	[thread overview]
Message-ID: <20200223122057.6504-3-stanspas@amazon.com> (raw)
In-Reply-To: <20200223122057.6504-1-stanspas@amazon.com>

From: Stanislav Spassov <stanspas@amazon.de>

A broken device may never become responsive after reset, hence the need
for a timeout. However, waiting for too long can have unintended side
effects such as triggering hung task timeouts for processes waiting on
a lock held during the reset. Locks that are shared across multiple
devices, such as VFIO's per-bus reflck, are especially problematic,
because a single broken VF can cause hangs for processes working with
other VFs on the same bus.

To allow lowering the global default post-reset timeout, while still
accommodating devices that require more time, this patch introduces
a per-device override that can be configured via a quirk.

Signed-off-by: Stanislav Spassov <stanspas@amazon.de>
---
 drivers/pci/pci.c   | 19 ++++++++++++++-----
 drivers/pci/probe.c |  2 ++
 include/linux/pci.h |  1 +
 3 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index db9b58ab6c68..a554818968ed 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1033,8 +1033,17 @@ void pci_wakeup_bus(struct pci_bus *bus)
 		pci_walk_bus(bus, pci_wakeup, NULL);
 }
 
-static int pci_dev_wait(struct pci_dev *dev, char *reset_type, int timeout)
+static int pci_dev_get_reset_ready_poll_ms(struct pci_dev *dev)
 {
+	if (dev->reset_ready_poll_ms >= 0)
+		return dev->reset_ready_poll_ms;
+
+	return pcie_reset_ready_poll_ms;
+}
+
+static int pci_dev_wait(struct pci_dev *dev, char *reset_type)
+{
+	int timeout = pci_dev_get_reset_ready_poll_ms(dev);
 	int delay = 1;
 	u32 id;
 
@@ -4518,7 +4527,7 @@ int pcie_flr(struct pci_dev *dev)
 	 */
 	msleep(100);
 
-	return pci_dev_wait(dev, "FLR", pcie_reset_ready_poll_ms);
+	return pci_dev_wait(dev, "FLR");
 }
 EXPORT_SYMBOL_GPL(pcie_flr);
 
@@ -4563,7 +4572,7 @@ static int pci_af_flr(struct pci_dev *dev, int probe)
 	 */
 	msleep(100);
 
-	return pci_dev_wait(dev, "AF_FLR", pcie_reset_ready_poll_ms);
+	return pci_dev_wait(dev, "AF_FLR");
 }
 
 /**
@@ -4608,7 +4617,7 @@ static int pci_pm_reset(struct pci_dev *dev, int probe)
 	pci_write_config_word(dev, dev->pm_cap + PCI_PM_CTRL, csr);
 	pci_dev_d3_sleep(dev);
 
-	return pci_dev_wait(dev, "PM D3hot->D0", pcie_reset_ready_poll_ms);
+	return pci_dev_wait(dev, "PM D3hot->D0");
 }
 
 /**
@@ -4838,7 +4847,7 @@ int pci_bridge_secondary_bus_reset(struct pci_dev *dev)
 {
 	pcibios_reset_secondary_bus(dev);
 
-	return pci_dev_wait(dev, "bus reset", pcie_reset_ready_poll_ms);
+	return pci_dev_wait(dev, "bus reset");
 }
 EXPORT_SYMBOL_GPL(pci_bridge_secondary_bus_reset);
 
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 512cb4312ddd..eeb79a45d504 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2166,6 +2166,8 @@ struct pci_dev *pci_alloc_dev(struct pci_bus *bus)
 	if (!dev)
 		return NULL;
 
+	dev->reset_ready_poll_ms = -1;
+
 	INIT_LIST_HEAD(&dev->bus_list);
 	dev->dev.type = &pci_dev_type;
 	dev->bus = pci_bus_get(bus);
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 3840a541a9de..049a41b9412b 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -468,6 +468,7 @@ struct pci_dev {
 	size_t		romlen;		/* Length if not from BAR */
 	char		*driver_override; /* Driver name to force a match */
 
+	int		reset_ready_poll_ms;
 	unsigned long	priv_flags;	/* Private flags for the PCI driver */
 };
 
-- 
2.25.1




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