From: Sergei Miroshnichenko <s.miroshnichenko@yadro.com>
To: <linux-pci@vger.kernel.org>
Cc: "Bjorn Helgaas" <helgaas@kernel.org>,
"Lukas Wunner" <lukas@wunner.de>, "Stefan Roese" <sr@denx.de>,
"Andy Lavr" <andy.lavr@gmail.com>,
"Christian König" <christian.koenig@amd.com>,
"Ard Biesheuvel" <ardb@kernel.org>,
"David Laight" <David.Laight@ACULAB.COM>,
"Rajat Jain" <rajatja@google.com>,
linux@yadro.com,
"Sergei Miroshnichenko" <s.miroshnichenko@yadro.com>,
"Srinath Mannam" <srinath.mannam@broadcom.com>,
"Marta Rybczynska" <mrybczyn@kalray.eu>
Subject: [PATCH v8 01/24] PCI: Fix race condition in pci_enable/disable_device()
Date: Mon, 27 Apr 2020 21:23:35 +0300 [thread overview]
Message-ID: <20200427182358.2067702-2-s.miroshnichenko@yadro.com> (raw)
In-Reply-To: <20200427182358.2067702-1-s.miroshnichenko@yadro.com>
This is a yet another approach to fix an old [1-2] concurrency issue, when:
- two or more devices are being hot-added into a bridge which was
initially empty;
- a bridge with two or more devices is being hot-added;
- during boot, if BIOS/bootloader/firmware doesn't pre-enable bridges.
The problem is that a bridge is reported as enabled before the MEM/IO bits
are actually written to the PCI_COMMAND register, so another driver thread
starts memory requests through the not-yet-enabled bridge:
CPU0 CPU1
pci_enable_device_mem() pci_enable_device_mem()
pci_enable_bridge() pci_enable_bridge()
pci_is_enabled()
return false;
atomic_inc_return(enable_cnt)
Start actual enabling the bridge
... pci_is_enabled()
... return true;
... Start memory requests <-- FAIL
...
Set the PCI_COMMAND_MEMORY bit <-- Must wait for this
Protect the pci_enable/disable_device() and pci_enable_bridge(), which is
similar to the previous solution from commit 40f11adc7cd9 ("PCI: Avoid race
while enabling upstream bridges"), but adding a per-device mutexes and
preventing the dev->enable_cnt from from incrementing early.
CC: Srinath Mannam <srinath.mannam@broadcom.com>
CC: Marta Rybczynska <mrybczyn@kalray.eu>
Signed-off-by: Sergei Miroshnichenko <s.miroshnichenko@yadro.com>
[1] https://lore.kernel.org/linux-pci/1501858648-22228-1-git-send-email-srinath.mannam@broadcom.com/T/#u
[RFC PATCH v3] pci: Concurrency issue during pci enable bridge
[2] https://lore.kernel.org/linux-pci/744877924.5841545.1521630049567.JavaMail.zimbra@kalray.eu/T/#u
[RFC PATCH] nvme: avoid race-conditions when enabling devices
---
drivers/pci/pci.c | 27 +++++++++++++++++++++++----
drivers/pci/probe.c | 1 +
include/linux/pci.h | 1 +
3 files changed, 25 insertions(+), 4 deletions(-)
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 595fcf59843f..d7819be809a3 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1733,6 +1733,8 @@ static void pci_enable_bridge(struct pci_dev *dev)
struct pci_dev *bridge;
int retval;
+ mutex_lock(&dev->enable_mutex);
+
bridge = pci_upstream_bridge(dev);
if (bridge)
pci_enable_bridge(bridge);
@@ -1740,6 +1742,7 @@ static void pci_enable_bridge(struct pci_dev *dev)
if (pci_is_enabled(dev)) {
if (!dev->is_busmaster)
pci_set_master(dev);
+ mutex_unlock(&dev->enable_mutex);
return;
}
@@ -1748,11 +1751,14 @@ static void pci_enable_bridge(struct pci_dev *dev)
pci_err(dev, "Error enabling bridge (%d), continuing\n",
retval);
pci_set_master(dev);
+ mutex_unlock(&dev->enable_mutex);
}
static int pci_enable_device_flags(struct pci_dev *dev, unsigned long flags)
{
struct pci_dev *bridge;
+ /* Enable-locking of bridges is performed within the pci_enable_bridge() */
+ bool need_lock = !dev->subordinate;
int err;
int i, bars = 0;
@@ -1768,8 +1774,13 @@ static int pci_enable_device_flags(struct pci_dev *dev, unsigned long flags)
dev->current_state = (pmcsr & PCI_PM_CTRL_STATE_MASK);
}
- if (atomic_inc_return(&dev->enable_cnt) > 1)
+ if (need_lock)
+ mutex_lock(&dev->enable_mutex);
+ if (pci_is_enabled(dev)) {
+ if (need_lock)
+ mutex_unlock(&dev->enable_mutex);
return 0; /* already enabled */
+ }
bridge = pci_upstream_bridge(dev);
if (bridge)
@@ -1784,8 +1795,10 @@ static int pci_enable_device_flags(struct pci_dev *dev, unsigned long flags)
bars |= (1 << i);
err = do_pci_enable_device(dev, bars);
- if (err < 0)
- atomic_dec(&dev->enable_cnt);
+ if (err >= 0)
+ atomic_inc(&dev->enable_cnt);
+ if (need_lock)
+ mutex_unlock(&dev->enable_mutex);
return err;
}
@@ -2029,15 +2042,21 @@ void pci_disable_device(struct pci_dev *dev)
if (dr)
dr->enabled = 0;
+ mutex_lock(&dev->enable_mutex);
+
dev_WARN_ONCE(&dev->dev, atomic_read(&dev->enable_cnt) <= 0,
"disabling already-disabled device");
- if (atomic_dec_return(&dev->enable_cnt) != 0)
+ if (atomic_dec_return(&dev->enable_cnt) != 0) {
+ mutex_unlock(&dev->enable_mutex);
return;
+ }
do_pci_disable_device(dev);
dev->is_busmaster = 0;
+
+ mutex_unlock(&dev->enable_mutex);
}
EXPORT_SYMBOL(pci_disable_device);
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 77b8a145c39b..dd169e2935df 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2210,6 +2210,7 @@ struct pci_dev *pci_alloc_dev(struct pci_bus *bus)
INIT_LIST_HEAD(&dev->bus_list);
dev->dev.type = &pci_dev_type;
dev->bus = pci_bus_get(bus);
+ mutex_init(&dev->enable_mutex);
return dev;
}
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 83ce1cdf5676..d3c9fc20fc1f 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -431,6 +431,7 @@ struct pci_dev {
unsigned int no_vf_scan:1; /* Don't scan for VFs after IOV enablement */
pci_dev_flags_t dev_flags;
atomic_t enable_cnt; /* pci_enable_device has been called */
+ struct mutex enable_mutex;
u32 saved_config_space[16]; /* Config space saved at suspend time */
struct hlist_head saved_cap_space;
--
2.24.1
next prev parent reply other threads:[~2020-04-27 18:24 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-27 18:23 [PATCH v8 00/24] PCI: Allow BAR movement during boot and hotplug Sergei Miroshnichenko
2020-04-27 18:23 ` Sergei Miroshnichenko [this message]
2020-04-27 18:23 ` [PATCH v8 02/24] PCI: Ensure a bridge has I/O and MEM access for hot-added devices Sergei Miroshnichenko
2020-04-29 6:30 ` kbuild test robot
2020-04-27 18:23 ` [PATCH v8 03/24] PCI: hotplug: Initial support of the movable BARs feature Sergei Miroshnichenko
2020-04-27 18:23 ` [PATCH v8 04/24] PCI: Add version of release_child_resources() aware of fixed BARs Sergei Miroshnichenko
2020-04-27 18:23 ` [PATCH v8 05/24] PCI: hotplug: Fix reassigning the released BARs Sergei Miroshnichenko
2020-04-27 18:23 ` [PATCH v8 06/24] PCI: hotplug: Recalculate every bridge window during rescan Sergei Miroshnichenko
2020-04-27 18:23 ` [PATCH v8 07/24] PCI: hotplug: Don't allow hot-added devices to steal resources Sergei Miroshnichenko
2020-04-27 18:23 ` [PATCH v8 08/24] PCI: Reassign BARs if BIOS/bootloader had assigned not all of them Sergei Miroshnichenko
2020-04-27 18:23 ` [PATCH v8 09/24] PCI: hotplug: Try to reassign movable BARs only once Sergei Miroshnichenko
2020-04-27 18:23 ` [PATCH v8 10/24] PCI: hotplug: Calculate fixed parts of bridge windows Sergei Miroshnichenko
2020-04-27 18:23 ` [PATCH v8 11/24] PCI: Include fixed BARs into the bus size calculating Sergei Miroshnichenko
2020-04-27 18:23 ` [PATCH v8 12/24] PCI: hotplug: movable BARs: Compute limits for relocated bridge windows Sergei Miroshnichenko
2020-04-27 18:23 ` [PATCH v8 13/24] PCI: Make sure bridge windows include their fixed BARs Sergei Miroshnichenko
2020-04-27 18:23 ` [PATCH v8 14/24] PCI: hotplug: Add support of fixed BARs to pci_assign_resource() Sergei Miroshnichenko
2020-04-27 18:23 ` [PATCH v8 15/24] PCI: hotplug: Sort fixed BARs before assignment Sergei Miroshnichenko
2020-04-27 18:23 ` [PATCH v8 16/24] x86/PCI/ACPI: Fix up PCIBIOS_MIN_MEM if value computed from e820 is invalid Sergei Miroshnichenko
2020-04-27 18:23 ` [PATCH v8 17/24] PCI: hotplug: Configure MPS after manual bus rescan Sergei Miroshnichenko
2020-04-27 18:23 ` [PATCH v8 18/24] PCI: hotplug: Don't disable the released bridge windows immediately Sergei Miroshnichenko
2020-04-27 18:23 ` [PATCH v8 19/24] PCI: pciehp: Trigger a domain rescan on hp events when enabled movable BARs Sergei Miroshnichenko
2020-04-27 18:23 ` [PATCH v8 20/24] PCI: Don't claim fixed BARs Sergei Miroshnichenko
2020-04-27 18:23 ` [PATCH v8 21/24] PCI: hotplug: Don't reserve bus space when enabled movable BARs Sergei Miroshnichenko
2020-04-27 18:23 ` [PATCH v8 22/24] PCI: hotplug: Enable the movable BARs feature by default Sergei Miroshnichenko
2020-04-27 18:23 ` [PATCH v8 23/24] PCI/portdrv: Declare support of movable BARs Sergei Miroshnichenko
2020-04-27 18:23 ` [PATCH v8 24/24] nvme-pci: Handle " Sergei Miroshnichenko
2020-04-28 12:59 ` [PATCH v8 00/24] PCI: Allow BAR movement during boot and hotplug Christian König
2020-05-04 9:30 ` Sergei Miroshnichenko
2020-08-10 22:21 ` Bjorn Helgaas
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