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From: Dexuan Cui <decui@microsoft.com>
To: "lorenzo.pieralisi@arm.com" <lorenzo.pieralisi@arm.com>,
	"bhelgaas@google.com" <bhelgaas@google.com>,
	"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
	KY Srinivasan <kys@microsoft.com>,
	Stephen Hemminger <sthemmin@microsoft.com>,
	Michael Kelley <mikelley@microsoft.com>,
	Sasha Levin <Alexander.Levin@microsoft.com>
Cc: "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"driverdev-devel@linuxdriverproject.org" 
	<driverdev-devel@linuxdriverproject.org>,
	Haiyang Zhang <haiyangz@microsoft.com>,
	"olaf@aepfle.de" <olaf@aepfle.de>,
	"apw@canonical.com" <apw@canonical.com>,
	"jasowang@redhat.com" <jasowang@redhat.com>,
	vkuznets <vkuznets@redhat.com>,
	"marcelo.cerri@canonical.com" <marcelo.cerri@canonical.com>,
	"jackm@mellanox.com" <jackm@mellanox.com>,
	Dexuan Cui <decui@microsoft.com>,
	"stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: [PATCH 3/3] PCI: hv: Add pci_destroy_slot() in pci_devices_present_work(), if necessary
Date: Mon, 4 Mar 2019 21:34:49 +0000
Message-ID: <20190304213357.16652-4-decui@microsoft.com> (raw)
In-Reply-To: <20190304213357.16652-1-decui@microsoft.com>

When we hot-remove a device, usually the host sends us a PCI_EJECT message,
and a PCI_BUS_RELATIONS message with bus_rel->device_count == 0. But when
we do the quick hot-add/hot-remove test, the host may not send us the
PCI_EJECT message, if the guest has not fully finished the initialization
by sending the PCI_RESOURCES_ASSIGNED* message to the host, so it's
potentially unsafe to only depend on the pci_destroy_slot() in
hv_eject_device_work(), though create_root_hv_pci_bus() ->
hv_pci_assign_slots() is not called in this case. Note: in this case, the
host still sends the guest a PCI_BUS_RELATIONS message with
bus_rel->device_count == 0.

And, in the quick hot-add/hot-remove test, we can have such a race: before
pci_devices_present_work() -> new_pcichild_device() adds the new device
into hbus->children, we may have already received the PCI_EJECT message,
and hence the taklet handler hv_pci_onchannelcallback() may fail to find
the "hpdev" by get_pcichild_wslot(hbus, dev_message->wslot.slot), so
hv_pci_eject_device() is NOT called; later create_root_hv_pci_bus() ->
hv_pci_assign_slots() creates the slot, and the PCI_BUS_RELATIONS message
with bus_rel->device_count == 0 removes the device from hbus->children, and
we end up being unable to remove the slot in hv_pci_remove() ->
hv_pci_remove_slots().

The patch removes the slot in pci_devices_present_work() when the device
is removed. This can address the above race. Note 1:
pci_devices_present_work() and hv_eject_device_work() run in the
singled-threaded hbus->wq, so there is not a double-remove issue for the
slot. Note 2: we can't offload hv_pci_eject_device() from
hv_pci_onchannelcallback() to the workqueue, because we need
hv_pci_onchannelcallback() synchronously call hv_pci_eject_device() to
poll the channel's ringbuffer to work around the
"hangs in hv_compose_msi_msg()" issue: see
commit de0aa7b2f97d ("PCI: hv: Fix 2 hang issues in hv_compose_msi_msg()")

Fixes: a15f2c08c708 ("PCI: hv: support reporting serial number as slot information")
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Cc: stable@vger.kernel.org
---
 drivers/pci/controller/pci-hyperv.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index b489412e3502..82acd6155adf 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -1776,6 +1776,10 @@ static void pci_devices_present_work(struct work_struct *work)
 		hpdev = list_first_entry(&removed, struct hv_pci_dev,
 					 list_entry);
 		list_del(&hpdev->list_entry);
+
+		if (hpdev->pci_slot)
+			pci_destroy_slot(hpdev->pci_slot);
+
 		put_pcichild(hpdev);
 	}
 
-- 
2.19.1


  parent reply index

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-04 21:34 [PATCH 0/3] pci-hyperv: fix memory leak and add pci_destroy_slot() Dexuan Cui
2019-03-04 21:34 ` [PATCH 1/3] PCI: hv: Fix a memory leak in hv_eject_device_work() Dexuan Cui
2019-03-20 21:37   ` Michael Kelley
2019-03-21  0:12     ` Dexuan Cui
2019-03-26 17:08       ` Lorenzo Pieralisi
2019-03-26 17:47         ` Michael Kelley
2019-03-26 18:01           ` Dexuan Cui
2019-03-26 18:12             ` Lorenzo Pieralisi
2019-03-04 21:34 ` [PATCH 2/3] PCI: hv: Add hv_pci_remove_slots() when we unload the driver Dexuan Cui
2019-03-20 21:38   ` Michael Kelley
2019-03-04 21:34 ` Dexuan Cui [this message]
2019-03-20 21:44   ` [PATCH 3/3] PCI: hv: Add pci_destroy_slot() in pci_devices_present_work(), if necessary Michael Kelley
2019-03-21  0:35     ` Dexuan Cui
2019-03-21  0:42       ` Dexuan Cui
2019-03-26 17:50       ` Michael Kelley
2019-03-26 19:54   ` Lorenzo Pieralisi
2019-03-27  0:22     ` Dexuan Cui
2019-03-05 18:27 ` [PATCH 0/3] pci-hyperv: fix memory leak and add pci_destroy_slot() Stephen Hemminger

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