[PATCH 1/3] PCI: hv: fix a comment typo in _hv_pcifront_read_config()

[PATCH 1/3] PCI: hv: fix a comment typo in _hv_pcifront_read_config()

[Dexuan Cui]

No functional change.

Signed-off-by: Dexuan Cui <decui@microsoft.com>
Fixes: bdd74440d9e8 ("PCI: hv: Add explicit barriers to config space access=
")
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: stable@vger.kernel.org
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: K. Y. Srinivasan <kys@microsoft.com>
---
 drivers/pci/host/pci-hyperv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c
index 2faf38eab785..1233300f41c6 100644
--- a/drivers/pci/host/pci-hyperv.c
+++ b/drivers/pci/host/pci-hyperv.c
@@ -653,7 +653,7 @@ static void _hv_pcifront_read_config(struct hv_pci_dev =
*hpdev, int where,
 			break;
 		}
 		/*
-		 * Make sure the write was done before we release the spinlock
+		 * Make sure the read was done before we release the spinlock
 		 * allowing consecutive reads/writes.
 		 */
 		mb();
--=20
2.7.4

[PATCH 2/3] PCI: hv: serialize the present/eject work items

[Dexuan Cui]

When we hot-remove the device, we first receive a PCI_EJECT message and
then receive a PCI_BUS_RELATIONS message with bus_rel->device_count =3D=3D =
0.

The first message is offloaded to hv_eject_device_work(), and the second
is offloaded to pci_devices_present_work(). Both the paths can be running
list_del(&hpdev->list_entry), causing general protection fault, because
system_wq can run them concurrently.

The patch eliminates the race condition.

Signed-off-by: Dexuan Cui <decui@microsoft.com>
Tested-by: Adrian Suhov <v-adsuho@microsoft.com>
Tested-by: Chris Valean <v-chvale@microsoft.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Jack Morgenstein <jackm@mellanox.com>
Cc: stable@vger.kernel.org
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: K. Y. Srinivasan <kys@microsoft.com>
---
 drivers/pci/host/pci-hyperv.c | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c
index 1233300f41c6..57b1fb3ebdb9 100644
--- a/drivers/pci/host/pci-hyperv.c
+++ b/drivers/pci/host/pci-hyperv.c
@@ -461,6 +461,8 @@ struct hv_pcibus_device {
 	struct retarget_msi_interrupt retarget_msi_interrupt_params;
=20
 	spinlock_t retarget_msi_interrupt_lock;
+
+	struct workqueue_struct *wq;
 };
=20
 /*
@@ -1770,7 +1772,7 @@ static void hv_pci_devices_present(struct hv_pcibus_d=
evice *hbus,
 	spin_unlock_irqrestore(&hbus->device_list_lock, flags);
=20
 	get_hvpcibus(hbus);
-	schedule_work(&dr_wrk->wrk);
+	queue_work(hbus->wq, &dr_wrk->wrk);
 }
=20
 /**
@@ -1848,7 +1850,7 @@ static void hv_pci_eject_device(struct hv_pci_dev *hp=
dev)
 	get_pcichild(hpdev, hv_pcidev_ref_pnp);
 	INIT_WORK(&hpdev->wrk, hv_eject_device_work);
 	get_hvpcibus(hpdev->hbus);
-	schedule_work(&hpdev->wrk);
+	queue_work(hpdev->hbus->wq, &hpdev->wrk);
 }
=20
 /**
@@ -2463,11 +2465,17 @@ static int hv_pci_probe(struct hv_device *hdev,
 	spin_lock_init(&hbus->retarget_msi_interrupt_lock);
 	sema_init(&hbus->enum_sem, 1);
 	init_completion(&hbus->remove_event);
+	hbus->wq =3D alloc_ordered_workqueue("hv_pci_%x", 0,
+					   hbus->sysdata.domain);
+	if (!hbus->wq) {
+		ret =3D -ENOMEM;
+		goto free_bus;
+	}
=20
 	ret =3D vmbus_open(hdev->channel, pci_ring_size, pci_ring_size, NULL, 0,
 			 hv_pci_onchannelcallback, hbus);
 	if (ret)
-		goto free_bus;
+		goto destroy_wq;
=20
 	hv_set_drvdata(hdev, hbus);
=20
@@ -2536,6 +2544,9 @@ static int hv_pci_probe(struct hv_device *hdev,
 	hv_free_config_window(hbus);
 close:
 	vmbus_close(hdev->channel);
+destroy_wq:
+	drain_workqueue(hbus->wq);
+	destroy_workqueue(hbus->wq);
 free_bus:
 	free_page((unsigned long)hbus);
 	return ret;
@@ -2615,6 +2626,8 @@ static int hv_pci_remove(struct hv_device *hdev)
 	irq_domain_free_fwnode(hbus->sysdata.fwnode);
 	put_hvpcibus(hbus);
 	wait_for_completion(&hbus->remove_event);
+	drain_workqueue(hbus->wq);
+	destroy_workqueue(hbus->wq);
 	free_page((unsigned long)hbus);
 	return 0;
 }
--=20
2.7.4

RE: [PATCH 2/3] PCI: hv: serialize the present/eject work items

[Michael Kelley (EOSG)]

> -----Original Message-----
> From: linux-kernel-owner@vger.kernel.org <linux-kernel-owner@vger.kernel.=
org> On Behalf
> Of Dexuan Cui
> Sent: Friday, March 2, 2018 4:21 PM
> To: bhelgaas@google.com; linux-pci@vger.kernel.org; KY Srinivasan <kys@mi=
crosoft.com>;
> Stephen Hemminger <sthemmin@microsoft.com>
> Cc: linux-kernel@vger.kernel.org; driverdev-devel@linuxdriverproject.org;=
 Haiyang Zhang
> <haiyangz@microsoft.com>; olaf@aepfle.de; apw@canonical.com; jasowang@red=
hat.com;
> vkuznets@redhat.com; marcelo.cerri@canonical.com; Dexuan Cui <decui@micro=
soft.com>;
> Jack Morgenstein <jackm@mellanox.com>; stable@vger.kernel.org
> Subject: [PATCH 2/3] PCI: hv: serialize the present/eject work items
>=20
> When we hot-remove the device, we first receive a PCI_EJECT message and
> then receive a PCI_BUS_RELATIONS message with bus_rel->device_count =3D=
=3D 0.
>=20
> The first message is offloaded to hv_eject_device_work(), and the second
> is offloaded to pci_devices_present_work(). Both the paths can be running
> list_del(&hpdev->list_entry), causing general protection fault, because
> system_wq can run them concurrently.
>=20
> The patch eliminates the race condition.

With this patch, the enum_sem field in struct hv_pcibus_device
is no longer needed.  The semaphore serializes execution in
hv_pci_devices_present_work(), and that serialization is now done
with the ordered workqueue.  Also, the last paragraph of the top level
comment for hv_pci_devices_present_work() should be updated to
reflect the new ordering assumptions.

Separately, an unrelated bug:  At the top of hv_eject_device_work(),
the first test may do a put_pcichild() and return.  This exit path also
needs to do put_hvpcibus() to balance the ref counts, or do a goto
the last two lines at the bottom of the function.

>=20
> Signed-off-by: Dexuan Cui <decui@microsoft.com>
> Tested-by: Adrian Suhov <v-adsuho@microsoft.com>
> Tested-by: Chris Valean <v-chvale@microsoft.com>
> Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
> Cc: Jack Morgenstein <jackm@mellanox.com>
> Cc: stable@vger.kernel.org
> Cc: Stephen Hemminger <sthemmin@microsoft.com>
> Cc: K. Y. Srinivasan <kys@microsoft.com>
> ---
>  drivers/pci/host/pci-hyperv.c | 19 ++++++++++++++++---
>  1 file changed, 16 insertions(+), 3 deletions(-)
>=20
> diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.=
c
> index 1233300f41c6..57b1fb3ebdb9 100644
> --- a/drivers/pci/host/pci-hyperv.c
> +++ b/drivers/pci/host/pci-hyperv.c
> @@ -461,6 +461,8 @@ struct hv_pcibus_device {
>  	struct retarget_msi_interrupt retarget_msi_interrupt_params;
>=20
>  	spinlock_t retarget_msi_interrupt_lock;
> +
> +	struct workqueue_struct *wq;
>  };
>=20
>  /*
> @@ -1770,7 +1772,7 @@ static void hv_pci_devices_present(struct hv_pcibus=
_device *hbus,
>  	spin_unlock_irqrestore(&hbus->device_list_lock, flags);
>=20
>  	get_hvpcibus(hbus);
> -	schedule_work(&dr_wrk->wrk);
> +	queue_work(hbus->wq, &dr_wrk->wrk);

This invocation of get_hvpcibus() and queue_work() could be made
conditional on whether the preceding list_add_tail() transitioned
the list from empty to non-empty.  If the list was already non-empty,
a previously queued invocation of hv_pci_devices_present_work()
will find the new entry and process it.   But this is an
optimization in a non-perf sensitive code path, so may not be
worth it.

>  }
>=20
>  /**
> @@ -1848,7 +1850,7 @@ static void hv_pci_eject_device(struct hv_pci_dev *=
hpdev)
>  	get_pcichild(hpdev, hv_pcidev_ref_pnp);
>  	INIT_WORK(&hpdev->wrk, hv_eject_device_work);
>  	get_hvpcibus(hpdev->hbus);
> -	schedule_work(&hpdev->wrk);
> +	queue_work(hpdev->hbus->wq, &hpdev->wrk);
>  }
>=20
>  /**
> @@ -2463,11 +2465,17 @@ static int hv_pci_probe(struct hv_device *hdev,
>  	spin_lock_init(&hbus->retarget_msi_interrupt_lock);
>  	sema_init(&hbus->enum_sem, 1);
>  	init_completion(&hbus->remove_event);
> +	hbus->wq =3D alloc_ordered_workqueue("hv_pci_%x", 0,
> +					   hbus->sysdata.domain);
> +	if (!hbus->wq) {
> +		ret =3D -ENOMEM;
> +		goto free_bus;
> +	}
>=20
>  	ret =3D vmbus_open(hdev->channel, pci_ring_size, pci_ring_size, NULL, 0=
,
>  			 hv_pci_onchannelcallback, hbus);
>  	if (ret)
> -		goto free_bus;
> +		goto destroy_wq;
>=20
>  	hv_set_drvdata(hdev, hbus);
>=20
> @@ -2536,6 +2544,9 @@ static int hv_pci_probe(struct hv_device *hdev,
>  	hv_free_config_window(hbus);
>  close:
>  	vmbus_close(hdev->channel);
> +destroy_wq:
> +	drain_workqueue(hbus->wq);

The drain_workqueue() call isn't necessary.  destroy_workqueue() calls
drain_workqueue() and there better not be anything in the workqueue
anyway since all the ref counts are zero.

> +	destroy_workqueue(hbus->wq);
>  free_bus:
>  	free_page((unsigned long)hbus);
>  	return ret;
> @@ -2615,6 +2626,8 @@ static int hv_pci_remove(struct hv_device *hdev)
>  	irq_domain_free_fwnode(hbus->sysdata.fwnode);
>  	put_hvpcibus(hbus);
>  	wait_for_completion(&hbus->remove_event);
> +	drain_workqueue(hbus->wq);

Same here -- drain_workqueue() isn't needed.  The workqueue
must be empty anyway since the remove_event has completed
and the ref counts will all be zero.

> +	destroy_workqueue(hbus->wq);
>  	free_page((unsigned long)hbus);
>  	return 0;
>  }
> --
> 2.7.4

RE: [PATCH 2/3] PCI: hv: serialize the present/eject work items

[Dexuan Cui]

> From: Michael Kelley (EOSG)
> Sent: Saturday, March 3, 2018 08:10
> > From: linux-kernel-owner@vger.kernel.org <linux-kernel-
> owner@vger.kernel.org> On Behalf Of Dexuan Cui
> > Sent: Friday, March 2, 2018 4:21 PM
> > When we hot-remove the device, we first receive a PCI_EJECT message and
> > then receive a PCI_BUS_RELATIONS message with bus_rel->device_count =3D=
=3D
> 0.
> >
> > The first message is offloaded to hv_eject_device_work(), and the secon=
d
> > is offloaded to pci_devices_present_work(). Both the paths can be runni=
ng
> > list_del(&hpdev->list_entry), causing general protection fault, because
> > system_wq can run them concurrently.
> >
> > The patch eliminates the race condition.
>=20
> With this patch, the enum_sem field in struct hv_pcibus_device
> is no longer needed.  The semaphore serializes execution in
> hv_pci_devices_present_work(), and that serialization is now done
> with the ordered workqueue.  Also, the last paragraph of the top level
> comment for hv_pci_devices_present_work() should be updated to
> reflect the new ordering assumptions.

Thanks! I'll make an extra patch for this.

> Separately, an unrelated bug:  At the top of hv_eject_device_work(),
> the first test may do a put_pcichild() and return.  This exit path also
> needs to do put_hvpcibus() to balance the ref counts, or do a goto
> the last two lines at the bottom of the function.

When we're in hv_eject_device_work(), IMO hpdev->state must be=20
hv_pcichild_ejecting, so I'm going to make a patch like this:

@@ -1867,10 +1867,7 @@ static void hv_eject_device_work(struct work_struct =
*work)

        hpdev =3D container_of(work, struct hv_pci_dev, wrk);

-       if (hpdev->state !=3D hv_pcichild_ejecting) {
-               put_pcichild(hpdev, hv_pcidev_ref_pnp);
-               return;
-       }
+       WARN_ON(hpdev->state !=3D hv_pcichild_ejecting);

        /*
         * Ejection can come before or after the PCI bus has been set up, s=
o
=20
> > @@ -1770,7 +1772,7 @@ static void hv_pci_devices_present(struct
> hv_pcibus_device *hbus,
> >  	spin_unlock_irqrestore(&hbus->device_list_lock, flags);
> >
> >  	get_hvpcibus(hbus);
> > -	schedule_work(&dr_wrk->wrk);
> > +	queue_work(hbus->wq, &dr_wrk->wrk);
>=20
> This invocation of get_hvpcibus() and queue_work() could be made
> conditional on whether the preceding list_add_tail() transitioned
> the list from empty to non-empty.  If the list was already non-empty,
> a previously queued invocation of hv_pci_devices_present_work()
> will find the new entry and process it.   But this is an
> optimization in a non-perf sensitive code path, so may not be
> worth it.

Exactly. I'll add the the optimization.

> > @@ -1848,7 +1850,7 @@ static void hv_pci_eject_device(struct hv_pci_dev
> *hpdev)
> >  	get_pcichild(hpdev, hv_pcidev_ref_pnp);
> >  	INIT_WORK(&hpdev->wrk, hv_eject_device_work);
> >  	get_hvpcibus(hpdev->hbus);
> > -	schedule_work(&hpdev->wrk);
> > +	queue_work(hpdev->hbus->wq, &hpdev->wrk);
> >  }
> >
> >  /**
> > @@ -2463,11 +2465,17 @@ static int hv_pci_probe(struct hv_device *hdev,
> >  	spin_lock_init(&hbus->retarget_msi_interrupt_lock);
> >  	sema_init(&hbus->enum_sem, 1);
> >  	init_completion(&hbus->remove_event);
> > +	hbus->wq =3D alloc_ordered_workqueue("hv_pci_%x", 0,
> > +					   hbus->sysdata.domain);
> > +	if (!hbus->wq) {
> > +		ret =3D -ENOMEM;
> > +		goto free_bus;
> > +	}
> >
> >  	ret =3D vmbus_open(hdev->channel, pci_ring_size, pci_ring_size, NULL,=
 0,
> >  			 hv_pci_onchannelcallback, hbus);
> >  	if (ret)
> > -		goto free_bus;
> > +		goto destroy_wq;
> >
> >  	hv_set_drvdata(hdev, hbus);
> >
> > @@ -2536,6 +2544,9 @@ static int hv_pci_probe(struct hv_device *hdev,
> >  	hv_free_config_window(hbus);
> >  close:
> >  	vmbus_close(hdev->channel);
> > +destroy_wq:
> > +	drain_workqueue(hbus->wq);
>=20
> The drain_workqueue() call isn't necessary.  destroy_workqueue() calls
> drain_workqueue() and there better not be anything in the workqueue
> anyway since all the ref counts are zero.

OK. Will remove it.

> > +	destroy_workqueue(hbus->wq);
> >  free_bus:
> >  	free_page((unsigned long)hbus);
> >  	return ret;
> > @@ -2615,6 +2626,8 @@ static int hv_pci_remove(struct hv_device *hdev)
> >  	irq_domain_free_fwnode(hbus->sysdata.fwnode);
> >  	put_hvpcibus(hbus);
> >  	wait_for_completion(&hbus->remove_event);
> > +	drain_workqueue(hbus->wq);
>=20
> Same here -- drain_workqueue() isn't needed.  The workqueue
> must be empty anyway since the remove_event has completed
> and the ref counts will all be zero.

Will remove it.

> > +	destroy_workqueue(hbus->wq);

I'm going to post a v2 patchset tomorrow.

Thanks,
-- Dexuan

[PATCH 3/3] PCI: hv: fix 2 hang issues in hv_compose_msi_msg()

[Dexuan Cui]

1. With the patch "x86/vector/msi: Switch to global reservation mode"
(4900be8360), the recent v4.15 and newer kernels always hang for 1-vCPU
Hyper-V VM with SR-IOV. This is because when we reach hv_compose_msi_msg()
by request_irq()  -> request_threaded_irq() -> __setup_irq()->irq_startup()
 -> __irq_startup() -> irq_domain_activate_irq() -> ... ->
msi_domain_activate() -> ... -> hv_compose_msi_msg(), local irq is
disabled in __setup_irq().

Fix this by polling the channel.

2. If the host is ejecting the VF device before we reach
hv_compose_msi_msg(), in a UP VM, we can hang in hv_compose_msi_msg()
forever, because at this time the host doesn't respond to the
CREATE_INTERRUPT request. This issue also happens to old kernels like
v4.14, v4.13, etc.

Fix this by polling the channel for the PCI_EJECT message and
hpdev->state, and by checking the PCI vendor ID.

Note: actually the above issues also happen to a SMP VM, if
"hbus->hdev->channel->target_cpu =3D=3D smp_processor_id()" is true.

Signed-off-by: Dexuan Cui <decui@microsoft.com>
Tested-by: Adrian Suhov <v-adsuho@microsoft.com>
Tested-by: Chris Valean <v-chvale@microsoft.com>
Cc: stable@vger.kernel.org
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Jack Morgenstein <jackm@mellanox.com>
---
 drivers/pci/host/pci-hyperv.c | 58 +++++++++++++++++++++++++++++++++++++++=
+++-
 1 file changed, 57 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c
index 57b1fb3ebdb9..32d6b03cdd40 100644
--- a/drivers/pci/host/pci-hyperv.c
+++ b/drivers/pci/host/pci-hyperv.c
@@ -522,6 +522,8 @@ struct hv_pci_compl {
 	s32 completion_status;
 };
=20
+static void hv_pci_onchannelcallback(void *context);
+
 /**
  * hv_pci_generic_compl() - Invoked for a completion packet
  * @context:		Set up by the sender of the packet.
@@ -666,6 +668,31 @@ static void _hv_pcifront_read_config(struct hv_pci_dev=
 *hpdev, int where,
 	}
 }
=20
+static u16 hv_pcifront_get_vendor_id(struct hv_pci_dev *hpdev)
+{
+	u16 ret;
+	unsigned long flags;
+	void __iomem *addr =3D hpdev->hbus->cfg_addr + CFG_PAGE_OFFSET +
+			     PCI_VENDOR_ID;
+
+	spin_lock_irqsave(&hpdev->hbus->config_lock, flags);
+
+	/* Choose the function to be read. (See comment above) */
+	writel(hpdev->desc.win_slot.slot, hpdev->hbus->cfg_addr);
+	/* Make sure the function was chosen before we start reading. */
+	mb();
+	/* Read from that function's config space. */
+	ret =3D readw(addr);
+	/*
+	 * mb() is not required here, because the spin_unlock_irqrestore()
+	 * is a barrier.
+	 */
+
+	spin_unlock_irqrestore(&hpdev->hbus->config_lock, flags);
+
+	return ret;
+}
+
 /**
  * _hv_pcifront_write_config() - Internal PCI config write
  * @hpdev:	The PCI driver's representation of the device
@@ -1108,8 +1135,37 @@ static void hv_compose_msi_msg(struct irq_data *data=
, struct msi_msg *msg)
 	 * Since this function is called with IRQ locks held, can't
 	 * do normal wait for completion; instead poll.
 	 */
-	while (!try_wait_for_completion(&comp.comp_pkt.host_event))
+	while (!try_wait_for_completion(&comp.comp_pkt.host_event)) {
+		/* 0xFFFF means an invalid PCI VENDOR ID. */
+		if (hv_pcifront_get_vendor_id(hpdev) =3D=3D 0xFFFF) {
+			dev_err_once(&hbus->hdev->device,
+				     "the device has gone\n");
+			goto free_int_desc;
+		}
+
+		/*
+		 * When the higher level interrupt code calls us with
+		 * interrupt disabled, we must poll the channel by calling
+		 * the channel callback directly when channel->target_cpu is
+		 * the current CPU. When the higher level interrupt code
+		 * calls us with interrupt enabled, let's add the
+		 * local_bh_disable()/enable() to avoid race.
+		 */
+		local_bh_disable();
+
+		if (hbus->hdev->channel->target_cpu =3D=3D smp_processor_id())
+			hv_pci_onchannelcallback(hbus);
+
+		local_bh_enable();
+
+		if (hpdev->state =3D=3D hv_pcichild_ejecting) {
+			dev_err_once(&hbus->hdev->device,
+				     "the device is being ejected\n");
+			goto free_int_desc;
+		}
+
 		udelay(100);
+	}
=20
 	if (comp.comp_pkt.completion_status < 0) {
 		dev_err(&hbus->hdev->device,
--=20
2.7.4