Linux-HyperV Archive on lore.kernel.org
 help / color / Atom feed
From: Wei Hu <weh@microsoft.com>
To: kys@microsoft.com, haiyangz@microsoft.com,
	sthemmin@microsoft.com, wei.liu@kernel.org,
	lorenzo.pieralisi@arm.com, robh@kernel.org, bhelgaas@google.com,
	linux-hyperv@vger.kernel.org, linux-pci@vger.kernel.org,
	linux-kernel@vger.kernel.org, decui@microsoft.com,
	mikelley@microsoft.com
Cc: Wei Hu <weh@microsoft.com>
Subject: [PATCH v4] PCI: hv: Fix a timing issue which causes kdump to fail occasionally
Date: Mon, 27 Jul 2020 15:17:31 +0800
Message-ID: <20200727071731.18516-1-weh@microsoft.com> (raw)

Kdump could fail sometime on Hyper-V guest over Accelerated Network
interface. This is because the retry in hv_pci_enter_d0() releases
child device strurctures in hv_pci_bus_exit(). Although there is
a second asynchronous device relations message sending from the host,
if this message arrives guest after hv_send_resource_allocated() is
called, the retry would fail.

Fix the problem by moving retry to hv_pci_probe() and starting retry
from hv_pci_query_relations() call.  This will cause a device relations
message to arrive guest synchronously.  The guest would be able to
rebuild the child device structures before calling
hv_send_resource_allocated().

This problem only happens on Accelerated Network or SRIOV devices as
only such devices currently are attached under vmbus PCI bridge.

Fixes: c81992e7f4aa ("PCI: hv: Retry PCI bus D0 entry on invalid device state")
Signed-off-by: Wei Hu <weh@microsoft.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
---
    v2: Adding Fixes tag according to Michael Kelley's review comment.
    v3: Fix couple typos and reword commit message to make it clearer.
    Thanks the comments from Bjorn Helgaas.
    v4: Adding more  problem descritpions in the commit message
    and code upon request from Lorenze Pieralisi.

 drivers/pci/controller/pci-hyperv.c | 71 +++++++++++++++--------------
 1 file changed, 37 insertions(+), 34 deletions(-)

diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index bf40ff09c99d..d1758986fbc9 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -2759,10 +2759,8 @@ static int hv_pci_enter_d0(struct hv_device *hdev)
 	struct pci_bus_d0_entry *d0_entry;
 	struct hv_pci_compl comp_pkt;
 	struct pci_packet *pkt;
-	bool retry = true;
 	int ret;
 
-enter_d0_retry:
 	/*
 	 * Tell the host that the bus is ready to use, and moved into the
 	 * powered-on state.  This includes telling the host which region
@@ -2789,38 +2787,6 @@ static int hv_pci_enter_d0(struct hv_device *hdev)
 	if (ret)
 		goto exit;
 
-	/*
-	 * In certain case (Kdump) the pci device of interest was
-	 * not cleanly shut down and resource is still held on host
-	 * side, the host could return invalid device status.
-	 * We need to explicitly request host to release the resource
-	 * and try to enter D0 again.
-	 */
-	if (comp_pkt.completion_status < 0 && retry) {
-		retry = false;
-
-		dev_err(&hdev->device, "Retrying D0 Entry\n");
-
-		/*
-		 * Hv_pci_bus_exit() calls hv_send_resource_released()
-		 * to free up resources of its child devices.
-		 * In the kdump kernel we need to set the
-		 * wslot_res_allocated to 255 so it scans all child
-		 * devices to release resources allocated in the
-		 * normal kernel before panic happened.
-		 */
-		hbus->wslot_res_allocated = 255;
-
-		ret = hv_pci_bus_exit(hdev, true);
-
-		if (ret == 0) {
-			kfree(pkt);
-			goto enter_d0_retry;
-		}
-		dev_err(&hdev->device,
-			"Retrying D0 failed with ret %d\n", ret);
-	}
-
 	if (comp_pkt.completion_status < 0) {
 		dev_err(&hdev->device,
 			"PCI Pass-through VSP failed D0 Entry with status %x\n",
@@ -3058,6 +3024,7 @@ static int hv_pci_probe(struct hv_device *hdev,
 	struct hv_pcibus_device *hbus;
 	u16 dom_req, dom;
 	char *name;
+	bool enter_d0_retry = true;
 	int ret;
 
 	/*
@@ -3178,11 +3145,47 @@ static int hv_pci_probe(struct hv_device *hdev,
 	if (ret)
 		goto free_fwnode;
 
+retry:
 	ret = hv_pci_query_relations(hdev);
 	if (ret)
 		goto free_irq_domain;
 
 	ret = hv_pci_enter_d0(hdev);
+	/*
+	 * In certain case (Kdump) the pci device of interest was
+	 * not cleanly shut down and resource is still held on host
+	 * side, the host could return invalid device status.
+	 * We need to explicitly request host to release the resource
+	 * and try to enter D0 again.
+	 * Since the hv_pci_bus_exit() call releases structures
+	 * of all its child devices, we need to start the retry from
+	 * hv_pci_query_relations() call, requesting host to send
+	 * the synchronous child device relations message before this
+	 * information is needed in hv_send_resources_allocated()
+	 * call later .
+	 */
+	if (ret == -EPROTO && enter_d0_retry) {
+		enter_d0_retry = false;
+
+		dev_err(&hdev->device, "Retrying D0 Entry\n");
+
+		/*
+		 * Hv_pci_bus_exit() calls hv_send_resources_released()
+		 * to free up resources of its child devices.
+		 * In the kdump kernel we need to set the
+		 * wslot_res_allocated to 255 so it scans all child
+		 * devices to release resources allocated in the
+		 * normal kernel before panic happened.
+		 */
+		hbus->wslot_res_allocated = 255;
+		ret = hv_pci_bus_exit(hdev, true);
+
+		if (ret == 0)
+			goto retry;
+
+		dev_err(&hdev->device,
+			"Retrying D0 failed with ret %d\n", ret);
+	}
 	if (ret)
 		goto free_irq_domain;
 
-- 
2.20.1


             reply index

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-27  7:17 Wei Hu [this message]
2020-07-27 11:18 ` Lorenzo Pieralisi
2020-07-27 12:10   ` Wei Hu

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200727071731.18516-1-weh@microsoft.com \
    --to=weh@microsoft.com \
    --cc=bhelgaas@google.com \
    --cc=decui@microsoft.com \
    --cc=haiyangz@microsoft.com \
    --cc=kys@microsoft.com \
    --cc=linux-hyperv@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-pci@vger.kernel.org \
    --cc=lorenzo.pieralisi@arm.com \
    --cc=mikelley@microsoft.com \
    --cc=robh@kernel.org \
    --cc=sthemmin@microsoft.com \
    --cc=wei.liu@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-HyperV Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-hyperv/0 linux-hyperv/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-hyperv linux-hyperv/ https://lore.kernel.org/linux-hyperv \
		linux-hyperv@vger.kernel.org
	public-inbox-index linux-hyperv

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-hyperv


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git