Patch "Revert "PCI: hv: Fix a timing issue which causes kdump to fail occasionally"" has been added to the 5.10-stable tree

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This is a note to let you know that I've just added the patch titled

    Revert "PCI: hv: Fix a timing issue which causes kdump to fail occasionally"

to the 5.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     revert-pci-hv-fix-a-timing-issue-which-causes-kdump-to-fail-occasionally.patch
and it can be found in the queue-5.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From a847234e24d03d01a9566d1d9dcce018cc018d67 Mon Sep 17 00:00:00 2001
From: Dexuan Cui <decui@xxxxxxxxxxxxx>
Date: Wed, 14 Jun 2023 21:44:50 -0700
Subject: Revert "PCI: hv: Fix a timing issue which causes kdump to fail occasionally"

From: Dexuan Cui <decui@xxxxxxxxxxxxx>

commit a847234e24d03d01a9566d1d9dcce018cc018d67 upstream.

This reverts commit d6af2ed29c7c1c311b96dac989dcb991e90ee195.

The statement "the hv_pci_bus_exit() call releases structures of all its
child devices" in commit d6af2ed29c7c is not true: in the path
hv_pci_probe() -> hv_pci_enter_d0() -> hv_pci_bus_exit(hdev, true): the
parameter "keep_devs" is true, so hv_pci_bus_exit() does *not* release the
child "struct hv_pci_dev *hpdev" that is created earlier in
pci_devices_present_work() -> new_pcichild_device().

The commit d6af2ed29c7c was originally made in July 2020 for RHEL 7.7,
where the old version of hv_pci_bus_exit() was used; when the commit was
rebased and merged into the upstream, people didn't notice that it's
not really necessary. The commit itself doesn't cause any issue, but it
makes hv_pci_probe() more complicated. Revert it to facilitate some
upcoming changes to hv_pci_probe().

Signed-off-by: Dexuan Cui <decui@xxxxxxxxxxxxx>
Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
Acked-by: Wei Hu <weh@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/20230615044451.5580-5-decui@xxxxxxxxxxxxx
Signed-off-by: Wei Liu <wei.liu@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/pci/controller/pci-hyperv.c |   71 +++++++++++++++++-------------------
 1 file changed, 34 insertions(+), 37 deletions(-)

--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -2842,8 +2842,10 @@ static int hv_pci_enter_d0(struct hv_dev
 	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
@@ -2870,6 +2872,38 @@ static int hv_pci_enter_d0(struct hv_dev
 	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",
@@ -3125,7 +3159,6 @@ static int hv_pci_probe(struct hv_device
 	struct hv_pcibus_device *hbus;
 	u16 dom_req, dom;
 	char *name;
-	bool enter_d0_retry = true;
 	int ret;
 
 	/*
@@ -3246,47 +3279,11 @@ static int hv_pci_probe(struct hv_device
 	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;
 


Patches currently in stable-queue which might be from decui@xxxxxxxxxxxxx are

queue-5.10/pci-hv-fix-a-race-condition-in-hv_irq_unmask-that-can-cause-panic.patch
queue-5.10/revert-pci-hv-fix-a-timing-issue-which-causes-kdump-to-fail-occasionally.patch
queue-5.10/pci-hv-remove-the-useless-hv_pcichild_state-from-struct-hv_pci_dev.patch
queue-5.10/pci-hv-fix-a-race-condition-bug-in-hv_pci_query_relations.patch



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