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Date: Tue, 28 Mar 2023 06:33:07 +0000
From: Dexuan Cui <decui@...rosoft.com>
To: "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
"davem@...emloft.net" <davem@...emloft.net>,
"edumazet@...gle.com" <edumazet@...gle.com>,
Haiyang Zhang <haiyangz@...rosoft.com>,
Jake Oshins <jakeo@...rosoft.com>,
"kuba@...nel.org" <kuba@...nel.org>, "kw@...ux.com" <kw@...ux.com>,
KY Srinivasan <kys@...rosoft.com>,
"leon@...nel.org" <leon@...nel.org>,
"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
"lpieralisi@...nel.org" <lpieralisi@...nel.org>,
"Michael Kelley (LINUX)" <mikelley@...rosoft.com>,
"pabeni@...hat.com" <pabeni@...hat.com>,
"robh@...nel.org" <robh@...nel.org>,
"saeedm@...dia.com" <saeedm@...dia.com>,
"wei.liu@...nel.org" <wei.liu@...nel.org>,
Long Li <longli@...rosoft.com>,
"boqun.feng@...il.com" <boqun.feng@...il.com>,
Wei Hu <weh@...rosoft.com>
CC: "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH 4/6] Revert "PCI: hv: Fix a timing issue which causes
kdump to fail occasionally"
> From: Dexuan Cui <decui@...rosoft.com>
> Sent: Monday, March 27, 2023 9:51 PM
> To: bhelgaas@...gle.com; davem@...emloft.net; Dexuan Cui
> <decui@...rosoft.com>; edumazet@...gle.com; Haiyang Zhang
> <haiyangz@...rosoft.com>; Jake Oshins <jakeo@...rosoft.com>;
> kuba@...nel.org; kw@...ux.com; KY Srinivasan <kys@...rosoft.com>;
> leon@...nel.org; linux-pci@...r.kernel.org; lpieralisi@...nel.org; Michael
> Kelley (LINUX) <mikelley@...rosoft.com>; pabeni@...hat.com;
> robh@...nel.org; saeedm@...dia.com; wei.liu@...nel.org; Long Li
> <longli@...rosoft.com>; boqun.feng@...il.com
> Cc: linux-hyperv@...r.kernel.org; linux-kernel@...r.kernel.org;
> linux-rdma@...r.kernel.org; netdev@...r.kernel.org
> Subject: [PATCH 4/6] Revert "PCI: hv: Fix a timing issue which causes kdump to
> fail occasionally"
>
> 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@...rosoft.com>
> ---
> drivers/pci/controller/pci-hyperv.c | 71 ++++++++++++++---------------
> 1 file changed, 34 insertions(+), 37 deletions(-)
>
> diff --git a/drivers/pci/controller/pci-hyperv.c
> b/drivers/pci/controller/pci-hyperv.c
> index 46df6d093d68..48feab095a14 100644
> --- a/drivers/pci/controller/pci-hyperv.c
> +++ b/drivers/pci/controller/pci-hyperv.c
> @@ -3225,8 +3225,10 @@ 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
> @@ -3253,6 +3255,38 @@ 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",
> @@ -3493,7 +3527,6 @@ 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;
>
> /*
> @@ -3633,47 +3666,11 @@ 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;
>
> --
> 2.25.1
+ Wei Hu.
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