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Message-ID: <SA1PR21MB13356A77700580DF0C742856BF889@SA1PR21MB1335.namprd21.prod.outlook.com> 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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