| Message ID | 20230328045122.25850-5-decui@microsoft.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | pci-hyper: fix race condition bugs for fast device hotplug | expand |
| Context | Check | Description |
|---|---|---|
| netdev/tree_selection | success | Not a local patch |
> From: Dexuan Cui <decui@microsoft.com> > Sent: Monday, March 27, 2023 9:51 PM > To: bhelgaas@google.com; davem@davemloft.net; Dexuan Cui > <decui@microsoft.com>; edumazet@google.com; Haiyang Zhang > <haiyangz@microsoft.com>; Jake Oshins <jakeo@microsoft.com>; > kuba@kernel.org; kw@linux.com; KY Srinivasan <kys@microsoft.com>; > leon@kernel.org; linux-pci@vger.kernel.org; lpieralisi@kernel.org; Michael > Kelley (LINUX) <mikelley@microsoft.com>; pabeni@redhat.com; > robh@kernel.org; saeedm@nvidia.com; wei.liu@kernel.org; Long Li > <longli@microsoft.com>; boqun.feng@gmail.com > Cc: linux-hyperv@vger.kernel.org; linux-kernel@vger.kernel.org; > linux-rdma@vger.kernel.org; netdev@vger.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 The commit d6af2ed29c7c was originally made in July 2020 for RHEL 7.7, 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@microsoft.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.
> -----Original Message----- > From: Dexuan Cui <decui@microsoft.com> > Sent: Tuesday, March 28, 2023 2:33 PM > To: bhelgaas@google.com; davem@davemloft.net; edumazet@google.com; > Haiyang Zhang <haiyangz@microsoft.com>; Jake Oshins > <jakeo@microsoft.com>; kuba@kernel.org; kw@linux.com; KY Srinivasan > <kys@microsoft.com>; leon@kernel.org; linux-pci@vger.kernel.org; > lpieralisi@kernel.org; Michael Kelley (LINUX) <mikelley@microsoft.com>; > pabeni@redhat.com; robh@kernel.org; saeedm@nvidia.com; > wei.liu@kernel.org; Long Li <longli@microsoft.com>; boqun.feng@gmail.com; > Wei Hu <weh@microsoft.com> > Cc: linux-hyperv@vger.kernel.org; linux-kernel@vger.kernel.org; linux- > rdma@vger.kernel.org; netdev@vger.kernel.org > Subject: RE: [PATCH 4/6] Revert "PCI: hv: Fix a timing issue which causes > kdump to fail occasionally" > > > From: Dexuan Cui <decui@microsoft.com> > > Sent: Monday, March 27, 2023 9:51 PM > > To: bhelgaas@google.com; davem@davemloft.net; Dexuan Cui > > <decui@microsoft.com>; edumazet@google.com; Haiyang Zhang > > <haiyangz@microsoft.com>; Jake Oshins <jakeo@microsoft.com>; > > kuba@kernel.org; kw@linux.com; KY Srinivasan <kys@microsoft.com>; > > leon@kernel.org; linux-pci@vger.kernel.org; lpieralisi@kernel.org; > > Michael Kelley (LINUX) <mikelley@microsoft.com>; pabeni@redhat.com; > > robh@kernel.org; saeedm@nvidia.com; wei.liu@kernel.org; Long Li > > <longli@microsoft.com>; boqun.feng@gmail.com > > Cc: linux-hyperv@vger.kernel.org; linux-kernel@vger.kernel.org; > > linux-rdma@vger.kernel.org; netdev@vger.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@microsoft.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 Looks good to me. Thanks for fixing this. Wei
> -----Original Message----- > From: Dexuan Cui <decui@microsoft.com> > Sent: Tuesday, March 28, 2023 2:33 PM > To: bhelgaas@google.com; davem@davemloft.net; edumazet@google.com; > Haiyang Zhang <haiyangz@microsoft.com>; Jake Oshins > <jakeo@microsoft.com>; kuba@kernel.org; kw@linux.com; KY Srinivasan > <kys@microsoft.com>; leon@kernel.org; linux-pci@vger.kernel.org; > lpieralisi@kernel.org; Michael Kelley (LINUX) <mikelley@microsoft.com>; > pabeni@redhat.com; robh@kernel.org; saeedm@nvidia.com; > wei.liu@kernel.org; Long Li <longli@microsoft.com>; boqun.feng@gmail.com; > Wei Hu <weh@microsoft.com> > Cc: linux-hyperv@vger.kernel.org; linux-kernel@vger.kernel.org; linux- > rdma@vger.kernel.org; netdev@vger.kernel.org > Subject: RE: [PATCH 4/6] Revert "PCI: hv: Fix a timing issue which causes > kdump to fail occasionally" > > > From: Dexuan Cui <decui@microsoft.com> > > Sent: Monday, March 27, 2023 9:51 PM > > To: bhelgaas@google.com; davem@davemloft.net; Dexuan Cui > > <decui@microsoft.com>; edumazet@google.com; Haiyang Zhang > > <haiyangz@microsoft.com>; Jake Oshins <jakeo@microsoft.com>; > > kuba@kernel.org; kw@linux.com; KY Srinivasan <kys@microsoft.com>; > > leon@kernel.org; linux-pci@vger.kernel.org; lpieralisi@kernel.org; > > Michael Kelley (LINUX) <mikelley@microsoft.com>; pabeni@redhat.com; > > robh@kernel.org; saeedm@nvidia.com; wei.liu@kernel.org; Long Li > > <longli@microsoft.com>; boqun.feng@gmail.com > > Cc: linux-hyperv@vger.kernel.org; linux-kernel@vger.kernel.org; > > linux-rdma@vger.kernel.org; netdev@vger.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@microsoft.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 > Acked-by: Wei Hu <weh@microsoft.com>
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;
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@microsoft.com> --- drivers/pci/controller/pci-hyperv.c | 71 ++++++++++++++--------------- 1 file changed, 34 insertions(+), 37 deletions(-)