linux-kernel - RE: [PATCH v3 1/2] PCI: hv: Fix the PCI HyperV probe failure path to release resource properly

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Message-ID: <MW2PR2101MB1052E75BB228D7AF499B6135D7A50@MW2PR2101MB1052.namprd21.prod.outlook.com>
Date:   Thu, 7 May 2020 14:29:36 +0000
From:   Michael Kelley <mikelley@...rosoft.com>
To:     Wei Hu <weh@...rosoft.com>, KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        "lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
        "robh@...nel.org" <robh@...nel.org>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Dexuan Cui <decui@...rosoft.com>
Subject: RE: [PATCH v3 1/2] PCI: hv: Fix the PCI HyperV probe failure path to
 release resource properly

From: Wei Hu <weh@...rosoft.com> Sent: Wednesday, May 6, 2020 10:02 PM
> 
> In some error cases in hv_pci_probe(), allocated resources are not freed.
> Fix this by adding a field to keep track of the high water mark for slots
> that have resources allocated to them.  In case of an error, this high
> water mark is used to know which slots have resources that must be released.
> Since slots are numbered starting with zero, a value of -1 indicates no
> slots have been allocated resources.  There may be unused slots in the range
> between slot 0 and the high water mark slot, but these slots are already
> ignored by the existing code in the allocate and release loops with the call
> to get_pcichild_wslot().
> 
> Signed-off-by: Wei Hu <weh@...rosoft.com>
> ---
>     v3: Add detailed explanation of this patch in commit log per Lorenzo
>     Pieralisi's suggestions.
> 
>  drivers/pci/controller/pci-hyperv.c | 20 ++++++++++++++++----
>  1 file changed, 16 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
> index e15022ff63e3..e6fac0187722 100644
> --- a/drivers/pci/controller/pci-hyperv.c
> +++ b/drivers/pci/controller/pci-hyperv.c
> @@ -480,6 +480,9 @@ struct hv_pcibus_device {
> 
>  	struct workqueue_struct *wq;
> 
> +	/* Highest slot of child device with resources allocated */
> +	int wslot_res_allocated;
> +
>  	/* hypercall arg, must not cross page boundary */
>  	struct hv_retarget_device_interrupt retarget_msi_interrupt_params;
> 
> @@ -2847,7 +2850,7 @@ static int hv_send_resources_allocated(struct hv_device *hdev)
>  	struct hv_pci_dev *hpdev;
>  	struct pci_packet *pkt;
>  	size_t size_res;
> -	u32 wslot;
> +	int wslot;
>  	int ret;
> 
>  	size_res = (hbus->protocol_version < PCI_PROTOCOL_VERSION_1_2)
> @@ -2900,6 +2903,8 @@ static int hv_send_resources_allocated(struct hv_device *hdev)
>  				comp_pkt.completion_status);
>  			break;
>  		}
> +
> +		hbus->wslot_res_allocated = wslot;
>  	}
> 
>  	kfree(pkt);
> @@ -2918,10 +2923,10 @@ static int hv_send_resources_released(struct hv_device *hdev)
>  	struct hv_pcibus_device *hbus = hv_get_drvdata(hdev);
>  	struct pci_child_message pkt;
>  	struct hv_pci_dev *hpdev;
> -	u32 wslot;
> +	int wslot;
>  	int ret;
> 
> -	for (wslot = 0; wslot < 256; wslot++) {
> +	for (wslot = hbus->wslot_res_allocated; wslot >= 0; wslot--) {
>  		hpdev = get_pcichild_wslot(hbus, wslot);
>  		if (!hpdev)
>  			continue;
> @@ -2936,8 +2941,12 @@ static int hv_send_resources_released(struct hv_device *hdev)
>  				       VM_PKT_DATA_INBAND, 0);
>  		if (ret)
>  			return ret;
> +
> +		hbus->wslot_res_allocated = wslot - 1;
>  	}
> 
> +	hbus->wslot_res_allocated = -1;
> +
>  	return 0;
>  }
> 
> @@ -3037,6 +3046,7 @@ static int hv_pci_probe(struct hv_device *hdev,
>  	if (!hbus)
>  		return -ENOMEM;
>  	hbus->state = hv_pcibus_init;
> +	hbus->wslot_res_allocated = -1;
> 
>  	/*
>  	 * The PCI bus "domain" is what is called "segment" in ACPI and other
> @@ -3136,7 +3146,7 @@ static int hv_pci_probe(struct hv_device *hdev,
> 
>  	ret = hv_pci_allocate_bridge_windows(hbus);
>  	if (ret)
> -		goto free_irq_domain;
> +		goto exit_d0;
> 
>  	ret = hv_send_resources_allocated(hdev);
>  	if (ret)
> @@ -3154,6 +3164,8 @@ static int hv_pci_probe(struct hv_device *hdev,
> 
>  free_windows:
>  	hv_pci_free_bridge_windows(hbus);
> +exit_d0:
> +	(void) hv_pci_bus_exit(hdev, true);
>  free_irq_domain:
>  	irq_domain_remove(hbus->irq_domain);
>  free_fwnode:
> --
> 2.20.1

Reviewed-by: Michael Kelley <mikelley@...rosoft.com>