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From:   Dexuan Cui <decui@microsoft.com>
To:     Wei Hu <weh@microsoft.com>, KY Srinivasan <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        "wei.liu@kernel.org" <wei.liu@kernel.org>,
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        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Michael Kelley <mikelley@microsoft.com>
Subject: RE: [PATCH] PCI: pci-hyperv: Retry PCI bus D0 entry when the first
 attempt failed with invalid device state 0xC0000184.
Thread-Topic: [PATCH] PCI: pci-hyperv: Retry PCI bus D0 entry when the first
 attempt failed with invalid device state 0xC0000184.
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Date:   Mon, 27 Apr 2020 01:30:45 +0000
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> From: Wei Hu <weh@microsoft.com>
> Sent: Sunday, April 26, 2020 6:25 AM
> Subject: [PATCH] PCI: pci-hyperv: Retry PCI bus D0 entry when the first a=
ttempt
> failed with invalid device state 0xC0000184.

The title looks too long. :-)
Ideally it should be shorter than 75 chars. I suggest the part=20
"with invalid device state 0xC0000184. " should be removed.

> +#define STATUS_INVALID_DEVICE_STATE		0xC0000184
> +
> +static int hv_pci_bus_exit(struct hv_device *hdev, bool hibernating);

Should we change the name of the parameter 'hibernating'?

>  /**
>   * hv_pci_enter_d0() - Bring the "bus" into the D0 power state
>   * @hdev:	VMBus's tracking struct for this root PCI bus
> @@ -2748,8 +2752,10 @@ 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 =3D true;
>  	int ret;
>=20
> +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
> @@ -2780,6 +2786,30 @@ static int hv_pci_enter_d0(struct hv_device *hdev)
>  		dev_err(&hdev->device,
>  			"PCI Pass-through VSP failed D0 Entry with status %x\n",
>  			comp_pkt.completion_status);
> +
> +		/*
> +		 * 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 STATUS_INVALID_DEVICE_STATE.
> +		 * We need to explicitly request host to release the resource
> +		 * and try to enter D0 again.
> +		 */
> +		if (comp_pkt.completion_status =3D=3D STATUS_INVALID_DEVICE_STATE
> &&
> +		    retry) {

Maybe it's better to just retry for any error in comp_pkt.completion_status=
?
Just in case the host returns a slightly different error code in future.

Thanks,
-- Dexuan