DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com B62D58F4F9
Date: Thu, 17 Aug 2017 07:00:17 -0600
From: Alex Williamson <alex.williamson@redhat.com>
To: Jan Glauber <jglauber@cavium.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>, linux-pci@vger.kernel.org,
        linux-kernel@vger.kernel.org, david.daney@cavium.com,
        Jon Masters <jcm@redhat.com>,
        Robert Richter <robert.richter@cavium.com>,
        linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org
Subject: Re: [PATCH v2 3/3] vfio/pci: Don't probe devices that can't be
 reset
Message-ID: <20170817070017.1e9c9456@w520.home>
In-Reply-To: <1502957663-5527-4-git-send-email-jglauber@cavium.com>
References: <1502957663-5527-1-git-send-email-jglauber@cavium.com>
        <1502957663-5527-4-git-send-email-jglauber@cavium.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1457
Lines: 41

On Thu, 17 Aug 2017 10:14:23 +0200
Jan Glauber <jglauber@cavium.com> wrote:

> If a PCI device supports neither function-level reset, nor slot
> or bus reset then refuse to probe it. A line is printed to inform
> the user.

But that's not what this does, this requires that the device is on a
reset-able bus.  This is a massive regression.  With this we could no
longer assign devices on the root complex or any device which doesn't
return from bus reset and currently makes use of the NO_BUS_RESET flag
and works happily otherwise.  Full NAK.  Thanks,

Alex
 
> Without this change starting qemu with a vfio-pci device can lead to
> a kernel panic on some Cavium cn8xxx systems, depending on the used
> device.
> 
> Signed-off-by: Jan Glauber <jglauber@cavium.com>
> ---
>  drivers/vfio/pci/vfio_pci.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
> index 063c1ce..029ba13 100644
> --- a/drivers/vfio/pci/vfio_pci.c
> +++ b/drivers/vfio/pci/vfio_pci.c
> @@ -1196,6 +1196,12 @@ static int vfio_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>  	if (pdev->hdr_type != PCI_HEADER_TYPE_NORMAL)
>  		return -EINVAL;
>  
> +	ret = pci_probe_reset_bus(pdev->bus);
> +	if (ret) {
> +		dev_warn(&pdev->dev, "Refusing to probe because reset is not possible.\n");
> +		return ret;
> +	}
> +
>  	group = vfio_iommu_group_get(&pdev->dev);
>  	if (!group)
>  		return -EINVAL;