Re: [PATCH v1 01/16] virtio: Validate queue pfn for 32bit transports

[Suzuki K Poulose]

On 09/01/18 23:29, Michael S. Tsirkin wrote:
> On Tue, Jan 09, 2018 at 07:03:56PM +0000, Suzuki K Poulose wrote:
> > virtio-mmio using virtio-v1 and virtio legacy pci use a 32bit PFN
> > for the queue. If the queue pfn is too large to fit in 32bits, which
> > we could hit on arm64 systems with 52bit physical addresses (even with
> > 64K page size), we simply miss out a proper link to the other side of
> > the queue.
> >
> > Add a check to validate the PFN, rather than silently breaking
> > the devices.
> >
> > Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
> > Cc: Jason Wang <jasowang@xxxxxxxxxx>
> > Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
> > Cc: Christoffer Dall <cdall@xxxxxxxxxx>
> > Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
>
> Could you guys please work on virtio 1 support in
> for virtio mmio in qemu though?
> It's not a lot of code.

Did you mean kvmtool ? Qemu already supports virto-1.

> > ---
> >   drivers/virtio/virtio_mmio.c       | 19 ++++++++++++++++---
> >   drivers/virtio/virtio_pci_legacy.c | 11 +++++++++--
> >   2 files changed, 25 insertions(+), 5 deletions(-)
>
> I'd rather see this as 2 patches.

OK, I will split them.

> > diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
> > index a9192fe4f345..47109baf37f7 100644
> > --- a/drivers/virtio/virtio_mmio.c
> > +++ b/drivers/virtio/virtio_mmio.c
> > @@ -358,6 +358,7 @@ static struct virtqueue *vm_setup_vq(struct virtio_device *vdev, unsigned index,
> >   	struct virtqueue *vq;
> >   	unsigned long flags;
> >   	unsigned int num;
> > +	u64 addr;
> >   	int err;
> >   
> >   	if (!name)
> > @@ -394,16 +395,26 @@ static struct virtqueue *vm_setup_vq(struct virtio_device *vdev, unsigned index,
> >   		goto error_new_virtqueue;
> >   	}
> >   
> > +	addr = virtqueue_get_desc_addr(vq);
> > +	/*
> > +	 * virtio-mmio v1 uses a 32bit QUEUE PFN. If we have something that
> > +	 * doesn't fit in 32bit, fail the setup rather than pretending to
> > +	 * be successful.
> > +	 */
> > +	if (vm_dev->version == 1 && (addr >> (PAGE_SHIFT + 32))) {
> > +		dev_err(&vdev->dev, "virtio-mmio: queue address too large\n");
> > +		err = -ENOMEM;
> > +		goto error_bad_pfn;
> > +	}
> > +
>
> Can you please move this below to where it's actually used?

The reason for keeping it here was to skip selecting the Queue number if we
have a bad PFN. May be it doesn't make much difference as we write PFN = 0 anyway
down.

> >   	/* Activate the queue */
> >   	writel(virtqueue_get_vring_size(vq), vm_dev->base + VIRTIO_MMIO_QUEUE_NUM);
> >   	if (vm_dev->version == 1) {
> >   		writel(PAGE_SIZE, vm_dev->base + VIRTIO_MMIO_QUEUE_ALIGN);
> > -		writel(virtqueue_get_desc_addr(vq) >> PAGE_SHIFT,
> > +		writel(addr >> PAGE_SHIFT,
> >   				vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);
> >   	} else {
> > -		u64 addr;
> >   
> > -		addr = virtqueue_get_desc_addr(vq);
> >   		writel((u32)addr, vm_dev->base + VIRTIO_MMIO_QUEUE_DESC_LOW);
> >   		writel((u32)(addr >> 32),
> >   				vm_dev->base + VIRTIO_MMIO_QUEUE_DESC_HIGH);
> > @@ -430,6 +441,8 @@ static struct virtqueue *vm_setup_vq(struct virtio_device *vdev, unsigned index,
> >   
> >   	return vq;
> >   
> > +error_bad_pfn:
> > +	vring_del_virtqueue(vq);
> >   error_new_virtqueue:
> >   	if (vm_dev->version == 1) {
> >   		writel(0, vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);
> > diff --git a/drivers/virtio/virtio_pci_legacy.c b/drivers/virtio/virtio_pci_legacy.c
> > index 2780886e8ba3..099d2cfb47b3 100644
> > --- a/drivers/virtio/virtio_pci_legacy.c
> > +++ b/drivers/virtio/virtio_pci_legacy.c
> > @@ -122,6 +122,7 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
> >   	struct virtqueue *vq;
> >   	u16 num;
> >   	int err;
> > +	u64 q_pfn;
> >   
> >   	/* Select the queue we're interested in */
> >   	iowrite16(index, vp_dev->ioaddr + VIRTIO_PCI_QUEUE_SEL);
> > @@ -141,9 +142,15 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
> >   	if (!vq)
> >   		return ERR_PTR(-ENOMEM);
> >   
> > +	q_pfn = virtqueue_get_desc_addr(vq) >> VIRTIO_PCI_QUEUE_ADDR_SHIFT;
> > +	if (q_pfn >> 32) {
> > +		dev_err(&vp_dev->pci_dev->dev, "virtio-pci queue PFN too large\n");
> > +		err = -ENOMEM;
> > +		goto out_deactivate;
>
> You never set up the address, it's cleaner to add another target
> and not reset it.

Thats right. However, the only thing we do is writing PFN=0, which would be a good
thing to do to indicate the error to the host ? I could skip it if you think it is
not needed.


Thanks
Suzuki