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

[Suzuki K Poulose <Suzuki.Poulose@arm.com>]

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@redhat.com>
>> Cc: Jason Wang <jasowang@redhat.com>
>> Cc: Marc Zyngier <marc.zyngier@arm.com>
>> Cc: Christoffer Dall <cdall@linaro.org>
>> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> 
> 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