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From: Auger Eric <eric.auger@redhat.com>
To: Peter Xu <peterx@redhat.com>
Cc: peter.maydell@linaro.org, kevin.tian@intel.com, mst@redhat.com,
	tn@semihalf.com, qemu-devel@nongnu.org,
	alex.williamson@redhat.com, qemu-arm@nongnu.org,
	jean-philippe@linaro.org, bharat.bhushan@nxp.com,
	eric.auger.pro@gmail.com
Subject: Re: [Qemu-devel] [PATCH for-4.2 v10 03/15] virtio-iommu: Add skeleton
Date: Fri, 30 Aug 2019 10:12:18 +0200
Message-ID: <016b4d8e-7d65-d9e6-880f-8533e4f7f4af@redhat.com> (raw)
In-Reply-To: <20190830012614.GK8729@xz-x1>

Hi Peter,
On 8/30/19 3:26 AM, Peter Xu wrote:
> On Thu, Aug 29, 2019 at 02:18:42PM +0200, Auger Eric wrote:
>> Hi Peter,
>>
>> First of all, please forgive me for the delay.
>> On 8/15/19 3:54 PM, Peter Xu wrote:
>>> On Tue, Jul 30, 2019 at 07:21:25PM +0200, Eric Auger wrote:
>>>> +static void virtio_iommu_handle_command(VirtIODevice *vdev, VirtQueue *vq)
>>>> +{
>>>> +    VirtIOIOMMU *s = VIRTIO_IOMMU(vdev);
>>>> +    struct virtio_iommu_req_head head;
>>>> +    struct virtio_iommu_req_tail tail;
>>>
>>> [1]
>>>
>>>> +    VirtQueueElement *elem;
>>>> +    unsigned int iov_cnt;
>>>> +    struct iovec *iov;
>>>> +    size_t sz;
>>>> +
>>>> +    for (;;) {
>>>> +        elem = virtqueue_pop(vq, sizeof(VirtQueueElement));
>>>> +        if (!elem) {
>>>> +            return;
>>>> +        }
>>>> +
>>>> +        if (iov_size(elem->in_sg, elem->in_num) < sizeof(tail) ||
>>>> +            iov_size(elem->out_sg, elem->out_num) < sizeof(head)) {
>>>> +            virtio_error(vdev, "virtio-iommu bad head/tail size");
>>>> +            virtqueue_detach_element(vq, elem, 0);
>>>> +            g_free(elem);
>>>> +            break;
>>>> +        }
>>>> +
>>>> +        iov_cnt = elem->out_num;
>>>> +        iov = g_memdup(elem->out_sg, sizeof(struct iovec) * elem->out_num);
>>>
>>> Could I ask why memdup is needed here?
>> Indeed I don't think it is needed and besides iov is not freed!
>>
>> I got inspired from hw/net/virtio-net.c. To be honest I don't get why
>> the g_memdup is needed there either. The out_sg gets duplicated and
>> commands work on the duplicated data and not in place.
> 
> Oh true, I found that it's because of calling of iov_discard_front().
> Please have a look at 771b6ed37e3.  Though it seems to me that
> virtio-iommu does not truncate iovs so it should not be needed.

thanks for the sha1. indeed virtio-iommu does not use iov_discard_front
so I shouldn't need it.
> 
>>>
>>>> +        sz = iov_to_buf(iov, iov_cnt, 0, &head, sizeof(head));
>>>> +        if (unlikely(sz != sizeof(head))) {
>>>> +            tail.status = VIRTIO_IOMMU_S_DEVERR;
>>>
>>> Do you need to zero the reserved bits to make sure it won't contain
>>> garbage?  Same question to below uses of tail.
>> yes. I initialized tail.
>>>
>>>> +            goto out;
>>>> +        }
>>>> +        qemu_mutex_lock(&s->mutex);
>>>> +        switch (head.type) {
>>>> +        case VIRTIO_IOMMU_T_ATTACH:
>>>> +            tail.status = virtio_iommu_handle_attach(s, iov, iov_cnt);
>>>> +            break;
>>>> +        case VIRTIO_IOMMU_T_DETACH:
>>>> +            tail.status = virtio_iommu_handle_detach(s, iov, iov_cnt);
>>>> +            break;
>>>> +        case VIRTIO_IOMMU_T_MAP:
>>>> +            tail.status = virtio_iommu_handle_map(s, iov, iov_cnt);
>>>> +            break;
>>>> +        case VIRTIO_IOMMU_T_UNMAP:
>>>> +            tail.status = virtio_iommu_handle_unmap(s, iov, iov_cnt);
>>>> +            break;
>>>> +        default:
>>>> +            tail.status = VIRTIO_IOMMU_S_UNSUPP;
>>>> +        }
>>>> +        qemu_mutex_unlock(&s->mutex);
>>>> +
>>>> +out:
>>>> +        sz = iov_from_buf(elem->in_sg, elem->in_num, 0,
>>>> +                          &tail, sizeof(tail));
>>>> +        assert(sz == sizeof(tail));
>>>> +
>>>> +        virtqueue_push(vq, elem, sizeof(tail));
>>>
>>> s/tail/head/ (though they are the same size)?
>> That's unclear to me. Similarly when checking against virtio-net.c, the
>> element is pushed back to the used ring and len is set to the size of
>> the status with:
>>
>> /*
>>  * Control virtqueue data structures
>>  *
>>  * The control virtqueue expects a header in the first sg entry
>>  * and an ack/status response in the last entry.  Data for the
>>  * command goes in between.
>>  */
> 
> I was referencing the balloon code when reading the patch, e.g.,
> virtio_balloon_handle_output().  Though after I read more carefully I
> see that other places are using it as you described.  Now I tend to
> agree with you, because virtqueue_push() who calls
> virtqueue_unmap_sg() used the len to unmap in_sg[] rather than
> out_sg[].  So please ignore my previous comment.

OK
> 
> (then I'm not sure whether the usage in the balloon code was correct
>  now...)
> 
>>>
>>>> +        virtio_notify(vdev, vq);
>>>> +        g_free(elem);
>>>> +    }
>>>> +}
>>>
>>> [...]
>>>
>>>> +static void virtio_iommu_set_features(VirtIODevice *vdev, uint64_t val)
>>>> +{
>>>> +    VirtIOIOMMU *dev = VIRTIO_IOMMU(vdev);
>>>> +
>>>> +    dev->acked_features = val;
>>>> +    trace_virtio_iommu_set_features(dev->acked_features);
>>>> +}
>>>> +
>>>> +static const VMStateDescription vmstate_virtio_iommu_device = {
>>>> +    .name = "virtio-iommu-device",
>>>> +    .unmigratable = 1,
>>>
>>> Curious, is there explicit reason to not support migration from the
>>> first version? :)
>> The state is made of red black trees, lists. For the former there is no
>> VMSTATE* ready. I am working on it but I think this should be handled
>> separately
> 
> Fair enough.  Would you mind to add a similar comment above
> unmigratable?
sure

Thanks!

Eric
> 
> Thanks,
> 


  reply index

Thread overview: 53+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-30 17:21 [Qemu-devel] [PATCH for-4.2 v10 00/15] VIRTIO-IOMMU device Eric Auger
2019-07-30 17:21 ` [Qemu-devel] [PATCH for-4.2 v10 01/15] update-linux-headers: Import virtio_iommu.h Eric Auger
2019-07-30 17:21 ` [Qemu-devel] [PATCH for-4.2 v10 02/15] linux-headers: update against 5.3-rc2 Eric Auger
2019-07-30 17:21 ` [Qemu-devel] [PATCH for-4.2 v10 03/15] virtio-iommu: Add skeleton Eric Auger
2019-08-15 13:54   ` Peter Xu
2019-08-29 12:18     ` Auger Eric
2019-08-30  1:26       ` Peter Xu
2019-08-30  8:12         ` Auger Eric [this message]
2019-07-30 17:21 ` [Qemu-devel] [PATCH for-4.2 v10 04/15] virtio-iommu: Decode the command payload Eric Auger
2019-07-30 17:21 ` [Qemu-devel] [PATCH for-4.2 v10 05/15] virtio-iommu: Add the iommu regions Eric Auger
2019-08-16  4:00   ` Peter Xu
2019-08-29 12:51     ` Auger Eric
2019-07-30 17:21 ` [Qemu-devel] [PATCH for-4.2 v10 06/15] virtio-iommu: Endpoint and domains structs and helpers Eric Auger
2019-08-16  4:17   ` Peter Xu
2019-07-30 17:21 ` [Qemu-devel] [PATCH for-4.2 v10 07/15] virtio-iommu: Implement attach/detach command Eric Auger
2019-08-16  4:27   ` Peter Xu
2019-08-29 14:24     ` Auger Eric
2019-07-30 17:21 ` [Qemu-devel] [PATCH for-4.2 v10 08/15] virtio-iommu: Implement map/unmap Eric Auger
2019-08-19  8:11   ` Peter Xu
2019-09-03 11:37     ` Auger Eric
2019-09-04  1:44       ` Peter Xu
2019-09-04  4:23         ` Tian, Kevin
2019-09-04  5:37           ` Peter Xu
2019-09-04  5:46             ` Tian, Kevin
2019-09-04  7:54               ` Auger Eric
2019-09-04  8:32                 ` Peter Xu
2019-07-30 17:21 ` [Qemu-devel] [PATCH for-4.2 v10 09/15] virtio-iommu: Implement translate Eric Auger
2019-08-19  8:24   ` Peter Xu
2019-09-03 11:45     ` Auger Eric
2019-09-04  1:58       ` Peter Xu
2019-07-30 17:21 ` [Qemu-devel] [PATCH for-4.2 v10 10/15] virtio-iommu: Implement probe request Eric Auger
2019-08-19 12:08   ` Peter Xu
2019-09-03 12:23     ` Auger Eric
2019-07-30 17:21 ` [Qemu-devel] [PATCH for-4.2 v10 11/15] virtio-iommu: Expose the IOAPIC MSI reserved region when relevant Eric Auger
2019-07-30 19:38   ` Michael S. Tsirkin
2019-07-30 23:20     ` Tian, Kevin
2019-07-31  9:05       ` Auger Eric
2019-07-31 19:25       ` Michael S. Tsirkin
2019-07-31 19:44         ` Auger Eric
2019-07-31 23:23           ` Tian, Kevin
2019-07-30 17:21 ` [Qemu-devel] [PATCH for-4.2 v10 12/15] virtio-iommu: Implement fault reporting Eric Auger
2019-07-30 17:21 ` [Qemu-devel] [PATCH for-4.2 v10 13/15] virtio_iommu: Handle reserved regions in translation process Eric Auger
2019-08-19 12:44   ` Peter Xu
2019-09-01  6:38   ` Michael S. Tsirkin
2019-07-30 17:21 ` [Qemu-devel] [PATCH for-4.2 v10 14/15] virtio-iommu-pci: Add virtio iommu pci support Eric Auger
2019-07-30 19:35   ` Michael S. Tsirkin
2019-08-01 12:15     ` Auger Eric
2019-08-01 13:06       ` Michael S. Tsirkin
2019-08-01 13:49         ` Auger Eric
2019-09-01  6:40           ` Michael S. Tsirkin
2019-09-04 14:19             ` Auger Eric
2019-09-04 21:36               ` Michael S. Tsirkin
2019-07-30 17:21 ` [Qemu-devel] [PATCH for-4.2 v10 15/15] hw/arm/virt: Add the virtio-iommu device tree mappings Eric Auger

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