Re: [PATCH v1 10/17] virtio-mem: Paravirtualized memory hot(un)plug

David Hildenbrand
2020-05-15T16:49:07Z

On 15.05.20 17:37, Dr. David Alan Gilbert wrote:
> I'm not sure if it's possible to split this up; it's a bit big.

Functionality-wise, it's the bare minimum. I could split out handling of
all 4 request types, but they are only ~150-200 LOC. Not sure if that is
really worth the trouble. open for suggestions.

> It could also do with a pile of trace_ entries to figure out what it's
> doing.

Good idea, will add that with a patch on top.

[...]

>> +static int virtio_mem_set_block_state(VirtIOMEM *vmem, uint64_t start_gpa,
>> + uint64_t size, bool plug)
>> +{
>> + const uint64_t offset = start_gpa - vmem->addr;
>> + int ret;
>> +
>> + if (!plug) {
>> + if (virtio_mem_discard_inhibited()) {
>> + return -EBUSY;
>> + }
>> + /* Note: Discarding should never fail at this point. */
>> + ret = ram_block_discard_range(vmem->memdev->mr.ram_block, offset, size);
>> + if (ret) {
>
> error_report ?

error_report("Unexpected error discarding RAM: %s",
strerror(-ret));
it is.

[...]

>> + ret = ram_block_discard_range(rb, 0, qemu_ram_get_used_length(rb));
>> + if (ret) {
>> + /* Note: Discarding should never fail at this point. */
>
> error_report?

dito

>
>> + return -EBUSY;
>> + }
>> + bitmap_clear(vmem->bitmap, 0, vmem->bitmap_size);
>> + vmem->size = 0;
>> +
>> + virtio_mem_resize_usable_region(vmem, vmem->requested_size, true);
>> + return 0;
>> +}

[...]

>> +static void virtio_mem_handle_request(VirtIODevice *vdev, VirtQueue *vq)
>> +{
>> + const int len = sizeof(struct virtio_mem_req);
>> + VirtIOMEM *vmem = VIRTIO_MEM(vdev);
>> + VirtQueueElement *elem;
>> + struct virtio_mem_req req;
>> + uint64_t type;
>> +
>> + while (true) {
>> + elem = virtqueue_pop(vq, sizeof(VirtQueueElement));
>> + if (!elem) {
>> + return;
>> + }
>> +
>> + if (iov_to_buf(elem->out_sg, elem->out_num, 0, &req, len) < len) {
>> + virtio_mem_bad_request(vmem, "invalid request size");
>
> Print the size.

Make sense, I'll probably get rid of virtio_mem_bad_request() and just
do the virtio_error() directly with additional paramaters.

>
>> + g_free(elem);
>> + return;
>> + }
>> +
>> + if (iov_size(elem->in_sg, elem->in_num) <
>> + sizeof(struct virtio_mem_resp)) {
>> + virtio_mem_bad_request(vmem, "not enough space for response");
>> + g_free(elem);
>> + return;
>> + }
>> +
>> + type = le16_to_cpu(req.type);
>> + switch (type) {
>> + case VIRTIO_MEM_REQ_PLUG:
>> + virtio_mem_plug_request(vmem, elem, &req);
>> + break;
>> + case VIRTIO_MEM_REQ_UNPLUG:
>> + virtio_mem_unplug_request(vmem, elem, &req);
>> + break;
>> + case VIRTIO_MEM_REQ_UNPLUG_ALL:
>> + virtio_mem_unplug_all_request(vmem, elem);
>> + break;
>> + case VIRTIO_MEM_REQ_STATE:
>> + virtio_mem_state_request(vmem, elem, &req);
>> + break;
>> + default:
>> + virtio_mem_bad_request(vmem, "unknown request type");
>
> Could include the type .

Yes, will do!

[...]

>> +
>> +static int virtio_mem_pre_save(void *opaque)
>> +{
>> + VirtIOMEM *vmem = VIRTIO_MEM(opaque);
>> +
>> + vmem->migration_addr = vmem->addr;
>> + vmem->migration_block_size = vmem->block_size;
>
> You might look at VMSTATE_WITH_TMP could avoid you having the dummy
> fields.

Thanks, will have a look.

--
Thanks,

David / dhildenb