Re: [PATCH v2 02/10] virtio-mem: Factor out traversing unplugged ranges

[Pankaj Gupta]

> Let's factor out the core logic, to be reused soon.
>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: "Michael S. Tsirkin" <mst@redhat.com>
> Cc: Alex Williamson <alex.williamson@redhat.com>
> Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
> Cc: Igor Mammedov <imammedo@redhat.com>
> Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
> Cc: Peter Xu <peterx@redhat.com>
> Cc: Auger Eric <eric.auger@redhat.com>
> Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
> Cc: teawater <teawaterz@linux.alibaba.com>
> Cc: Marek Kedzierski <mkedzier@redhat.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>  hw/virtio/virtio-mem.c | 86 ++++++++++++++++++++++++------------------
>  1 file changed, 49 insertions(+), 37 deletions(-)
>
> diff --git a/hw/virtio/virtio-mem.c b/hw/virtio/virtio-mem.c
> index 655824ff81..471e464171 100644
> --- a/hw/virtio/virtio-mem.c
> +++ b/hw/virtio/virtio-mem.c
> @@ -145,6 +145,33 @@ static bool virtio_mem_is_busy(void)
>      return migration_in_incoming_postcopy() || !migration_is_idle();
>  }
>
> +typedef int (*virtio_mem_range_cb)(const VirtIOMEM *vmem, void *arg,
> +                                   uint64_t offset, uint64_t size);
> +
> +static int virtio_mem_for_each_unplugged_range(const VirtIOMEM *vmem, void 
> *arg,
> +                                               virtio_mem_range_cb cb)
> +{
> +    unsigned long first_zero_bit, last_zero_bit;
> +    uint64_t offset, size;
> +    int ret = 0;
> +
> +    first_zero_bit = find_first_zero_bit(vmem->bitmap, vmem->bitmap_size);
> +    while (first_zero_bit < vmem->bitmap_size) {
> +        offset = first_zero_bit * vmem->block_size;
> +        last_zero_bit = find_next_bit(vmem->bitmap, vmem->bitmap_size,
> +                                      first_zero_bit + 1) - 1;
> +        size = (last_zero_bit - first_zero_bit + 1) * vmem->block_size;
> +
> +        ret = cb(vmem, arg, offset, size);
> +        if (ret) {
> +            break;
> +        }
> +        first_zero_bit = find_next_zero_bit(vmem->bitmap, vmem->bitmap_size,
> +                                            last_zero_bit + 2);
> +    }
> +    return ret;
> +}
> +
>  static bool virtio_mem_test_bitmap(VirtIOMEM *vmem, uint64_t start_gpa,
>                                     uint64_t size, bool plugged)
>  {
> @@ -594,33 +621,27 @@ static void virtio_mem_device_unrealize(DeviceState 
> *dev)
>      ram_block_discard_require(false);
>  }
>
> -static int virtio_mem_restore_unplugged(VirtIOMEM *vmem)
> +static int virtio_mem_discard_range_cb(const VirtIOMEM *vmem, void *arg,
> +                                       uint64_t offset, uint64_t size)
>  {
>      RAMBlock *rb = vmem->memdev->mr.ram_block;
> -    unsigned long first_zero_bit, last_zero_bit;
> -    uint64_t offset, length;
>      int ret;
>
> -    /* Find consecutive unplugged blocks and discard the consecutive range. 
> */
> -    first_zero_bit = find_first_zero_bit(vmem->bitmap, vmem->bitmap_size);
> -    while (first_zero_bit < vmem->bitmap_size) {
> -        offset = first_zero_bit * vmem->block_size;
> -        last_zero_bit = find_next_bit(vmem->bitmap, vmem->bitmap_size,
> -                                      first_zero_bit + 1) - 1;
> -        length = (last_zero_bit - first_zero_bit + 1) * vmem->block_size;
> -
> -        ret = ram_block_discard_range(rb, offset, length);
> -        if (ret) {
> -            error_report("Unexpected error discarding RAM: %s",
> -                         strerror(-ret));
> -            return -EINVAL;
> -        }
> -        first_zero_bit = find_next_zero_bit(vmem->bitmap, vmem->bitmap_size,
> -                                            last_zero_bit + 2);
> +    ret = ram_block_discard_range(rb, offset, size);
> +    if (ret) {
> +        error_report("Unexpected error discarding RAM: %s", strerror(-ret));
> +        return -EINVAL;
>      }
>      return 0;
>  }
>
> +static int virtio_mem_restore_unplugged(VirtIOMEM *vmem)
> +{
> +    /* Make sure all memory is really discarded after migration. */
> +    return virtio_mem_for_each_unplugged_range(vmem, NULL,
> +                                               virtio_mem_discard_range_cb);
> +}
> +
>  static int virtio_mem_post_load(void *opaque, int version_id)
>  {
>      if (migration_in_incoming_postcopy()) {
> @@ -872,28 +893,19 @@ static void virtio_mem_set_block_size(Object *obj, 
> Visitor *v, const char *name,
>      vmem->block_size = value;
>  }
>
> -static void virtio_mem_precopy_exclude_unplugged(VirtIOMEM *vmem)
> +static int virtio_mem_precopy_exclude_range_cb(const VirtIOMEM *vmem, void 
> *arg,
> +                                               uint64_t offset, uint64_t 
> size)
>  {
>      void * const host = qemu_ram_get_host_addr(vmem->memdev->mr.ram_block);
> -    unsigned long first_zero_bit, last_zero_bit;
> -    uint64_t offset, length;
>
> -    /*
> -     * Find consecutive unplugged blocks and exclude them from migration.
> -     *
> -     * Note: Blocks cannot get (un)plugged during precopy, no locking needed.
> -     */
> -    first_zero_bit = find_first_zero_bit(vmem->bitmap, vmem->bitmap_size);
> -    while (first_zero_bit < vmem->bitmap_size) {
> -        offset = first_zero_bit * vmem->block_size;
> -        last_zero_bit = find_next_bit(vmem->bitmap, vmem->bitmap_size,
> -                                      first_zero_bit + 1) - 1;
> -        length = (last_zero_bit - first_zero_bit + 1) * vmem->block_size;
> +    qemu_guest_free_page_hint(host + offset, size);
> +    return 0;
> +}
>
> -        qemu_guest_free_page_hint(host + offset, length);
> -        first_zero_bit = find_next_zero_bit(vmem->bitmap, vmem->bitmap_size,
> -                                            last_zero_bit + 2);
> -    }
> +static void virtio_mem_precopy_exclude_unplugged(VirtIOMEM *vmem)
> +{
> +    virtio_mem_for_each_unplugged_range(vmem, NULL,
> +                                        virtio_mem_precopy_exclude_range_cb);
>  }
>
>  static int virtio_mem_precopy_notify(NotifierWithReturn *n, void *data)

Reviewed-by: Pankaj Gupta <pankaj.gupta@cloud.ionos.com>