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Re: [Qemu-devel] [PATCH v2 2/5] virtio-blk: add "discard-wzeroes" boolea
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH v2 2/5] virtio-blk: add "discard-wzeroes" boolean property |
Date: |
Fri, 1 Feb 2019 10:16:50 -0500 |
On Thu, Jan 31, 2019 at 04:19:11PM +0100, Stefano Garzarella wrote:
> In order to avoid migration issues, we enable DISCARD and
> WRITE ZEROES features only for machine type >= 4.0
>
> Suggested-by: Dr. David Alan Gilbert <address@hidden>
> Signed-off-by: Stefano Garzarella <address@hidden>
> ---
> hw/block/virtio-blk.c | 2 ++
> hw/core/machine.c | 1 +
> include/hw/virtio/virtio-blk.h | 1 +
> 3 files changed, 4 insertions(+)
>
> diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
> index 8a6754d9a2..542ec52536 100644
> --- a/hw/block/virtio-blk.c
> +++ b/hw/block/virtio-blk.c
> @@ -1026,6 +1026,8 @@ static Property virtio_blk_properties[] = {
> DEFINE_PROP_UINT16("queue-size", VirtIOBlock, conf.queue_size, 128),
> DEFINE_PROP_LINK("iothread", VirtIOBlock, conf.iothread, TYPE_IOTHREAD,
> IOThread *),
> + DEFINE_PROP_BIT("discard-wzeroes", VirtIOBlock, conf.discard_wzeroes, 0,
> + true),
> DEFINE_PROP_END_OF_LIST(),
> };
>
Thinking about it, are there security implications for discard?
Should we make it default false?
> diff --git a/hw/core/machine.c b/hw/core/machine.c
> index 2629515363..ce98857af0 100644
> --- a/hw/core/machine.c
> +++ b/hw/core/machine.c
> @@ -30,6 +30,7 @@ GlobalProperty hw_compat_3_1[] = {
> { "memory-backend-memfd", "x-use-canonical-path-for-ramblock-id", "true"
> },
> { "tpm-crb", "ppi", "false" },
> { "tpm-tis", "ppi", "false" },
> + { "virtio-blk-device", "discard-wzeroes", "false" },
> };
> const size_t hw_compat_3_1_len = G_N_ELEMENTS(hw_compat_3_1);
>
> diff --git a/include/hw/virtio/virtio-blk.h b/include/hw/virtio/virtio-blk.h
> index 5117431d96..c336afb4cd 100644
> --- a/include/hw/virtio/virtio-blk.h
> +++ b/include/hw/virtio/virtio-blk.h
> @@ -40,6 +40,7 @@ struct VirtIOBlkConf
> uint32_t request_merging;
> uint16_t num_queues;
> uint16_t queue_size;
> + uint32_t discard_wzeroes;
> };
>
> struct VirtIOBlockDataPlane;
> --
> 2.20.1
Re: [Qemu-devel] [PATCH v2 2/5] virtio-blk: add "discard-wzeroes" boolean property, Michael S. Tsirkin, 2019/02/05