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Re: [Qemu-devel] [RFC v1] block/NVMe: introduce a new vhost NVMe host de
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [RFC v1] block/NVMe: introduce a new vhost NVMe host device to QEMU |
Date: |
Wed, 17 Jan 2018 08:10:50 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.0 |
On 17/01/2018 01:53, Liu, Changpeng wrote:
>> Second, virtio-based vhost-user remains QEMU's preferred method for
>> high-performance I/O in guests. Discard support is missing and that is
>> important for SSDs; that should be fixed in the virtio spec. Are there
> Previously I have a patch adding DISCARD support to virtio-blk, but I didn't
> find
> the way using svn to update the spec patch, any git repository I can use
> to update the virtio-blk spec ? I think I can pick up the feature again.
There is https://github.com/oasis-tcs/virtio-spec.
You should add support for all of:
1) a command that can do WRITE ZERO, WRITE ZERO with discard, and
advisory DISCARD of a range of blocks. The command must be controlled
by a new feature bit.
2) a configuration space element for discard granularity, controlled by
the same feature bit as (1)
3) a feature bit that is 1 if WRITE ZERO with discard can actually
discard parts that are aligned to the granularity
Thanks,
Paolo