Re: [Qemu-devel] [PATCH v1 2/2] ide: support reporting of rotation rate

[Eric Blake <eblake@redhat.com>]

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On 10/04/2017 06:40 AM, Daniel P. Berrange wrote:
> The Linux kernel will query the ATA IDENTITY DEVICE data, word 217
> to determine the rotations per minute of the disk. If this has
> the value 1, it is taken to be an SSD and so Linux sets the
> 'rotational' flag to 0 for the I/O queue and will stop using that
> disk as a source of random entropy. Other operating systems may
> also take into account rotation rate when setting up default
> behaviour.
> 
> Mgmt apps should be able to set the rotation rate for virtualized
> block devices, based on characteristics of the host storage in use,
> so that the guest OS gets sensible behaviour out of the box. This
> patch thus adds a 'rotation-rate' parameter for 'ide-hd' device
> types.
> 
> Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
> ---
>  hw/ide/core.c             | 1 +

> +++ b/include/hw/ide/internal.h
> @@ -508,6 +508,14 @@ struct IDEDevice {
>      char *serial;
>      char *model;
>      uint64_t wwn;
> +    /*
> +     * 0x0000        - rotation rate not reported
> +     * 0x0001        - non-rotating medium (SSD)
> +     * 0x0002-0x0400 - reserved
> +     * 0x0401-0xffe  - rotations per minute

s/0xffe/0xfffe/

> +     * 0xffff        - reserved
> +     */
> +    uint16_t rotation_rate;
>  };
>  
>  /* These are used for the error_status field of IDEBus */
> 

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org


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