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Re: [Qemu-devel] [PATCH v1 2/2] ide: support reporting of rotation rate
From: |
John Snow |
Subject: |
Re: [Qemu-devel] [PATCH v1 2/2] ide: support reporting of rotation rate |
Date: |
Wed, 4 Oct 2017 11:57:58 -0400 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 |
On 10/04/2017 07:40 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 <address@hidden>
> ---
> hw/ide/core.c | 1 +
> hw/ide/qdev.c | 1 +
> include/hw/ide/internal.h | 8 ++++++++
> 3 files changed, 10 insertions(+)
>
> diff --git a/hw/ide/core.c b/hw/ide/core.c
> index 5f1cd3b91f..a04766aee7 100644
> --- a/hw/ide/core.c
> +++ b/hw/ide/core.c
> @@ -208,6 +208,7 @@ static void ide_identify(IDEState *s)
> if (dev && dev->conf.discard_granularity) {
> put_le16(p + 169, 1); /* TRIM support */
> }
> + put_le16(p + 217, dev->rotation_rate); /* Nominal media rotation rate */
>
> ide_identify_size(s);
> s->identify_set = 1;
> diff --git a/hw/ide/qdev.c b/hw/ide/qdev.c
> index d60ac25be0..a5181b4448 100644
> --- a/hw/ide/qdev.c
> +++ b/hw/ide/qdev.c
> @@ -299,6 +299,7 @@ static Property ide_hd_properties[] = {
> DEFINE_BLOCK_CHS_PROPERTIES(IDEDrive, dev.conf),
> DEFINE_PROP_BIOS_CHS_TRANS("bios-chs-trans",
> IDEDrive, dev.chs_trans, BIOS_ATA_TRANSLATION_AUTO),
> + DEFINE_PROP_UINT16("rotation_rate", IDEDrive, dev.rotation_rate, 0),
> DEFINE_PROP_END_OF_LIST(),
> };
>
> diff --git a/include/hw/ide/internal.h b/include/hw/ide/internal.h
> index e641012b48..31851b44d1 100644
> --- a/include/hw/ide/internal.h
> +++ 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
> + * 0xffff - reserved
> + */
> + uint16_t rotation_rate;
> };
>
> /* These are used for the error_status field of IDEBus */
>
With Eric's comment addressed:
Reviewed-by: John Snow <address@hidden>
It'd be nice if we could have a magic autodetect value, but this is a
strict improvement anyway.
(Actually, probably most of the identify data needs to be audited, but
the perceived cost:benefit ratio doesn't look too favorable.)