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 <berra...@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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