ide: support reporting of rotation rate

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>
Message-Id: <20171004114008.14849-3-berrange@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/hw/ide/core.c b/hw/ide/core.c
index 5f1cd3b91f313b8f3c7b25967741641b32210f10..a04766aee7172dfdcf62e6e70febb24d557d6fcf 100644 (file)
--- 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 d60ac25be0ed98e7dd1814e61b92ec89eb290390..a5181b444899940684444b9702c208b15433358e 100644 (file)
--- 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 e641012b48e26ade7f9059d6c1411a282fe038b5..31851b44d1b8da2b31971b76a4a1f9bcc62494ca 100644 (file)
--- 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 */