Upstream QEMU supports it since commit fb0490f69.
---
docs/formatdomain.html.in | 9 +++++++++
docs/schemas/domaincommon.rng | 11 +++++++++++
src/conf/domain_conf.c | 24 +++++++++++++++++++++++-
src/conf/domain_conf.h | 10 ++++++++++
src/libvirt_private.syms | 2 ++
src/qemu/qemu_capabilities.c | 3 +++
src/qemu/qemu_capabilities.h | 1 +
src/qemu/qemu_command.c | 11 +++++++++++
8 files changed, 70 insertions(+), 1 deletions(-)
diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
index 9cf0f12..779317f 100644
--- a/docs/formatdomain.html.in
+++ b/docs/formatdomain.html.in
@@ -1187,6 +1187,15 @@
<b>In general you should leave this option alone, unless you
are very certain you know what you are doing.</b>
</li>
+ <li>
+ The optional <code>copy_on_read</code> attribute controls
+ wether to copy read backing file into the image file. The
+ value can be either "on" or "off".
+ Copy-on-read avoids accessing the same backing file sectors
+ repeatedly and is useful when the backing file is over a slow
+ network. By default copy-on-read is off.
+ <span class='since'>Since 0.9.9 (QEMU and KVM only)</span>
+ </li>
</ul>
</dd>
<dt><code>boot</code></dt>
diff --git a/docs/schemas/domaincommon.rng b/docs/schemas/domaincommon.rng
index 553a6f0..b511ec2 100644
--- a/docs/schemas/domaincommon.rng
+++ b/docs/schemas/domaincommon.rng
@@ -959,6 +959,14 @@
</choice>
</attribute>
</define>
+ <define name="copy_on_read">
+ <attribute name='copy_on_read'>
+ <choice>
+ <value>on</value>
+ <value>off</value>
+ </choice>
+ </attribute>
+ </define>
<define name="controller">
<element name="controller">
<choice>
@@ -1308,6 +1316,9 @@
<optional>
<ref name="event_idx"/>
</optional>
+ <optional>
+ <ref name="copy_on_read"/>
+ </optional>
<empty/>
</element>
</optional>
diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 2897b4a..a51eb40 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -208,6 +208,11 @@ VIR_ENUM_IMPL(virDomainVirtioEventIdx, VIR_DOMAIN_VIRTIO_EVENT_IDX_LAST,
"on",
"off")
+VIR_ENUM_IMPL(virDomainDiskCopyOnRead, VIR_DOMAIN_DISK_COPY_ON_READ_LAST,
+ "default",
+ "on",
+ "off")
+
VIR_ENUM_IMPL(virDomainDiskSnapshot, VIR_DOMAIN_DISK_SNAPSHOT_LAST,
"default",
"no",
@@ -2621,6 +2626,7 @@ virDomainDiskDefParseXML(virCapsPtr caps,
char *iotag = NULL;
char *ioeventfd = NULL;
char *event_idx = NULL;
+ char *copy_on_read = NULL;
char *devaddr = NULL;
virStorageEncryptionPtr encryption = NULL;
char *serial = NULL;
@@ -2749,6 +2755,7 @@ virDomainDiskDefParseXML(virCapsPtr caps,
iotag = virXMLPropString(cur, "io");
ioeventfd = virXMLPropString(cur, "ioeventfd");
event_idx = virXMLPropString(cur, "event_idx");
+ copy_on_read = virXMLPropString(cur, "copy_on_read");
} else if (xmlStrEqual(cur->name, BAD_CAST "auth")) {
authUsername = virXMLPropString(cur, "username");
if (authUsername == NULL) {
@@ -3053,6 +3060,17 @@ virDomainDiskDefParseXML(virCapsPtr caps,
def->event_idx = idx;
}
+ if (copy_on_read) {
+ int cor;
+ if ((cor = virDomainDiskCopyOnReadTypeFromString(copy_on_read)) <= 0) {
+ virDomainReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+ _("unknown disk copy_on_read mode '%s'"),
+ copy_on_read);
+ goto error;
+ }
+ def->copy_on_read = cor;
+ }
+
if (devaddr) {
if (virDomainParseLegacyDeviceAddress(devaddr,
&def->info.addr.pci) < 0) {
@@ -3146,6 +3164,7 @@ cleanup:
VIR_FREE(iotag);
VIR_FREE(ioeventfd);
VIR_FREE(event_idx);
+ VIR_FREE(copy_on_read);
VIR_FREE(devaddr);
VIR_FREE(serial);
virStorageEncryptionFree(encryption);
@@ -9768,6 +9787,7 @@ virDomainDiskDefFormat(virBufferPtr buf,
const char *iomode = virDomainDiskIoTypeToString(def->iomode);
const char *ioeventfd = virDomainIoEventFdTypeToString(def->ioeventfd);
const char *event_idx = virDomainVirtioEventIdxTypeToString(def->event_idx);
+ const char *copy_on_read = virDomainVirtioEventIdxTypeToString(def->copy_on_read);
const char *startupPolicy = virDomainStartupPolicyTypeToString(def->startupPolicy);
char uuidstr[VIR_UUID_STRING_BUFLEN];
@@ -9808,7 +9828,7 @@ virDomainDiskDefFormat(virBufferPtr buf,
virBufferAddLit(buf, ">\n");
if (def->driverName || def->driverType || def->cachemode ||
- def->ioeventfd || def->event_idx) {
+ def->ioeventfd || def->event_idx || def->copy_on_read) {
virBufferAddLit(buf, " <driver");
if (def->driverName)
virBufferAsprintf(buf, " name='%s'", def->driverName);
@@ -9826,6 +9846,8 @@ virDomainDiskDefFormat(virBufferPtr buf,
virBufferAsprintf(buf, " ioeventfd='%s'", ioeventfd);
if (def->event_idx)
virBufferAsprintf(buf, " event_idx='%s'", event_idx);
+ if (def->copy_on_read)
+ virBufferAsprintf(buf, " copy_on_read='%s'", copy_on_read);
virBufferAddLit(buf, "/>\n");
}
diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
index 1f6e442..4575ab2 100644
--- a/src/conf/domain_conf.h
+++ b/src/conf/domain_conf.h
@@ -288,6 +288,14 @@ enum virDomainVirtioEventIdx {
VIR_DOMAIN_VIRTIO_EVENT_IDX_LAST
};
+enum virDomainDiskCopyOnRead {
+ VIR_DOMAIN_DISK_COPY_ON_READ_DEFAULT = 0,
+ VIR_DOMAIN_DISK_COPY_ON_READ_ON,
+ VIR_DOMAIN_DISK_COPY_ON_READ_OFF,
+
+ VIR_DOMAIN_DISK_COPY_ON_READ_LAST
+};
+
enum virDomainDiskSnapshot {
VIR_DOMAIN_DISK_SNAPSHOT_DEFAULT = 0,
VIR_DOMAIN_DISK_SNAPSHOT_NO,
@@ -363,6 +371,7 @@ struct _virDomainDiskDef {
int iomode;
int ioeventfd;
int event_idx;
+ int copy_on_read;
int snapshot; /* enum virDomainDiskSnapshot */
int startupPolicy; /* enum virDomainStartupPolicy */
unsigned int readonly : 1;
@@ -1968,6 +1977,7 @@ VIR_ENUM_DECL(virDomainDiskSecretType)
VIR_ENUM_DECL(virDomainDiskSnapshot)
VIR_ENUM_DECL(virDomainIoEventFd)
VIR_ENUM_DECL(virDomainVirtioEventIdx)
+VIR_ENUM_DECL(virDomainDiskCopyOnRead)
VIR_ENUM_DECL(virDomainController)
VIR_ENUM_DECL(virDomainControllerModelSCSI)
VIR_ENUM_DECL(virDomainControllerModelUSB)
diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index 4a86bdc..63c2947 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -290,6 +290,8 @@ virDomainDeviceTypeToString;
virDomainDiskBusTypeToString;
virDomainDiskCacheTypeFromString;
virDomainDiskCacheTypeToString;
+virDomainDiskCopyOnReadTypeFromString;
+virDomainDiskCopyOnReadTypeToString;
virDomainDiskDefAssignAddress;
virDomainDiskDefForeachPath;
virDomainDiskDefFree;
diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c
index 43c7578..f32c792 100644
--- a/src/qemu/qemu_capabilities.c
+++ b/src/qemu/qemu_capabilities.c
@@ -144,6 +144,7 @@ VIR_ENUM_IMPL(qemuCaps, QEMU_CAPS_LAST,
"ich9-ahci",
"no-acpi",
"fsdev-readonly",
+ "drive-copy-on-read",
);
struct qemu_feature_flags {
@@ -1023,6 +1024,8 @@ qemuCapsComputeCmdFlags(const char *help,
qemuCapsSet(flags, QEMU_CAPS_DRIVE_READONLY);
if (strstr(help, "aio=threads|native"))
qemuCapsSet(flags, QEMU_CAPS_DRIVE_AIO);
+ if (strstr(help, "copy-on-read=on|off"))
+ qemuCapsSet(flags, QEMU_CAPS_DRIVE_COPY_ON_READ);
}
if ((p = strstr(help, "-vga")) && !strstr(help, "-std-vga")) {
const char *nl = strstr(p, "\n");
diff --git a/src/qemu/qemu_capabilities.h b/src/qemu/qemu_capabilities.h
index c759baf..38106dd 100644
--- a/src/qemu/qemu_capabilities.h
+++ b/src/qemu/qemu_capabilities.h
@@ -117,6 +117,7 @@ enum qemuCapsFlags {
QEMU_CAPS_ICH9_AHCI = 77, /* -device ich9-ahci */
QEMU_CAPS_NO_ACPI = 78, /* -no-acpi */
QEMU_CAPS_FSDEV_READONLY =79, /* -fsdev readonly supported */
+ QEMU_CAPS_DRIVE_COPY_ON_READ = 80, /* -drive copy-on-read */
QEMU_CAPS_LAST, /* this must always be the last item */
};
diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index ea1b763..629f13d 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -1926,6 +1926,17 @@ qemuBuildDriveStr(virConnectPtr conn ATTRIBUTE_UNUSED,
virBufferAddLit(&opt, ",cache=off");
}
+ if (disk->copy_on_read) {
+ if (qemuCapsGet(qemuCaps, QEMU_CAPS_DRIVE_COPY_ON_READ)) {
+ virBufferAsprintf(&opt, ",copy-on-read=%s",
+ virDomainDiskCopyOnReadTypeToString(disk->copy_on_read));
+ } else {
+ qemuReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+ _("copy_on_read is not supported by this QEMU binary"));
+ goto error;
+ }
+ }
+
if (qemuCapsGet(qemuCaps, QEMU_CAPS_MONITOR_JSON)) {
const char *wpolicy = NULL, *rpolicy = NULL;
--
1.7.7.3
--
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