Qemu since 1.5 supports discard. However until qemu 1.6 it didn't work for qcow2 files. Ref: http://wiki.qemu.org/ChangeLog/1.5 http://wiki.qemu.org/ChangeLog/1.6 If qemu >= 1.6, add this to guest capabilities: <features> <drivediscard/> <qcow2discard/> <--- </features> --- src/conf/capabilities.c | 3 ++- src/qemu/qemu_capabilities.c | 13 +++++++++++++ src/qemu/qemu_capabilities.h | 1 + tests/qemucapabilitiesdata/caps_1.6.0-1.caps | 1 + tests/qemucapabilitiesdata/caps_1.6.50-1.caps | 1 + 5 files changed, 18 insertions(+), 1 deletion(-) diff --git a/src/conf/capabilities.c b/src/conf/capabilities.c index ff5912a..08c9b73 100644 --- a/src/conf/capabilities.c +++ b/src/conf/capabilities.c @@ -948,7 +948,8 @@ virCapabilitiesFormatXML(virCapsPtr caps) STREQ(caps->guests[i]->features[j]->name, "ia64_be") || STREQ(caps->guests[i]->features[j]->name, "cpuselection") || STREQ(caps->guests[i]->features[j]->name, "deviceboot") || - STREQ(caps->guests[i]->features[j]->name, "drivediscard")) { + STREQ(caps->guests[i]->features[j]->name, "drivediscard") || + STREQ(caps->guests[i]->features[j]->name, "qcow2discard")) { virBufferAsprintf(&xml, " <%s/>\n", caps->guests[i]->features[j]->name); } else { diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c index b755fb2..b527690 100644 --- a/src/qemu/qemu_capabilities.c +++ b/src/qemu/qemu_capabilities.c @@ -251,6 +251,7 @@ VIR_ENUM_IMPL(virQEMUCaps, QEMU_CAPS_LAST, "spiceport", "usb-kbd", /* 165 */ + "qcow2-discard", ); struct _virQEMUCaps { @@ -782,6 +783,10 @@ virQEMUCapsInitGuest(virCapsPtr caps, !virCapabilitiesAddGuestFeature(guest, "drivediscard", 0, 0)) goto error; + if (virQEMUCapsGet(qemubinCaps, QEMU_CAPS_QCOW2_DISCARD) && + !virCapabilitiesAddGuestFeature(guest, "qcow2discard", 0, 0)) + goto error; + if (virCapabilitiesAddGuestDomain(guest, "qemu", NULL, @@ -1113,6 +1118,10 @@ virQEMUCapsComputeCmdFlags(const char *help, if (strstr(help, "-machine")) virQEMUCapsSet(qemuCaps, QEMU_CAPS_MACHINE_OPT); + /* discard option works for qcow2 backing files since 1.6 */ + if (qemuCaps->version >= 1006000) + virQEMUCapsSet(qemuCaps, QEMU_CAPS_QCOW2_DISCARD); + /* USB option is supported v1.3.0 onwards */ if (qemuCaps->version >= 1003000) virQEMUCapsSet(qemuCaps, QEMU_CAPS_MACHINE_USB_OPT); @@ -2569,6 +2578,10 @@ virQEMUCapsInitQMPMonitor(virQEMUCapsPtr qemuCaps, if (virQEMUCapsInitArchQMPBasic(qemuCaps, mon) < 0) goto cleanup; + /* discard option works for qcow2 backing files since 1.6 */ + if (qemuCaps->version >= 1006000) + virQEMUCapsSet(qemuCaps, QEMU_CAPS_QCOW2_DISCARD); + /* USB option is supported v1.3.0 onwards */ if (qemuCaps->version >= 1003000) virQEMUCapsSet(qemuCaps, QEMU_CAPS_MACHINE_USB_OPT); diff --git a/src/qemu/qemu_capabilities.h b/src/qemu/qemu_capabilities.h index b5445e7..a0ce506 100644 --- a/src/qemu/qemu_capabilities.h +++ b/src/qemu/qemu_capabilities.h @@ -204,6 +204,7 @@ enum virQEMUCapsFlags { QEMU_CAPS_SPICE_FILE_XFER_DISABLE = 163, /* -spice disable-agent-file-xfer */ QEMU_CAPS_CHARDEV_SPICEPORT = 164, /* -chardev spiceport */ QEMU_CAPS_DEVICE_USB_KBD = 165, /* -device usb-kbd */ + QEMU_CAPS_QCOW2_DISCARD = 166, /* discard works for qcow2 backing files */ QEMU_CAPS_LAST, /* this must always be the last item */ }; diff --git a/tests/qemucapabilitiesdata/caps_1.6.0-1.caps b/tests/qemucapabilitiesdata/caps_1.6.0-1.caps index 597f873..0ab5e22 100644 --- a/tests/qemucapabilitiesdata/caps_1.6.0-1.caps +++ b/tests/qemucapabilitiesdata/caps_1.6.0-1.caps @@ -142,4 +142,5 @@ <flag name='spice-file-xfer-disable'/> <flag name='spiceport'/> <flag name='usb-kbd'/> + <flag name='qcow2-discard'/> </qemuCaps> diff --git a/tests/qemucapabilitiesdata/caps_1.6.50-1.caps b/tests/qemucapabilitiesdata/caps_1.6.50-1.caps index 0c1dd87..d5cca41 100644 --- a/tests/qemucapabilitiesdata/caps_1.6.50-1.caps +++ b/tests/qemucapabilitiesdata/caps_1.6.50-1.caps @@ -140,4 +140,5 @@ <flag name='spice-file-xfer-disable'/> <flag name='spiceport'/> <flag name='usb-kbd'/> + <flag name='qcow2-discard'/> </qemuCaps> -- 1.8.5.3