[PATCH] Allow specifying zero discard granularity for block devices
From: Martin Kletzander <mkletzan@redhat.com> That allows for disabling discard in a way that some guest OSes (e.g. Windows) understand and do not try to trim the disk. Resolves: https://issues.redhat.com/browse/RHEL-72006 Signed-off-by: Martin Kletzander <mkletzan@redhat.com> --- Out of all the approaches for allowing previously default value 100% of them are ugly. This one is maybe slightly more error-prone. src/conf/domain_conf.c | 12 ++++++++---- src/conf/domain_conf.h | 1 + src/conf/domain_validate.c | 2 +- src/qemu/qemu_command.c | 7 ++++++- tests/qemuxmlconftest.c | 1 + 5 files changed, 17 insertions(+), 6 deletions(-) diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c index bfc62b62705f..ba0d4a7b128c 100644 --- a/src/conf/domain_conf.c +++ b/src/conf/domain_conf.c @@ -8554,6 +8554,8 @@ virDomainDiskDefParseXML(virDomainXMLOption *xmlopt, } if ((blockioNode = virXPathNode("./blockio", ctxt))) { + int tmp = 0; + if (virXMLPropUInt(blockioNode, "logical_block_size", 10, VIR_XML_PROP_NONE, &def->blockio.logical_block_size) < 0) return NULL; @@ -8562,9 +8564,11 @@ virDomainDiskDefParseXML(virDomainXMLOption *xmlopt, &def->blockio.physical_block_size) < 0) return NULL; - if (virXMLPropUInt(blockioNode, "discard_granularity", 10, VIR_XML_PROP_NONE, - &def->blockio.discard_granularity) < 0) + if ((tmp = virXMLPropUInt(blockioNode, "discard_granularity", 10, VIR_XML_PROP_NONE, + &def->blockio.discard_granularity)) < 0) return NULL; + if (tmp > 0) + def->blockio.discard_granularity_specified = true; } if ((driverNode = virXPathNode("./driver", ctxt))) { @@ -23102,7 +23106,7 @@ virDomainDiskBlockIoDefFormat(virBuffer *buf, { if (def->blockio.logical_block_size > 0 || def->blockio.physical_block_size > 0 || - def->blockio.discard_granularity > 0) { + def->blockio.discard_granularity_specified) { virBufferAddLit(buf, "<blockio"); if (def->blockio.logical_block_size > 0) { virBufferAsprintf(buf, @@ -23114,7 +23118,7 @@ virDomainDiskBlockIoDefFormat(virBuffer *buf, " physical_block_size='%u'", def->blockio.physical_block_size); } - if (def->blockio.discard_granularity > 0) { + if (def->blockio.discard_granularity_specified) { virBufferAsprintf(buf, " discard_granularity='%u'", def->blockio.discard_granularity); diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h index 6997cf7c09be..6008ec66d3fe 100644 --- a/src/conf/domain_conf.h +++ b/src/conf/domain_conf.h @@ -560,6 +560,7 @@ struct _virDomainDiskDef { unsigned int logical_block_size; unsigned int physical_block_size; unsigned int discard_granularity; + bool discard_granularity_specified; } blockio; virDomainBlockIoTuneInfo blkdeviotune; diff --git a/src/conf/domain_validate.c b/src/conf/domain_validate.c index b28af7fa5618..8f7259a0e1ed 100644 --- a/src/conf/domain_validate.c +++ b/src/conf/domain_validate.c @@ -462,7 +462,7 @@ virDomainDiskVhostUserValidate(const virDomainDiskDef *disk) if (disk->blockio.logical_block_size > 0 || disk->blockio.physical_block_size > 0 || - disk->blockio.discard_granularity > 0) { + disk->blockio.discard_granularity_specified) { virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s", _("blockio is not supported with vhostuser disk")); return -1; diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c index 7658cc4d395a..fc6ce4dd9143 100644 --- a/src/qemu/qemu_command.c +++ b/src/qemu/qemu_command.c @@ -1899,7 +1899,6 @@ qemuBuildDiskDeviceProps(const virDomainDef *def, "S:loadparm", bootLoadparm, "p:logical_block_size", logical_block_size, "p:physical_block_size", physical_block_size, - "p:discard_granularity", discard_granularity, "A:wwn", &wwn, "p:rotation_rate", disk->rotation_rate, "S:vendor", disk->vendor, @@ -1917,6 +1916,12 @@ qemuBuildDiskDeviceProps(const virDomainDef *def, NULL) < 0) return NULL; + if (disk->blockio.discard_granularity_specified && + virJSONValueObjectAdd(&props, + "u:discard_granularity", discard_granularity, + NULL) < 0) + return NULL; + return g_steal_pointer(&props); } diff --git a/tests/qemuxmlconftest.c b/tests/qemuxmlconftest.c index 9fba98429019..ae8efd58f8ac 100644 --- a/tests/qemuxmlconftest.c +++ b/tests/qemuxmlconftest.c @@ -1694,6 +1694,7 @@ mymain(void) DO_TEST_CAPS_LATEST("disk-ide-wwn"); DO_TEST_CAPS_LATEST("disk-geometry"); DO_TEST_CAPS_LATEST("disk-blockio"); + DO_TEST_CAPS_LATEST("disk-blockio-no-discard"); driver.config->storageUseNbdkit = 1; DO_TEST_CAPS_LATEST_NBDKIT("disk-cdrom-network-nbdkit", QEMU_NBDKIT_CAPS_PLUGIN_CURL); -- 2.50.1
On Thu, Jul 17, 2025 at 03:14:36PM +0200, Martin Kletzander wrote:
From: Martin Kletzander <mkletzan@redhat.com>
That allows for disabling discard in a way that some guest OSes (e.g. Windows) understand and do not try to trim the disk.
Resolves: https://issues.redhat.com/browse/RHEL-72006 Signed-off-by: Martin Kletzander <mkletzan@redhat.com> --- Out of all the approaches for allowing previously default value 100% of them are ugly. This one is maybe slightly more error-prone.
And then I forgot to add the tests, I have the following already applied locally: diff --git c/tests/qemuxmlconfdata/disk-blockio-no-discard.x86_64-latest.args w/tests/qemuxmlconfdata/disk-blockio-no-discard.x86_64-latest.args new file mode 100644 index 000000000000..0e477c6e40de --- /dev/null +++ w/tests/qemuxmlconfdata/disk-blockio-no-discard.x86_64-latest.args @@ -0,0 +1,37 @@ +LC_ALL=C \ +PATH=/bin \ +HOME=/var/lib/libvirt/qemu/domain--1-QEMUGuest1 \ +USER=test \ +LOGNAME=test \ +XDG_DATA_HOME=/var/lib/libvirt/qemu/domain--1-QEMUGuest1/.local/share \ +XDG_CACHE_HOME=/var/lib/libvirt/qemu/domain--1-QEMUGuest1/.cache \ +XDG_CONFIG_HOME=/var/lib/libvirt/qemu/domain--1-QEMUGuest1/.config \ +/usr/bin/qemu-system-x86_64 \ +-name guest=QEMUGuest1,debug-threads=on \ +-S \ +-object '{"qom-type":"secret","id":"masterKey0","format":"raw","file":"/var/lib/libvirt/qemu/domain--1-QEMUGuest1/master-key.aes"}' \ +-machine pc,usb=off,dump-guest-core=off,memory-backend=pc.ram,acpi=off \ +-accel tcg \ +-cpu qemu64 \ +-m size=219136k \ +-object '{"qom-type":"memory-backend-ram","id":"pc.ram","size":224395264}' \ +-overcommit mem-lock=off \ +-smp 1,sockets=1,cores=1,threads=1 \ +-uuid c7a5fdbd-edaf-9455-926a-d65c16db1809 \ +-display none \ +-no-user-config \ +-nodefaults \ +-chardev socket,id=charmonitor,fd=1729,server=on,wait=off \ +-mon chardev=charmonitor,id=monitor,mode=control \ +-rtc base=utc \ +-no-shutdown \ +-boot strict=on \ +-device '{"driver":"piix3-usb-uhci","id":"usb","bus":"pci.0","addr":"0x1.0x2"}' \ +-blockdev '{"driver":"host_device","filename":"/dev/HostVG/QEMUGuest1","node-name":"libvirt-2-storage","read-only":true}' \ +-device '{"driver":"ide-cd","bus":"ide.0","unit":1,"drive":"libvirt-2-storage","id":"ide0-0-1"}' \ +-blockdev '{"driver":"file","filename":"/tmp/idedisk.img","node-name":"libvirt-1-storage","read-only":false}' \ +-device '{"driver":"ide-hd","bus":"ide.0","unit":2,"drive":"libvirt-1-storage","id":"ide0-0-2","bootindex":1,"logical_block_size":512,"physical_block_size":512,"discard_granularity":0}' \ +-audiodev '{"id":"audio1","driver":"none"}' \ +-device '{"driver":"virtio-balloon-pci","id":"balloon0","bus":"pci.0","addr":"0x2"}' \ +-sandbox on,obsolete=deny,elevateprivileges=deny,spawn=deny,resourcecontrol=deny \ +-msg timestamp=on diff --git c/tests/qemuxmlconfdata/disk-blockio-no-discard.x86_64-latest.xml w/tests/qemuxmlconfdata/disk-blockio-no-discard.x86_64-latest.xml new file mode 100644 index 000000000000..94cff1ce6a18 --- /dev/null +++ w/tests/qemuxmlconfdata/disk-blockio-no-discard.x86_64-latest.xml @@ -0,0 +1,48 @@ +<domain type='qemu'> + <name>QEMUGuest1</name> + <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid> + <memory unit='KiB'>219136</memory> + <currentMemory unit='KiB'>219136</currentMemory> + <vcpu placement='static'>1</vcpu> + <os> + <type arch='x86_64' machine='pc'>hvm</type> + <boot dev='hd'/> + </os> + <cpu mode='custom' match='exact' check='none'> + <model fallback='forbid'>qemu64</model> + </cpu> + <clock offset='utc'/> + <on_poweroff>destroy</on_poweroff> + <on_reboot>restart</on_reboot> + <on_crash>destroy</on_crash> + <devices> + <emulator>/usr/bin/qemu-system-x86_64</emulator> + <disk type='block' device='cdrom'> + <driver name='qemu' type='raw'/> + <source dev='/dev/HostVG/QEMUGuest1'/> + <target dev='hda' bus='ide'/> + <readonly/> + <address type='drive' controller='0' bus='0' target='0' unit='1'/> + </disk> + <disk type='file' device='disk'> + <driver name='qemu' type='raw'/> + <source file='/tmp/idedisk.img'/> + <blockio logical_block_size='512' physical_block_size='512' discard_granularity='0'/> + <target dev='hdc' bus='ide'/> + <address type='drive' controller='0' bus='0' target='0' unit='2'/> + </disk> + <controller type='usb' index='0' model='piix3-uhci'> + <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/> + </controller> + <controller type='ide' index='0'> + <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/> + </controller> + <controller type='pci' index='0' model='pci-root'/> + <input type='mouse' bus='ps2'/> + <input type='keyboard' bus='ps2'/> + <audio id='1' type='none'/> + <memballoon model='virtio'> + <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/> + </memballoon> + </devices> +</domain> diff --git c/tests/qemuxmlconfdata/disk-blockio-no-discard.xml w/tests/qemuxmlconfdata/disk-blockio-no-discard.xml new file mode 100644 index 000000000000..600022391512 --- /dev/null +++ w/tests/qemuxmlconfdata/disk-blockio-no-discard.xml @@ -0,0 +1,32 @@ +<domain type='qemu'> + <name>QEMUGuest1</name> + <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid> + <memory unit='KiB'>219136</memory> + <currentMemory unit='KiB'>219136</currentMemory> + <vcpu placement='static'>1</vcpu> + <os> + <type arch='x86_64' machine='pc'>hvm</type> + <boot dev='hd'/> + </os> + <clock offset='utc'/> + <on_poweroff>destroy</on_poweroff> + <on_reboot>restart</on_reboot> + <on_crash>destroy</on_crash> + <devices> + <emulator>/usr/bin/qemu-system-x86_64</emulator> + <disk type='block' device='cdrom'> + <source dev='/dev/HostVG/QEMUGuest1'/> + <target dev='hda' bus='ide'/> + <address type='drive' controller='0' bus='0' target='0' unit='1'/> + </disk> + <disk type='file' device='disk'> + <source file='/tmp/idedisk.img'/> + <target dev='hdc' bus='ide'/> + <address type='drive' controller='0' bus='0' target='0' unit='2'/> + <blockio logical_block_size='512' physical_block_size='512' discard_granularity='0'/> + </disk> + <controller type='usb' index='0'/> + <controller type='ide' index='0'/> + <memballoon model='virtio'/> + </devices> +</domain>
src/conf/domain_conf.c | 12 ++++++++---- src/conf/domain_conf.h | 1 + src/conf/domain_validate.c | 2 +- src/qemu/qemu_command.c | 7 ++++++- tests/qemuxmlconftest.c | 1 + 5 files changed, 17 insertions(+), 6 deletions(-)
diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c index bfc62b62705f..ba0d4a7b128c 100644 --- a/src/conf/domain_conf.c +++ b/src/conf/domain_conf.c @@ -8554,6 +8554,8 @@ virDomainDiskDefParseXML(virDomainXMLOption *xmlopt, }
if ((blockioNode = virXPathNode("./blockio", ctxt))) { + int tmp = 0; + if (virXMLPropUInt(blockioNode, "logical_block_size", 10, VIR_XML_PROP_NONE, &def->blockio.logical_block_size) < 0) return NULL; @@ -8562,9 +8564,11 @@ virDomainDiskDefParseXML(virDomainXMLOption *xmlopt, &def->blockio.physical_block_size) < 0) return NULL;
- if (virXMLPropUInt(blockioNode, "discard_granularity", 10, VIR_XML_PROP_NONE, - &def->blockio.discard_granularity) < 0) + if ((tmp = virXMLPropUInt(blockioNode, "discard_granularity", 10, VIR_XML_PROP_NONE, + &def->blockio.discard_granularity)) < 0) return NULL; + if (tmp > 0) + def->blockio.discard_granularity_specified = true; }
if ((driverNode = virXPathNode("./driver", ctxt))) { @@ -23102,7 +23106,7 @@ virDomainDiskBlockIoDefFormat(virBuffer *buf, { if (def->blockio.logical_block_size > 0 || def->blockio.physical_block_size > 0 || - def->blockio.discard_granularity > 0) { + def->blockio.discard_granularity_specified) { virBufferAddLit(buf, "<blockio"); if (def->blockio.logical_block_size > 0) { virBufferAsprintf(buf, @@ -23114,7 +23118,7 @@ virDomainDiskBlockIoDefFormat(virBuffer *buf, " physical_block_size='%u'", def->blockio.physical_block_size); } - if (def->blockio.discard_granularity > 0) { + if (def->blockio.discard_granularity_specified) { virBufferAsprintf(buf, " discard_granularity='%u'", def->blockio.discard_granularity); diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h index 6997cf7c09be..6008ec66d3fe 100644 --- a/src/conf/domain_conf.h +++ b/src/conf/domain_conf.h @@ -560,6 +560,7 @@ struct _virDomainDiskDef { unsigned int logical_block_size; unsigned int physical_block_size; unsigned int discard_granularity; + bool discard_granularity_specified; } blockio;
virDomainBlockIoTuneInfo blkdeviotune; diff --git a/src/conf/domain_validate.c b/src/conf/domain_validate.c index b28af7fa5618..8f7259a0e1ed 100644 --- a/src/conf/domain_validate.c +++ b/src/conf/domain_validate.c @@ -462,7 +462,7 @@ virDomainDiskVhostUserValidate(const virDomainDiskDef *disk)
if (disk->blockio.logical_block_size > 0 || disk->blockio.physical_block_size > 0 || - disk->blockio.discard_granularity > 0) { + disk->blockio.discard_granularity_specified) { virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s", _("blockio is not supported with vhostuser disk")); return -1; diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c index 7658cc4d395a..fc6ce4dd9143 100644 --- a/src/qemu/qemu_command.c +++ b/src/qemu/qemu_command.c @@ -1899,7 +1899,6 @@ qemuBuildDiskDeviceProps(const virDomainDef *def, "S:loadparm", bootLoadparm, "p:logical_block_size", logical_block_size, "p:physical_block_size", physical_block_size, - "p:discard_granularity", discard_granularity, "A:wwn", &wwn, "p:rotation_rate", disk->rotation_rate, "S:vendor", disk->vendor, @@ -1917,6 +1916,12 @@ qemuBuildDiskDeviceProps(const virDomainDef *def, NULL) < 0) return NULL;
+ if (disk->blockio.discard_granularity_specified && + virJSONValueObjectAdd(&props, + "u:discard_granularity", discard_granularity, + NULL) < 0) + return NULL; + return g_steal_pointer(&props); }
diff --git a/tests/qemuxmlconftest.c b/tests/qemuxmlconftest.c index 9fba98429019..ae8efd58f8ac 100644 --- a/tests/qemuxmlconftest.c +++ b/tests/qemuxmlconftest.c @@ -1694,6 +1694,7 @@ mymain(void) DO_TEST_CAPS_LATEST("disk-ide-wwn"); DO_TEST_CAPS_LATEST("disk-geometry"); DO_TEST_CAPS_LATEST("disk-blockio"); + DO_TEST_CAPS_LATEST("disk-blockio-no-discard");
driver.config->storageUseNbdkit = 1; DO_TEST_CAPS_LATEST_NBDKIT("disk-cdrom-network-nbdkit", QEMU_NBDKIT_CAPS_PLUGIN_CURL); -- 2.50.1
On a Thursday in 2025, Martin Kletzander via Devel wrote:
On Thu, Jul 17, 2025 at 03:14:36PM +0200, Martin Kletzander wrote:
From: Martin Kletzander <mkletzan@redhat.com>
That allows for disabling discard in a way that some guest OSes (e.g. Windows) understand and do not try to trim the disk.
Resolves: https://issues.redhat.com/browse/RHEL-72006 Signed-off-by: Martin Kletzander <mkletzan@redhat.com> --- Out of all the approaches for allowing previously default value 100% of them are ugly. This one is maybe slightly more error-prone.
And then I forgot to add the tests, I have the following already applied locally:
Please use git-send-email for sending patches, see: https://libvirt.org/submitting-patches.html Jano
On Thu, Jul 17, 2025 at 15:14:36 +0200, Martin Kletzander via Devel wrote:
From: Martin Kletzander <mkletzan@redhat.com>
That allows for disabling discard in a way that some guest OSes (e.g. Windows) understand and do not try to trim the disk.
Resolves: https://issues.redhat.com/browse/RHEL-72006 Signed-off-by: Martin Kletzander <mkletzan@redhat.com> --- Out of all the approaches for allowing previously default value 100% of them are ugly. This one is maybe slightly more error-prone.
src/conf/domain_conf.c | 12 ++++++++---- src/conf/domain_conf.h | 1 + src/conf/domain_validate.c | 2 +- src/qemu/qemu_command.c | 7 ++++++- tests/qemuxmlconftest.c | 1 + 5 files changed, 17 insertions(+), 6 deletions(-)
Reviewed-by: Peter Krempa <pkrempa@redhat.com>
participants (3)
-
Ján Tomko -
Martin Kletzander -
Peter Krempa