qemu: Add support for zero-detection writes

Signed-off-by: Martin Kletzander <mkletzan@redhat.com>

src/qemu/qemu_capabilities.c

@@ -333,6 +333,7 @@ VIR_ENUM_IMPL(virQEMUCaps, QEMU_CAPS_LAST,
               "qxl.max_outputs", /* 225 */
               "qxl-vga.max_outputs",
               "spice-unix",
+              "drive-detect-zeroes",
     );
 
 
@@ -2650,6 +2651,7 @@ static struct virQEMUCapsCommandLineProps virQEMUCapsCommandLine[] = {
     { "machine", "mem-merge", QEMU_CAPS_MEM_MERGE },
     { "machine", "vmport", QEMU_CAPS_MACHINE_VMPORT_OPT },
     { "drive", "discard", QEMU_CAPS_DRIVE_DISCARD },
+    { "drive", "detect-zeroes", QEMU_CAPS_DRIVE_DETECT_ZEROES },
     { "realtime", "mlock", QEMU_CAPS_MLOCK },
     { "boot-opts", "strict", QEMU_CAPS_BOOT_STRICT },
     { "boot-opts", "reboot-timeout", QEMU_CAPS_REBOOT_TIMEOUT },

src/qemu/qemu_capabilities.h

@@ -366,6 +366,7 @@ typedef enum {
     QEMU_CAPS_QXL_MAX_OUTPUTS, /* -device qxl,max-outputs= */
     QEMU_CAPS_QXL_VGA_MAX_OUTPUTS, /* -device qxl-vga,max-outputs= */
     QEMU_CAPS_SPICE_UNIX, /* -spice unix */
+    QEMU_CAPS_DRIVE_DETECT_ZEROES, /* -drive detect-zeroes= */
 
     QEMU_CAPS_LAST /* this must always be the last item */
 } virQEMUCapsFlags;

src/qemu/qemu_command.c

@@ -1391,6 +1391,30 @@ qemuBuildDriveStr(virDomainDiskDefPtr disk,
         }
     }
 
+    if (disk->detect_zeroes) {
+        if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_DRIVE_DETECT_ZEROES)) {
+            int detect_zeroes = disk->detect_zeroes;
+
+            /*
+             * As a convenience syntax, if discards are ignored and
+             * zero detection is set to 'unmap', then simply behave
+             * like zero detection is set to 'on'.  But don't change
+             * it in the XML for easier adjustments.  This behaviour
+             * is documented.
+             */
+            if (disk->discard != VIR_DOMAIN_DISK_DISCARD_UNMAP &&
+                detect_zeroes == VIR_DOMAIN_DISK_DETECT_ZEROES_UNMAP)
+                detect_zeroes = VIR_DOMAIN_DISK_DETECT_ZEROES_ON;
+
+            virBufferAsprintf(&opt, ",detect-zeroes=%s",
+                              virDomainDiskDetectZeroesTypeToString(detect_zeroes));
+        } else {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                           _("detect_zeroes is not supported by this QEMU binary"));
+            goto error;
+        }
+    }
+
     if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_MONITOR_JSON)) {
         const char *wpolicy = NULL, *rpolicy = NULL;
 

tests/qemucapabilitiesdata/caps_2.1.1.x86_64.xml

@@ -164,6 +164,7 @@
   <flag name='device-tray-moved-event'/>
   <flag name='nec-usb-xhci-ports'/>
   <flag name='name-guest'/>
+  <flag name='drive-detect-zeroes'/>
   <version>2001001</version>
   <kvmVersion>0</kvmVersion>
   <package></package>

tests/qemucapabilitiesdata/caps_2.4.0.x86_64.xml

@@ -181,6 +181,7 @@
   <flag name='qxl.max_outputs'/>
   <flag name='qxl-vga.max_outputs'/>
   <flag name='spice-unix'/>
+  <flag name='drive-detect-zeroes'/>
   <version>2004000</version>
   <kvmVersion>0</kvmVersion>
   <package></package>

tests/qemucapabilitiesdata/caps_2.5.0.x86_64.xml

@@ -185,6 +185,7 @@
   <flag name='qxl.max_outputs'/>
   <flag name='qxl-vga.max_outputs'/>
   <flag name='spice-unix'/>
+  <flag name='drive-detect-zeroes'/>
   <version>2005000</version>
   <kvmVersion>0</kvmVersion>
   <package></package>

tests/qemucapabilitiesdata/caps_2.6.0-gicv2.aarch64.xml

@@ -155,6 +155,7 @@
   <flag name='nec-usb-xhci-ports'/>
   <flag name='virtio-scsi-pci.iothread'/>
   <flag name='name-guest'/>
+  <flag name='drive-detect-zeroes'/>
   <version>2005094</version>
   <kvmVersion>0</kvmVersion>
   <package></package>

tests/qemucapabilitiesdata/caps_2.6.0-gicv3.aarch64.xml

@@ -155,6 +155,7 @@
   <flag name='nec-usb-xhci-ports'/>
   <flag name='virtio-scsi-pci.iothread'/>
   <flag name='name-guest'/>
+  <flag name='drive-detect-zeroes'/>
   <version>2005094</version>
   <kvmVersion>0</kvmVersion>
   <package></package>

tests/qemucapabilitiesdata/caps_2.6.0.ppc64le.xml

@@ -149,6 +149,7 @@
   <flag name='nec-usb-xhci-ports'/>
   <flag name='virtio-scsi-pci.iothread'/>
   <flag name='name-guest'/>
+  <flag name='drive-detect-zeroes'/>
   <version>2005094</version>
   <kvmVersion>0</kvmVersion>
   <package></package>

tests/qemucapabilitiesdata/caps_2.6.0.x86_64.xml

@@ -191,6 +191,7 @@
   <flag name='qxl.max_outputs'/>
   <flag name='qxl-vga.max_outputs'/>
   <flag name='spice-unix'/>
+  <flag name='drive-detect-zeroes'/>
   <version>2006000</version>
   <kvmVersion>0</kvmVersion>
   <package></package>

tests/qemuxml2argvdata/qemuxml2argv-disk-drive-detect-zeroes.args

@@ -0,0 +1,27 @@
+LC_ALL=C \
+PATH=/bin \
+HOME=/home/test \
+USER=test \
+LOGNAME=test \
+QEMU_AUDIO_DRV=none \
+/usr/bin/qemu \
+-name test \
+-S \
+-M pc-0.13 \
+-m 1024 \
+-smp 1 \
+-uuid 92d7a226-cfae-425b-a6d3-00bbf9ec5c9e \
+-nographic \
+-nodefaults \
+-monitor unix:/tmp/lib/domain--1-test/monitor.sock,server,nowait \
+-no-acpi \
+-boot dc \
+-usb \
+-drive file=/var/lib/libvirt/images/f14.img,format=qcow2,if=none,\
+id=drive-virtio-disk0,discard=unmap,detect-zeroes=unmap \
+-device virtio-blk-pci,bus=pci.0,addr=0x4,drive=drive-virtio-disk0,\
+id=virtio-disk0 \
+-drive file=/var/lib/libvirt/Fedora-14-x86_64-Live-KDE.iso,format=raw,if=none,\
+media=cdrom,id=drive-ide0-1-0,readonly=on,discard=ignore,detect-zeroes=on \
+-device ide-drive,bus=ide.1,unit=0,drive=drive-ide0-1-0,id=ide0-1-0 \
+-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3

tests/qemuxml2argvdata/qemuxml2argv-disk-drive-detect-zeroes.xml

@@ -23,7 +23,7 @@
       <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
     </disk>
     <disk type='file' device='cdrom'>
-      <driver discard='ignore' detect_zeroes='off'/>
+      <driver discard='ignore' detect_zeroes='unmap'/>
       <source file='/var/lib/libvirt/Fedora-14-x86_64-Live-KDE.iso'/>
       <target dev='hdc' bus='ide'/>
       <readonly/>

tests/qemuxml2argvtest.c

@@ -875,6 +875,9 @@ mymain(void)
             QEMU_CAPS_VIRTIO_BLK_SCSI);
     DO_TEST("disk-drive-discard",
             QEMU_CAPS_DRIVE_DISCARD);
+    DO_TEST("disk-drive-detect-zeroes",
+            QEMU_CAPS_DRIVE_DISCARD,
+            QEMU_CAPS_DRIVE_DETECT_ZEROES);
     DO_TEST("disk-snapshot", NONE);
     DO_TEST_PARSE_ERROR("disk-same-targets",
                         QEMU_CAPS_SCSI_LSI,