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[libvirt] [PATCHv2] Add unsafe cache mode support for disk driver



QEMU 0.13 introduced cache=unsafe for -drive, this patch exposes
it in the libvirt layer.

  * Introduced a new QEMU capability flag ($prefix_CACHE_UNSAFE),
    as even if $prefix_CACHE_V2 is set, we can't known if unsafe
    is supported.

  * qemuhelptest prints test case name on failure.
---
 Updated patch based on Osier Yang's comments and rebased it to 3abadf82

 docs/formatdomain.html.in                          |    7 ++--
 docs/schemas/domaincommon.rng                      |    1 +
 src/conf/domain_conf.c                             |    3 +-
 src/conf/domain_conf.h                             |    1 +
 src/qemu/qemu_capabilities.c                       |    4 ++
 src/qemu/qemu_capabilities.h                       |    2 +
 src/qemu/qemu_command.c                            |   14 +++++++-
 tests/qemuargv2xmltest.c                           |    1 +
 tests/qemuhelptest.c                               |   19 ++++++-----
 .../qemuxml2argv-disk-drive-cache-unsafe.args      |    5 +++
 .../qemuxml2argv-disk-drive-cache-unsafe.xml       |   33 ++++++++++++++++++++
 tests/qemuxml2argvtest.c                           |    3 ++
 tools/virsh.pod                                    |    4 +-
 13 files changed, 81 insertions(+), 16 deletions(-)
 create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-disk-drive-cache-unsafe.args
 create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-disk-drive-cache-unsafe.xml

diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
index 0a7abaf..8087327 100644
--- a/docs/formatdomain.html.in
+++ b/docs/formatdomain.html.in
@@ -996,9 +996,10 @@
           <li>
             The optional <code>cache</code> attribute controls the
             cache mechanism, possible values are "default", "none",
-            "writethrough", "writeback", and "directsync". "directsync"
-            is like "writethrough", but it bypasses the host page
-            cache.
+            "writethrough", "writeback", "directsync" (like
+            "writethrough", but it bypasses the host page cache) and
+            "unsafe" (host may cache all disk io and sync requests from
+            guest are ignored).
             <span class="since">Since 0.6.0</span>
           </li>
           <li>
diff --git a/docs/schemas/domaincommon.rng b/docs/schemas/domaincommon.rng
index d0da41c..be98be0 100644
--- a/docs/schemas/domaincommon.rng
+++ b/docs/schemas/domaincommon.rng
@@ -848,6 +848,7 @@
         <value>writeback</value>
         <value>writethrough</value>
         <value>directsync</value>
+        <value>unsafe</value>
       </choice>
     </attribute>
   </define>
diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index eebcba0..f38c1d8 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -164,7 +164,8 @@ VIR_ENUM_IMPL(virDomainDiskCache, VIR_DOMAIN_DISK_CACHE_LAST,
               "none",
               "writethrough",
               "writeback",
-              "directsync")
+              "directsync",
+              "unsafe")
 
 VIR_ENUM_IMPL(virDomainDiskErrorPolicy, VIR_DOMAIN_DISK_ERROR_POLICY_LAST,
               "default",
diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
index 371f270..86b4c79 100644
--- a/src/conf/domain_conf.h
+++ b/src/conf/domain_conf.h
@@ -192,6 +192,7 @@ enum  virDomainDiskCache {
     VIR_DOMAIN_DISK_CACHE_WRITETHRU,
     VIR_DOMAIN_DISK_CACHE_WRITEBACK,
     VIR_DOMAIN_DISK_CACHE_DIRECTSYNC,
+    VIR_DOMAIN_DISK_CACHE_UNSAFE,
 
     VIR_DOMAIN_DISK_CACHE_LAST
 };
diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c
index 850d46e..fcb9c8b 100644
--- a/src/qemu/qemu_capabilities.c
+++ b/src/qemu/qemu_capabilities.c
@@ -137,6 +137,8 @@ VIR_ENUM_IMPL(qemuCaps, QEMU_CAPS_LAST,
               "usb-redir",
               "usb-hub",
               "no-shutdown",
+
+              "cache-unsafe", /* 75 */
     );
 
 struct qemu_feature_flags {
@@ -918,6 +920,8 @@ qemuCapsComputeCmdFlags(const char *help,
             qemuCapsSet(flags, QEMU_CAPS_DRIVE_CACHE_V2);
             if (strstr(help, "directsync"))
                 qemuCapsSet(flags, QEMU_CAPS_DRIVE_CACHE_DIRECTSYNC);
+            if (strstr(help, "|unsafe"))
+                qemuCapsSet(flags, QEMU_CAPS_DRIVE_CACHE_UNSAFE);
         }
         if (strstr(help, "format="))
             qemuCapsSet(flags, QEMU_CAPS_DRIVE_FORMAT);
diff --git a/src/qemu/qemu_capabilities.h b/src/qemu/qemu_capabilities.h
index 74d3ab2..ae3de90 100644
--- a/src/qemu/qemu_capabilities.h
+++ b/src/qemu/qemu_capabilities.h
@@ -112,6 +112,8 @@ enum qemuCapsFlags {
     QEMU_CAPS_USB_HUB           = 73, /* -device usb-hub */
     QEMU_CAPS_NO_SHUTDOWN       = 74, /* usable -no-shutdown */
 
+    QEMU_CAPS_DRIVE_CACHE_UNSAFE = 75, /* Is cache=unsafe supported? */
+
     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 0adc56a..9174a5f 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -66,14 +66,16 @@ VIR_ENUM_IMPL(qemuDiskCacheV1, VIR_DOMAIN_DISK_CACHE_LAST,
               "off",
               "off",  /* writethrough not supported, so for safety, disable */
               "on",   /* Old 'on' was equivalent to 'writeback' */
-              "off"); /* directsync not supported, for safety, disable */
+              "off",  /* directsync not supported, for safety, disable */
+              "off"); /* unsafe not supported, for safety, disable */
 
 VIR_ENUM_IMPL(qemuDiskCacheV2, VIR_DOMAIN_DISK_CACHE_LAST,
               "default",
               "none",
               "writethrough",
               "writeback",
-              "directsync");
+              "directsync",
+              "unsafe");
 
 VIR_ENUM_DECL(qemuVideo)
 
@@ -1622,6 +1624,12 @@ qemuBuildDriveStr(virDomainDiskDefPtr disk,
                                 _("disk cache mode 'directsync' is not "
                                   "supported by this QEMU"));
                 goto error;
+            } else if (disk->cachemode == VIR_DOMAIN_DISK_CACHE_UNSAFE &&
+                !qemuCapsGet(qemuCaps, QEMU_CAPS_DRIVE_CACHE_UNSAFE)) {
+                qemuReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                                _("disk cache mode 'unsafe' is not "
+                                  "supported by this QEMU"));
+                goto error;
             }
         } else {
             mode = qemuDiskCacheV1TypeToString(disk->cachemode);
@@ -5536,6 +5544,8 @@ qemuParseCommandLineDisk(virCapsPtr caps,
                 def->cachemode = VIR_DOMAIN_DISK_CACHE_WRITETHRU;
             else if (STREQ(values[i], "directsync"))
                 def->cachemode = VIR_DOMAIN_DISK_CACHE_DIRECTSYNC;
+            else if (STREQ(values[i], "unsafe"))
+                def->cachemode = VIR_DOMAIN_DISK_CACHE_UNSAFE;
         } else if (STREQ(keywords[i], "werror") ||
                    STREQ(keywords[i], "rerror")) {
             if (STREQ(values[i], "stop"))
diff --git a/tests/qemuargv2xmltest.c b/tests/qemuargv2xmltest.c
index 91f15af..6a79630 100644
--- a/tests/qemuargv2xmltest.c
+++ b/tests/qemuargv2xmltest.c
@@ -169,6 +169,7 @@ mymain(void)
     DO_TEST("disk-drive-cache-v2-wb");
     DO_TEST("disk-drive-cache-v2-none");
     DO_TEST("disk-drive-cache-directsync");
+    DO_TEST("disk-drive-cache-unsafe");
     DO_TEST("disk-drive-network-nbd");
     DO_TEST("disk-drive-network-rbd");
     DO_TEST("disk-drive-network-sheepdog");
diff --git a/tests/qemuhelptest.c b/tests/qemuhelptest.c
index 4a4070a..0ff8236 100644
--- a/tests/qemuhelptest.c
+++ b/tests/qemuhelptest.c
@@ -77,8 +77,8 @@ static int testHelpStrParsing(const void *data)
 
     if (STRNEQ(got, expected)) {
         fprintf(stderr,
-                "Computed flags do not match: got %s, expected %s\n",
-                got, expected);
+                "%s: computed flags do not match: got %s, expected %s\n",
+                info->name, got, expected);
 
         if (getenv("VIR_TEST_DEBUG"))
             printMismatchedFlags(flags, info->flags);
@@ -87,22 +87,22 @@ static int testHelpStrParsing(const void *data)
     }
 
     if (version != info->version) {
-        fprintf(stderr, "Parsed versions do not match: got %u, expected %u\n",
-                version, info->version);
+        fprintf(stderr, "%s: parsed versions do not match: got %u, expected %u\n",
+                info->name, version, info->version);
         goto cleanup;
     }
 
     if (is_kvm != info->is_kvm) {
         fprintf(stderr,
-                "Parsed is_kvm flag does not match: got %u, expected %u\n",
-                is_kvm, info->is_kvm);
+                "%s: parsed is_kvm flag does not match: got %u, expected %u\n",
+                info->name, is_kvm, info->is_kvm);
         goto cleanup;
     }
 
     if (kvm_version != info->kvm_version) {
         fprintf(stderr,
-                "Parsed KVM versions do not match: got %u, expected %u\n",
-                kvm_version, info->kvm_version);
+                "%s: parsed KVM versions do not match: got %u, expected %u\n",
+                info->name, kvm_version, info->kvm_version);
         goto cleanup;
     }
 
@@ -165,6 +165,7 @@ mymain(void)
             QEMU_CAPS_MIGRATE_QEMU_TCP,
             QEMU_CAPS_MIGRATE_QEMU_EXEC,
             QEMU_CAPS_DRIVE_CACHE_V2,
+            QEMU_CAPS_DRIVE_CACHE_UNSAFE,
             QEMU_CAPS_KVM,
             QEMU_CAPS_DRIVE_FORMAT,
             QEMU_CAPS_DRIVE_SERIAL,
@@ -408,6 +409,7 @@ mymain(void)
             QEMU_CAPS_MIGRATE_QEMU_TCP,
             QEMU_CAPS_MIGRATE_QEMU_EXEC,
             QEMU_CAPS_DRIVE_CACHE_V2,
+            QEMU_CAPS_DRIVE_CACHE_UNSAFE,
             QEMU_CAPS_KVM,
             QEMU_CAPS_DRIVE_FORMAT,
             QEMU_CAPS_DRIVE_SERIAL,
@@ -460,6 +462,7 @@ mymain(void)
             QEMU_CAPS_MIGRATE_QEMU_TCP,
             QEMU_CAPS_MIGRATE_QEMU_EXEC,
             QEMU_CAPS_DRIVE_CACHE_V2,
+            QEMU_CAPS_DRIVE_CACHE_UNSAFE,
             QEMU_CAPS_KVM,
             QEMU_CAPS_DRIVE_FORMAT,
             QEMU_CAPS_DRIVE_SERIAL,
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-disk-drive-cache-unsafe.args b/tests/qemuxml2argvdata/qemuxml2argv-disk-drive-cache-unsafe.args
new file mode 100644
index 0000000..f8ddcd8
--- /dev/null
+++ b/tests/qemuxml2argvdata/qemuxml2argv-disk-drive-cache-unsafe.args
@@ -0,0 +1,5 @@
+LC_ALL=C PATH=/bin HOME=/home/test USER=test LOGNAME=test /usr/bin/qemu -S -M \
+pc -m 214 -smp 1 -nographic -monitor unix:/tmp/test-monitor,server,nowait \
+-no-acpi -boot c -drive file=/dev/HostVG/QEMUGuest1,if=ide,bus=0,unit=0,\
+format=qcow2,cache=unsafe -drive file=/dev/HostVG/QEMUGuest2,if=ide,\
+media=cdrom,bus=1,unit=0,format=raw -net none -serial none -parallel none -usb
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-disk-drive-cache-unsafe.xml b/tests/qemuxml2argvdata/qemuxml2argv-disk-drive-cache-unsafe.xml
new file mode 100644
index 0000000..37185f6
--- /dev/null
+++ b/tests/qemuxml2argvdata/qemuxml2argv-disk-drive-cache-unsafe.xml
@@ -0,0 +1,33 @@
+<domain type='qemu'>
+  <name>QEMUGuest1</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory>219136</memory>
+  <currentMemory>219136</currentMemory>
+  <vcpu>1</vcpu>
+  <os>
+    <type arch='i686' 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</emulator>
+    <disk type='block' device='disk'>
+      <driver name='qemu' type='qcow2' cache='unsafe'/>
+      <source dev='/dev/HostVG/QEMUGuest1'/>
+      <target dev='hda' bus='ide'/>
+      <address type='drive' controller='0' bus='0' unit='0'/>
+    </disk>
+    <disk type='block' device='cdrom'>
+      <driver name='qemu' type='raw'/>
+      <source dev='/dev/HostVG/QEMUGuest2'/>
+      <target dev='hdc' bus='ide'/>
+      <readonly/>
+      <address type='drive' controller='0' bus='1' unit='0'/>
+    </disk>
+    <controller type='ide' index='0'/>
+    <memballoon model='virtio'/>
+  </devices>
+</domain>
diff --git a/tests/qemuxml2argvtest.c b/tests/qemuxml2argvtest.c
index 1dc6a01..9e174b3 100644
--- a/tests/qemuxml2argvtest.c
+++ b/tests/qemuxml2argvtest.c
@@ -341,6 +341,9 @@ mymain(void)
     DO_TEST("disk-drive-cache-directsync", false,
             QEMU_CAPS_DRIVE, QEMU_CAPS_DRIVE_CACHE_V2,
             QEMU_CAPS_DRIVE_CACHE_DIRECTSYNC, QEMU_CAPS_DRIVE_FORMAT);
+    DO_TEST("disk-drive-cache-unsafe", false,
+            QEMU_CAPS_DRIVE, QEMU_CAPS_DRIVE_CACHE_V2,
+            QEMU_CAPS_DRIVE_CACHE_UNSAFE, QEMU_CAPS_DRIVE_FORMAT);
     DO_TEST("disk-drive-network-nbd", false,
             QEMU_CAPS_DRIVE, QEMU_CAPS_DRIVE_FORMAT);
     DO_TEST("disk-drive-network-rbd", false,
diff --git a/tools/virsh.pod b/tools/virsh.pod
index 88dee26..463bee7 100644
--- a/tools/virsh.pod
+++ b/tools/virsh.pod
@@ -1192,8 +1192,8 @@ floppy device; consider using B<update-device> for this usage instead.
 I<mode> can specify the two specific mode I<readonly> or I<shareable>.
 I<persistent> indicates the changes will affect the next boot of the domain.
 I<sourcetype> can indicate the type of source (block|file)
-I<cache> can be one of "default", "none", "writethrough", "writeback", or
-"directsync".
+I<cache> can be one of "default", "none", "writethrough", "writeback",
+"directsync" or "unsafe".
 I<serial> is the serial of disk device. I<shareable> indicates the disk device
 is shareable between domains.
 I<address> is the address of disk device in the form of pci:domain.bus.slot.function,
-- 
1.7.6.2


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