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Re: [libvirt] [PATCH v3 2/2] qemu: Add support to QXL's max_outputs parameter



On Fri, Mar 25, 2016 at 10:58:13AM +0100, Christophe Fergeau wrote:
Hey,

On Thu, Mar 24, 2016 at 05:01:52PM +0100, Martin Kletzander wrote:
Historically, we added heads=1 to videos, but for example for qxl, we
did not reflect that on the command line.  Implementing that now could
mean that if user were to migrate from older to newer libvirt, the
command-line for qemu would differ.  In order for that not to happen a
migration cookie flag is introduced.

Signed-off-by: Martin Kletzander <mkletzan redhat com>
---
 src/qemu/qemu_command.c                            |  8 +++
 src/qemu/qemu_migration.c                          | 64 ++++++++++++++++++++--
 .../qemuxml2argv-video-qxl-heads.args              | 28 ++++++++++
 .../qemuxml2argv-video-qxl-heads.xml               | 47 ++++++++++++++++
 tests/qemuxml2argvtest.c                           |  8 +++
 .../qemuxml2xmlout-video-qxl-heads.xml             | 47 ++++++++++++++++
 tests/qemuxml2xmltest.c                            |  2 +
 7 files changed, 198 insertions(+), 6 deletions(-)
 create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-video-qxl-heads.args
 create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-video-qxl-heads.xml
 create mode 100644 tests/qemuxml2xmloutdata/qemuxml2xmlout-video-qxl-heads.xml

diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index 0331789b6b59..f6b102e96bb2 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -3985,6 +3985,14 @@ qemuBuildDeviceVideoStr(const virDomainDef *def,
             /* QEMU accepts mebibytes for vgamem_mb. */
             virBufferAsprintf(&buf, ",vgamem_mb=%u", video->vgamem / 1024);
         }
+
+        if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_QXL_VGA_MAX_OUTPUTS) &&
+            virQEMUCapsGet(qemuCaps, QEMU_CAPS_QXL_MAX_OUTPUTS)) {

This test could be more similar to the one for vgamem/vram64
above for consistency, and be
       if ((video->primary && virQEMUCapsGet(qemuCaps, QEMU_CAPS_QXL_VGA_MAX_OUTPUTS)) ||
           (!video->primary && virQEMUCapsGet(qemuCaps, QEMU_CAPS_QXL_MAX_OUTPUTS))) {
       }

Since both caps will always be set/not set, this is not going to make a
difference, and your version is easier to read imo.


well, yes, just in a corner case with "special" qemu.  I'm in favor of
using the parameter for all cards or none, so that's why I went with
this approach.




+            if (video->heads)
+                virBufferAsprintf(&buf, ",max_outputs=%u", video->heads);
+        } else {
+            video->heads = 0;
+        }

Is it typical to modify the domain def content from within
qemu_command.c ?


Not much, we're in the middle of refactoring some of that.  I rebased
this version and it's now in a bit different place.  The trick here is
that we're modifying the live XML, not the one on the disk, so the
definition is not changed on the disk, but if someone calls dumpxml on
the running domain, there will be no heads= parameter to reflect what we
told qemu.

     } else if (video->vram &&
         ((video->type == VIR_DOMAIN_VIDEO_TYPE_VGA &&
           virQEMUCapsGet(qemuCaps, QEMU_CAPS_VGA_VGAMEM)) ||
diff --git a/src/qemu/qemu_migration.c b/src/qemu/qemu_migration.c
index 8bc76bf1671d..f83b6362d228 100644
--- a/src/qemu/qemu_migration.c
+++ b/src/qemu/qemu_migration.c
@@ -87,6 +87,7 @@ enum qemuMigrationCookieFlags {
     QEMU_MIGRATION_COOKIE_FLAG_NBD,
     QEMU_MIGRATION_COOKIE_FLAG_STATS,
     QEMU_MIGRATION_COOKIE_FLAG_MEMORY_HOTPLUG,
+    QEMU_MIGRATION_COOKIE_FLAG_VIDEO_HEADS,

     QEMU_MIGRATION_COOKIE_FLAG_LAST
 };
@@ -100,7 +101,8 @@ VIR_ENUM_IMPL(qemuMigrationCookieFlag,
               "network",
               "nbd",
               "statistics",
-              "memory-hotplug");
+              "memory-hotplug",
+              "video-heads");

 enum qemuMigrationCookieFeatures {
     QEMU_MIGRATION_COOKIE_GRAPHICS  = (1 << QEMU_MIGRATION_COOKIE_FLAG_GRAPHICS),
@@ -110,6 +112,7 @@ enum qemuMigrationCookieFeatures {
     QEMU_MIGRATION_COOKIE_NBD = (1 << QEMU_MIGRATION_COOKIE_FLAG_NBD),
     QEMU_MIGRATION_COOKIE_STATS = (1 << QEMU_MIGRATION_COOKIE_FLAG_STATS),
     QEMU_MIGRATION_COOKIE_MEMORY_HOTPLUG = (1 << QEMU_MIGRATION_COOKIE_FLAG_MEMORY_HOTPLUG),
+    QEMU_MIGRATION_COOKIE_VIDEO_HEADS = (1 << QEMU_MIGRATION_COOKIE_FLAG_VIDEO_HEADS),
 };

 typedef struct _qemuMigrationCookieGraphics qemuMigrationCookieGraphics;
@@ -1386,6 +1389,9 @@ qemuMigrationBakeCookie(qemuMigrationCookiePtr mig,
     if (flags & QEMU_MIGRATION_COOKIE_MEMORY_HOTPLUG)
         mig->flagsMandatory |= QEMU_MIGRATION_COOKIE_MEMORY_HOTPLUG;

+    if (flags & QEMU_MIGRATION_COOKIE_VIDEO_HEADS)
+        mig->flagsMandatory |= QEMU_MIGRATION_COOKIE_VIDEO_HEADS;
+
     if (!(*cookieout = qemuMigrationCookieXMLFormatStr(driver, mig)))
         return -1;

@@ -3091,6 +3097,7 @@ qemuMigrationBeginPhase(virQEMUDriverPtr driver,
     qemuDomainObjPrivatePtr priv = vm->privateData;
     virCapsPtr caps = NULL;
     unsigned int cookieFlags = QEMU_MIGRATION_COOKIE_LOCKSTATE;
+    size_t i = 0, j = 0;

     VIR_DEBUG("driver=%p, vm=%p, xmlin=%s, dname=%s,"
               " cookieout=%p, cookieoutlen=%p,"
@@ -3131,8 +3138,6 @@ qemuMigrationBeginPhase(virQEMUDriverPtr driver,

         if (nmigrate_disks) {
             if (has_drive_mirror) {
-                size_t i, j;
-

Nit: I would keep these variables here, and declare a new size_t i;
variable in the QXL_MAX_OUTPUTS block. Smaller scope to look at when one
wants to look at where/how the 'i' variable is used.


Could be, I'v eno problem with changing that ;)

                 /* Check user requested only known disk targets. */
                 for (i = 0; i < nmigrate_disks; i++) {
                     for (j = 0; j < vm->def->ndisks; j++) {
@@ -3177,6 +3182,27 @@ qemuMigrationBeginPhase(virQEMUDriverPtr driver,
          vm->newDef && virDomainDefHasMemoryHotplug(vm->newDef)))
         cookieFlags |= QEMU_MIGRATION_COOKIE_MEMORY_HOTPLUG;

+    /*
+     * If there is at least one QXL video with number of heads
+     * defined, we need to indicate that we now know how to
+     * properly specify that on the command-line.  Destination
+     * that cannot do this will properly block such migration and
+     * new enough destination will know that the value can be kept
+     * and not reset.
+     */
+    if (virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_QXL_MAX_OUTPUTS) &&
+        virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_QXL_VGA_MAX_OUTPUTS)) {
+        for (i = 0; i < vm->def->nvideos; i++) {
+            virDomainVideoDefPtr vid = vm->def->videos[i];
+
+            if (vid->type == VIR_DOMAIN_VIDEO_TYPE_QXL &&
+                vid->heads) {
+                cookieFlags |= QEMU_MIGRATION_COOKIE_VIDEO_HEADS;
+                break;
+            }
+        }
+    }
+
     if (!(mig = qemuMigrationEatCookie(driver, vm, NULL, 0, 0)))
         goto cleanup;

@@ -3404,6 +3430,32 @@ qemuMigrationPrepareIncoming(virDomainObjPtr vm,
 }

 static int
+qemuMigratePrepareDomain(virConnectPtr dconn,
+                         virQEMUDriverPtr driver,
+                         virDomainObjPtr vm,
+                         qemuMigrationCookiePtr mig)
+{
+    size_t i = 0;
+
+    if (!(mig->flags & QEMU_MIGRATION_COOKIE_VIDEO_HEADS)) {
+        /*
+         * Source didn't know how to properly specify number of heads
+         * for QXL video, so in order to migrate with ABI kept, leave
+         * the value unspecified.
+         */
+        for (i = 0; i < vm->def->nvideos; i++) {
+            virDomainVideoDefPtr vid = vm->def->videos[i];
+
+            if (vid->type == VIR_DOMAIN_VIDEO_TYPE_QXL)
+                vid->heads = 0;
+        }
+    }
+
+    return qemuProcessPrepareDomain(dconn, driver, vm,
+                                    VIR_QEMU_PROCESS_START_AUTODESTROY);
+}
+
+static int
 qemuMigrationPrepareAny(virQEMUDriverPtr driver,
                         virConnectPtr dconn,
                         const char *cookiein,
@@ -3546,7 +3598,8 @@ qemuMigrationPrepareAny(virQEMUDriverPtr driver,
     if (!(mig = qemuMigrationEatCookie(driver, vm, cookiein, cookieinlen,
                                        QEMU_MIGRATION_COOKIE_LOCKSTATE |
                                        QEMU_MIGRATION_COOKIE_NBD |
-                                       QEMU_MIGRATION_COOKIE_MEMORY_HOTPLUG)))
+                                       QEMU_MIGRATION_COOKIE_MEMORY_HOTPLUG |
+                                       QEMU_MIGRATION_COOKIE_VIDEO_HEADS)))
         goto cleanup;

     if (STREQ_NULLABLE(protocol, "rdma") &&
@@ -3590,8 +3643,7 @@ qemuMigrationPrepareAny(virQEMUDriverPtr driver,
         goto stopjob;
     dataFD[0] = -1; /* the FD is now owned by incoming */

-    if (qemuProcessPrepareDomain(dconn, driver, vm,
-                                 VIR_QEMU_PROCESS_START_AUTODESTROY) < 0)
+    if (qemuMigratePrepareDomain(dconn, driver, vm, mig) < 0)
         goto stopjob;

     if (qemuProcessPrepareHost(driver, vm, !!incoming) < 0)
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-video-qxl-heads.args b/tests/qemuxml2argvdata/qemuxml2argv-video-qxl-heads.args
new file mode 100644
index 000000000000..a939177088f9
--- /dev/null
+++ b/tests/qemuxml2argvdata/qemuxml2argv-video-qxl-heads.args
@@ -0,0 +1,28 @@
+LC_ALL=C \
+PATH=/bin \
+HOME=/home/test \
+USER=test \
+LOGNAME=test \
+QEMU_AUDIO_DRV=none \
+/usr/bin/qemu \
+-name QEMUGuest1 \
+-S \
+-M pc \
+-m 214 \
+-smp 1 \
+-uuid c7a5fdbd-edaf-9455-926a-d65c16db1809 \
+-nographic \
+-nodefaults \
+-monitor unix:/tmp/lib/domain--1-QEMUGuest1/monitor.sock,server,nowait \
+-no-acpi \
+-boot c \
+-usb \
+-drive file=/dev/HostVG/QEMUGuest1,format=raw,if=none,id=drive-ide0-0-0 \
+-device ide-drive,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0 \
+-device qxl-vga,id=video0,ram_size=67108864,vram_size=67108864,max_outputs=1,\
+bus=pci.0,addr=0x2 \
+-device qxl,id=video1,ram_size=67108864,vram_size=33554432,max_outputs=3,\
+bus=pci.0,addr=0x4 \
+-device qxl,id=video2,ram_size=67108864,vram_size=67108864,max_outputs=7,\
+bus=pci.0,addr=0x5 \
+-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-video-qxl-heads.xml b/tests/qemuxml2argvdata/qemuxml2argv-video-qxl-heads.xml
new file mode 100644
index 000000000000..45d08745e652
--- /dev/null
+++ b/tests/qemuxml2argvdata/qemuxml2argv-video-qxl-heads.xml
@@ -0,0 +1,47 @@
+<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='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'>
+      <source dev='/dev/HostVG/QEMUGuest1'/>
+      <target dev='hda' bus='ide'/>
+      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
+    </disk>
+    <controller type='usb' index='0'>
+      <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'/>
+    <video>
+      <model type='qxl' ram='65536' vram='32768' vgamem='8192' heads='3'/>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
+    </video>
+    <video>
+      <model type='qxl' ram='65536' vram='65536' vgamem='8192' heads='7'/>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>
+    </video>
+    <video>
+      <model type='qxl' ram='65536' vram='65536' vgamem='8192' heads='1' primary='yes'/>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
+    </video>

Maybe one of the tests could check what happens if heads is not
specified ? (though iirc libvirt always adds it to the XML?)


I thought there were some tests that do that.  Turns out there aren't,
so I'll add another one, thanks for the tip!

Not acking as I'm not familiar with the migration code at all, but

Reviewed-by: Christophe Fergeau <cfergeau redhat com>

Christophe

No problem, I'll repost the rebased version with the nits fixed

Thanks for the review,
Martin

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