From e7f6fc0ea19e73e1ecd9a54f12ac9f2df7cb30cf Mon Sep 17 00:00:00 2001

Message-Id: <e7f6fc0ea19e73e1ecd9a54f12ac9f2df7cb30cf@dist-git>

From: Jiri Denemark <jdenemar@redhat.com>

Date: Fri, 6 Oct 2017 14:49:07 +0200

Subject: [PATCH] qemu: Fix CPU model broken by older libvirt

When libvirt older than 3.9.0 reconnected to a running domain started by

old libvirt it could have messed up the expansion of host-model by

adding features QEMU does not support (such as cmt). Thus whenever we

reconnect to a running domain, revert to an active snapshot, or restore

a saved domain we need to check the guest CPU model and remove the

CPU features unknown to QEMU. We can do this because we know the domain

was successfully started, which means the CPU did not contain the

features when libvirt started the domain.

https://bugzilla.redhat.com/show_bug.cgi?id=1495171

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>

Reviewed-by: Pavel Hrdina <phrdina@redhat.com>

(cherry picked from commit 6a6f6b91e0e76480ea961f83135efcb4faf3284a)

Conflicts:

	src/qemu/qemu_domain.c,

	src/qemu/qemu_domain.h -- context, one more function new

            function upstream

https://bugzilla.redhat.com/show_bug.cgi?id=1508549

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>

---

 src/qemu/qemu_domain.c  | 75 +++++++++++++++++++++++++++++++++++++++++++++++++

 src/qemu/qemu_domain.h  |  4 +++

 src/qemu/qemu_driver.c  | 14 +++++++++

 src/qemu/qemu_process.c |  9 ++++++

 4 files changed, 102 insertions(+)

diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c

index a41657099f..68c1f3b7c5 100644

--- a/src/qemu/qemu_domain.c

+++ b/src/qemu/qemu_domain.c

@@ -9324,3 +9324,78 @@ qemuDomainUpdateCPU(virDomainObjPtr vm,

     return 0;

 }

+

+

+/**

+ * qemuDomainFixupCPUS:

+ * @vm: domain object

+ * @origCPU: original CPU used when the domain was started

+ *

+ * Libvirt older than 3.9.0 could have messed up the expansion of host-model

+ * CPU when reconnecting to a running domain by adding features QEMU does not

+ * support (such as cmt). This API fixes both the actual CPU provided by QEMU

+ * (stored in the domain object) and the @origCPU used when starting the

+ * domain.

+ *

+ * This is safe even if the original CPU definition used mode='custom' (rather

+ * than host-model) since we know QEMU was able to start the domain and thus

+ * the CPU definitions do not contain any features unknown to QEMU.

+ *

+ * This function can only be used on an active domain or when restoring a

+ * domain which was running.

+ *

+ * Returns 0 on success, -1 on error.

+ */

+int

+qemuDomainFixupCPUs(virDomainObjPtr vm,

+                    virCPUDefPtr *origCPU)

+{

+    virCPUDefPtr fixedCPU = NULL;

+    virCPUDefPtr fixedOrig = NULL;

+    virArch arch = vm->def->os.arch;

+    int ret = 0;

+

+    if (!ARCH_IS_X86(arch))

+        return 0;

+

+    if (!vm->def->cpu ||

+        vm->def->cpu->mode != VIR_CPU_MODE_CUSTOM ||

+        !vm->def->cpu->model)

+        return 0;

+

+    /* Missing origCPU means QEMU created exactly the same virtual CPU which

+     * we asked for or libvirt was too old to mess up the translation from

+     * host-model.

+     */

+    if (!*origCPU)

+        return 0;

+

+    if (virCPUDefFindFeature(vm->def->cpu, "cmt") &&

+        (!(fixedCPU = virCPUDefCopyWithoutModel(vm->def->cpu)) ||

+         virCPUDefCopyModelFilter(fixedCPU, vm->def->cpu, false,

+                                  virQEMUCapsCPUFilterFeatures, &arch) < 0))

+        goto cleanup;

+

+    if (virCPUDefFindFeature(*origCPU, "cmt") &&

+        (!(fixedOrig = virCPUDefCopyWithoutModel(*origCPU)) ||

+         virCPUDefCopyModelFilter(fixedOrig, *origCPU, false,

+                                  virQEMUCapsCPUFilterFeatures, &arch) < 0))

+        goto cleanup;

+

+    if (fixedCPU) {

+        virCPUDefFree(vm->def->cpu);

+        VIR_STEAL_PTR(vm->def->cpu, fixedCPU);

+    }

+

+    if (fixedOrig) {

+        virCPUDefFree(*origCPU);

+        VIR_STEAL_PTR(*origCPU, fixedOrig);

+    }

+

+    ret = 0;

+

+ cleanup:

+    virCPUDefFree(fixedCPU);

+    virCPUDefFree(fixedOrig);

+    return ret;

+}

diff --git a/src/qemu/qemu_domain.h b/src/qemu/qemu_domain.h

index 7ad34e563e..1a658bcf7e 100644

--- a/src/qemu/qemu_domain.h

+++ b/src/qemu/qemu_domain.h

@@ -930,4 +930,8 @@ qemuDomainUpdateCPU(virDomainObjPtr vm,

                     virCPUDefPtr cpu,

                     virCPUDefPtr *origCPU);

+int

+qemuDomainFixupCPUs(virDomainObjPtr vm,

+                    virCPUDefPtr *origCPU);

+

 #endif /* __QEMU_DOMAIN_H__ */

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c

index b6d72303ca..bfd7ff6c09 100644

--- a/src/qemu/qemu_driver.c

+++ b/src/qemu/qemu_driver.c

@@ -6500,6 +6500,13 @@ qemuDomainSaveImageStartVM(virConnectPtr conn,

         }

     }

+    /* No cookie means libvirt which saved the domain was too old to mess up

+     * the CPU definitions.

+     */

+    if (cookie &&

+        qemuDomainFixupCPUs(vm, &cookie->cpu) < 0)

+        goto cleanup;

+

     if (qemuProcessStart(conn, driver, vm, cookie ? cookie->cpu : NULL,

                          asyncJob, "stdio", *fd, path, NULL,

                          VIR_NETDEV_VPORT_PROFILE_OP_RESTORE,

@@ -15520,6 +15527,13 @@ qemuDomainRevertToSnapshot(virDomainSnapshotPtr snapshot,

             if (config)

                 virDomainObjAssignDef(vm, config, false, NULL);

+            /* No cookie means libvirt which saved the domain was too old to

+             * mess up the CPU definitions.

+             */

+            if (cookie &&

+                qemuDomainFixupCPUs(vm, &cookie->cpu) < 0)

+                goto cleanup;

+

             rc = qemuProcessStart(snapshot->domain->conn, driver, vm,

                                   cookie ? cookie->cpu : NULL,

                                   QEMU_ASYNC_JOB_START, NULL, -1, NULL, snap,

diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c

index 0bed084381..5802a553cf 100644

--- a/src/qemu/qemu_process.c

+++ b/src/qemu/qemu_process.c

@@ -6667,6 +6667,7 @@ qemuProcessRefreshCPU(virQEMUDriverPtr driver,

                       virDomainObjPtr vm)

 {

     virCapsPtr caps = virQEMUDriverGetCapabilities(driver, false);

+    qemuDomainObjPrivatePtr priv = vm->privateData;

     virCPUDefPtr host = NULL;

     virCPUDefPtr cpu = NULL;

     int ret = -1;

@@ -6701,6 +6702,14 @@ qemuProcessRefreshCPU(virQEMUDriverPtr driver,

         if (qemuProcessUpdateCPU(driver, vm, QEMU_ASYNC_JOB_NONE) < 0)

             goto cleanup;

+    } else if (!virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_QUERY_CPU_MODEL_EXPANSION)) {

+        /* We only try to fix CPUs when the libvirt/QEMU combo used to start

+         * the domain did not know about query-cpu-model-expansion in which

+         * case the host-model is known to not contain features which QEMU

+         * doesn't know about.

+         */

+        if (qemuDomainFixupCPUs(vm, &priv->origCPU) < 0)

+            goto cleanup;

     }

     ret = 0;

-- 

2.15.0