[PATCH v1 1/1] qemu_domain, qemu_process: maxCpus check to non-x86 guests

[Daniel Henrique Barboza <danielhb413@xxxxxxxxx>]

This patch makes two quality of life changes for non-x86 guests. The
first one is a maxCpus validation at qemuDomainDefValidate. The check
is made by the same function used to do that at qemuProcessStartValidateXML,
qemuValidateCpuCount. This ensures that the user doesn't goes over the
board with the maxCpus value when editing the XML, only to be faced with a
runtime error when starting it.

To do that, the following changes were made:

- qemuValidateCpuCount was made public. It was renamed to
qemuProcessValidateCpuCount to be compliant with the other public methods
at qemu_process.h;

- the method signature was slightly adapted to fit the const 'def'
variable used in qemuDomainDefValidate. This change has no downside in
in its original usage at qemuProcessStartValidateXML.

The second QoL change is adding the maxCpus value in the error message
of the now qemuProcessValidateCpuCount. This simple change allows the
user to quickly edit the XML to comply with the acceptable limit without
having to know QEMU internals. x86 guests, that might have been created
prior to the x86 qemuDomainDefValidate maxCpus check code, will also
benefit from this change.

After this patch, this is the expect result running a Power 9 guest with
a maxCpus of 40000:

$ ./virsh start dhb
error: Failed to start domain dhb
error: unsupported configuration: Maximum CPUs greater than specified machine type limit 240

And this is the result when trying to edit maxCpus to an invalid value:

$ ./virsh edit dhb
error: unsupported configuration: Maximum CPUs greater than specified machine type limit 240
Failed. Try again? [y,n,i,f,?]:
error: unsupported configuration: Maximum CPUs greater than specified machine type limit 240

Signed-off-by: Daniel Henrique Barboza <danielhb413@xxxxxxxxx>
---
 src/qemu/qemu_domain.c  |  5 +++++
 src/qemu/qemu_process.c | 13 +++++++------
 src/qemu/qemu_process.h |  3 +++
 3 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index 939b2a3da2..5a39b11da7 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -4100,6 +4100,11 @@ qemuDomainDefValidate(const virDomainDef *def,
         }
     }
 
+    if (!ARCH_IS_X86(def->os.arch) &&
+        qemuProcessValidateCpuCount(def, qemuCaps) < 0) {
+        goto cleanup;
+    }
+
     if (def->nresctrls &&
         def->virtType != VIR_DOMAIN_VIRT_KVM) {
         virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
index 29b0ba1590..0de5b503d6 100644
--- a/src/qemu/qemu_process.c
+++ b/src/qemu/qemu_process.c
@@ -3901,9 +3901,9 @@ qemuProcessSPICEAllocatePorts(virQEMUDriverPtr driver,
 }
 
 
-static int
-qemuValidateCpuCount(virDomainDefPtr def,
-                     virQEMUCapsPtr qemuCaps)
+int
+qemuProcessValidateCpuCount(const virDomainDef *def,
+                            virQEMUCapsPtr qemuCaps)
 {
     unsigned int maxCpus = virQEMUCapsGetMachineMaxCpus(qemuCaps, def->os.machine);
 
@@ -3914,8 +3914,9 @@ qemuValidateCpuCount(virDomainDefPtr def,
     }
 
     if (maxCpus > 0 && virDomainDefGetVcpusMax(def) > maxCpus) {
-        virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
-                       _("Maximum CPUs greater than specified machine type limit"));
+        virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                       _("Maximum CPUs greater than specified machine type limit %u"),
+                       maxCpus);
         return -1;
     }
 
@@ -5165,7 +5166,7 @@ qemuProcessStartValidateXML(virQEMUDriverPtr driver,
      * If back compat isn't a concern, XML validation should probably
      * be done at parse time.
      */
-    if (qemuValidateCpuCount(vm->def, qemuCaps) < 0)
+    if (qemuProcessValidateCpuCount(vm->def, qemuCaps) < 0)
         return -1;
 
     /* checks below should not be executed when starting a qemu process for a
diff --git a/src/qemu/qemu_process.h b/src/qemu/qemu_process.h
index c2f7c2b5d2..1716230475 100644
--- a/src/qemu/qemu_process.h
+++ b/src/qemu/qemu_process.h
@@ -215,4 +215,7 @@ int qemuProcessStartManagedPRDaemon(virDomainObjPtr vm);
 
 void qemuProcessKillManagedPRDaemon(virDomainObjPtr vm);
 
+int qemuProcessValidateCpuCount(const virDomainDef *def,
+                                virQEMUCapsPtr qemuCaps);
+
 #endif /* __QEMU_PROCESS_H__ */
-- 
2.17.1

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