Patchwork [v2] kvm: Check if smp_cpus exceeds max cpus supported by kvm

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Submitter dunrong huang
Date July 31, 2012, 10:14 a.m.
Message ID <1343729663-20527-1-git-send-email-riegamaths@gmail.com>
Download mbox | patch
Permalink /patch/174193/
State New
Headers show

Comments

dunrong huang - July 31, 2012, 10:14 a.m.
From: Dunrong Huang <riegamaths@gmail.com>

Add a helper function for fetching max cpus supported by kvm.

Make QEMU exit with an error message if smp_cpus exceeds limit
of VCPU count retrieved by invoking this helper function.

Signed-off-by: Dunrong Huang <riegamaths@gmail.com>
---
v1 -> v2:
   * Fix indentation
 kvm-all.c |   25 +++++++++++++++++++++++++
 1 files changed, 25 insertions(+), 0 deletions(-)
Peter Maydell - July 31, 2012, 10:20 a.m.
On 31 July 2012 11:14,  <riegamaths@gmail.com> wrote:
>
> @@ -1256,6 +1274,13 @@ int kvm_init(void)
>          goto err;
>      }
>
> +    max_vcpus = kvm_max_vcpus(s);
> +    if (smp_cpus > max_vcpus) {
> +        fprintf(stderr, "Number of SMP cpus requested (%d) exceeds max cpus "
> +                "supported by KVM (%d)\n", smp_cpus, max_vcpus);
> +        exit(1);

Don't exit here, just use 'goto err' like all the other checks in
this function. The caller will handle this and exit (or downgrade
to TCG if the user wanted that).

-- PMM
dunrong huang - July 31, 2012, 10:30 a.m.
2012/7/31 Peter Maydell <peter.maydell@linaro.org>:
> On 31 July 2012 11:14,  <riegamaths@gmail.com> wrote:
>>
>> @@ -1256,6 +1274,13 @@ int kvm_init(void)
>>          goto err;
>>      }
>>
>> +    max_vcpus = kvm_max_vcpus(s);
>> +    if (smp_cpus > max_vcpus) {
>> +        fprintf(stderr, "Number of SMP cpus requested (%d) exceeds max cpus "
>> +                "supported by KVM (%d)\n", smp_cpus, max_vcpus);
>> +        exit(1);
>
> Don't exit here, just use 'goto err' like all the other checks in
> this function. The caller will handle this and exit (or downgrade
> to TCG if the user wanted that).
>
Thanks for your review.
I agree with you, I should use "goto err" like other checks.
> -- PMM

Patch

diff --git a/kvm-all.c b/kvm-all.c
index 2148b20..d1f7d72 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -1207,6 +1207,23 @@  static int kvm_irqchip_create(KVMState *s)
     return 0;
 }
 
+static int kvm_max_vcpus(KVMState *s)
+{
+    int max_vcpus = 4;
+    int ret;
+    ret = kvm_check_extension(s, KVM_CAP_MAX_VCPUS);
+    if (ret) {
+        max_vcpus = ret;
+    } else {
+        ret = kvm_check_extension(s, KVM_CAP_NR_VCPUS);
+        if (ret) {
+            max_vcpus = ret;
+        }
+    }
+
+    return max_vcpus;
+}
+
 int kvm_init(void)
 {
     static const char upgrade_note[] =
@@ -1216,6 +1233,7 @@  int kvm_init(void)
     const KVMCapabilityInfo *missing_cap;
     int ret;
     int i;
+    int max_vcpus;
 
     s = g_malloc0(sizeof(KVMState));
 
@@ -1256,6 +1274,13 @@  int kvm_init(void)
         goto err;
     }
 
+    max_vcpus = kvm_max_vcpus(s);
+    if (smp_cpus > max_vcpus) {
+        fprintf(stderr, "Number of SMP cpus requested (%d) exceeds max cpus "
+                "supported by KVM (%d)\n", smp_cpus, max_vcpus);
+        exit(1);
+    }
+
     s->vmfd = kvm_ioctl(s, KVM_CREATE_VM, 0);
     if (s->vmfd < 0) {
 #ifdef TARGET_S390X