[PATCH] Bail out when VCPU_CREATE fails

[PATCH] Bail out when VCPU_CREATE fails

[Alexander Graf]

When we fail to create a VCPU we have no way to tell our callers that something
failed. So the caller happily uses a completely broken state.

This code should become deprecated in the process of converting qemu-kvm to
qemu anyways, so let's not care about remdeling it but just bailing out when
something breaks. Also give the user a hint on why the VCPU_CREATE might have
failed.

This fixes a segmentation fault with -smp > VCPU_MAX in the host kernel.

Signed-off-by: Alexander Graf <agraf@suse.de>
Reported-by: Michael Tokarev <mjt@tls.msk.ru>

---

Please also commit this to the -stable branch.
---
 qemu-kvm.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/qemu-kvm.c b/qemu-kvm.c
index 7772434..4d19c80 100644
--- a/qemu-kvm.c
+++ b/qemu-kvm.c
@@ -448,7 +448,8 @@ static void kvm_create_vcpu(CPUState *env, int id)
     r = kvm_vm_ioctl(kvm_state, KVM_CREATE_VCPU, id);
     if (r < 0) {
         fprintf(stderr, "kvm_create_vcpu: %m\n");
-        return;
+        fprintf(stderr, "Failed to create vCPU. Check the -smp parameter.\n");
+        goto err;
     }
 
     env->kvm_fd = r;
@@ -476,6 +477,9 @@ static void kvm_create_vcpu(CPUState *env, int id)
     return;
   err_fd:
     close(env->kvm_fd);
+  err:
+    /* We're no good with semi-broken states. */
+    abort();
 }
 
 static int kvm_set_boot_vcpu_id(kvm_context_t kvm, uint32_t id)
-- 
1.6.0.2

Re: [PATCH] Bail out when VCPU_CREATE fails

[Avi Kivity]

On 03/22/2010 12:49 PM, Alexander Graf wrote:
> When we fail to create a VCPU we have no way to tell our callers that something
> failed. So the caller happily uses a completely broken state.
>
> This code should become deprecated in the process of converting qemu-kvm to
> qemu anyways, so let's not care about remdeling it but just bailing out when
> something breaks. Also give the user a hint on why the VCPU_CREATE might have
> failed.
>
> This fixes a segmentation fault with -smp>  VCPU_MAX in the host kernel.
>
>    

Applied, thanks.  Note, kvm reports the number of supported vcpus using 
KVM_CAP_NR_VCPUS, so we can fail in vl.c.

-- 
error compiling committee.c: too many arguments to function

Re: [PATCH] Bail out when VCPU_CREATE fails

[Alexander Graf]

On 24.03.2010, at 10:32, Avi Kivity wrote:

> On 03/22/2010 12:49 PM, Alexander Graf wrote:
>> When we fail to create a VCPU we have no way to tell our callers that something
>> failed. So the caller happily uses a completely broken state.
>> 
>> This code should become deprecated in the process of converting qemu-kvm to
>> qemu anyways, so let's not care about remdeling it but just bailing out when
>> something breaks. Also give the user a hint on why the VCPU_CREATE might have
>> failed.
>> 
>> This fixes a segmentation fault with -smp>  VCPU_MAX in the host kernel.
>> 
>>   
> 
> Applied, thanks.  Note, kvm reports the number of supported vcpus using KVM_CAP_NR_VCPUS, so we can fail in vl.c.

Sounds like the right fix to do for qemu.git. As soon as SMP support is in there.


Alex