[libvirt] [PATCH] qemu: Warn when using vhost-user without shared memory

[Martin Kletzander]

On Tue, Dec 08, 2015 at 11:35:50AM -0500, John Ferlan wrote:
>
>
>On 12/08/2015 10:24 AM, Martin Kletzander wrote:
>> When user configures vhost-user interface and forgets to also configure
>> any shared memory, the search for the root cause of non-operational
>> interface might take unpleasantly long time.  Let's enhance user
>> experience by emitting a warning in the logs.
>>
>> Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1266982
>>
>> Signed-off-by: Martin Kletzander <mkletzan at redhat.com>
>> ---
>>  src/qemu/qemu_process.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 44 insertions(+)
>>
>> diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
>> index 420196264685..fb471342e790 100644
>> --- a/src/qemu/qemu_process.c
>> +++ b/src/qemu/qemu_process.c
>> @@ -4542,6 +4542,7 @@ qemuProcessLaunch(virConnectPtr conn,
>>      unsigned int hostdev_flags = 0;
>>      size_t nnicindexes = 0;
>>      int *nicindexes = NULL;
>> +    bool check_shmem = false;
>>
>>      VIR_DEBUG("vm=%p name=%s id=%d asyncJob=%d "
>>                "incoming.launchURI=%s incoming.deferredURI=%s "
>> @@ -4749,6 +4750,49 @@ qemuProcessLaunch(virConnectPtr conn,
>>              goto cleanup;
>>      }
>>
>> +    VIR_DEBUG("Checking for any possible (non-fatal) issues");
>> +
>> +    /*
>> +     * For vhost-user to work, the domain has to have some type of
>> +     * shared memory configured.  We're not the proper once to judge
>
>Another typo perhaps?
>
>s/once/ones
>

Oh, what's happening with me again.  Thanks for that, I'll fix all of
them.

>
>> +     * whether shared hugepages or shm are enough and will be in the
>> +     * future, so we'll just warn in case there is none of that
>
>s/there is none of that configured/neither is configured
>
>??

I wans't sure that's grammatically correct, but I wanted to spell it out
just like that.

>
>Current sentance just read strangely.
>

I immediatelly feel better after this "sentance" ;)

>> +     * configured.  Moreover failing would give the false illusion
>> +     * that libvirt is really checking that everything works before
>> +     * running the domain and not only we are unable to do that, but
>> +     * it's also not our aim to do so.
>> +     */
>> +    for (i = 0; i < vm->def->nnets; i++) {
>> +        if (virDomainNetGetActualType(vm->def->nets[i]) ==
>> +                                      VIR_DOMAIN_NET_TYPE_VHOSTUSER) {
>> +            check_shmem = true;
>> +            break;
>> +        }
>> +    }
>> +
>> +    if (check_shmem) {
>> +        bool shmem = vm->def->nshmems;
>> +
>> +        /*
>> +         * This check is by no means complete.  We merely check
>> +         * whetere there are *some* hugepages enabled and *some* NUMA
>> +         * nodes with shared memory access.
>> +         */
>> +        if (!shmem && vm->def->mem.nhugepages) {
>> +            for (i = 0; i < virDomainNumaGetNodeCount(vm->def->numa); i++) {
>> +                if (virDomainNumaGetNodeMemoryAccessMode(vm->def->numa, i) ==
>> +                    VIR_NUMA_MEM_ACCESS_SHARED)
>> +                    shmem = true;
>> +                break;
>> +            }
>> +        }
>> +
>> +        if (!shmem) {
>> +            VIR_WARN("Detected vhost-user interface without any shared memory. "
>> +                     "The interface might not be operational");
>
>You did add a period to the end of the first sentance, but not the second...
>

And even better now =)

>> +        }
>> +    }
>> +
>>      VIR_DEBUG("Building emulator command line");
>>      if (!(cmd = qemuBuildCommandLine(conn, driver, vm->def, priv->monConfig,
>>                                       priv->monJSON, priv->qemuCaps,
>>
>
>--
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