Re: [PATCH] kvm tools: Default guest cpu count to host cpu count

[Cyrill Gorcunov <gorcunov@gmail.com>]

On 05/19/2011 11:04 PM, David Ahern wrote:
> 
> On 05/18/11 13:56, Sasha Levin wrote:
>> If user haven't specified cpu count for the guest, use
>> the amount of online cpus on the host.
>>
>> Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
>> ---
>>  tools/kvm/kvm-run.c |    9 ++++++---
>>  1 files changed, 6 insertions(+), 3 deletions(-)
>>
>> diff --git a/tools/kvm/kvm-run.c b/tools/kvm/kvm-run.c
>> index 63181bf..1517264 100644
>> --- a/tools/kvm/kvm-run.c
>> +++ b/tools/kvm/kvm-run.c
>> @@ -70,7 +70,7 @@ extern int  active_console;
>>  
>>  bool do_debug_print = false;
>>  
>> -static int nrcpus = 1;
>> +static int nrcpus;
>>  
>>  static const char * const run_usage[] = {
>>  	"kvm run [<options>] [<kernel image>]",
>> @@ -409,6 +409,8 @@ int kvm_cmd_run(int argc, const char **argv, const char *prefix)
>>  	signal(SIGQUIT, handle_sigquit);
>>  	signal(SIGUSR1, handle_sigusr1);
>>  
>> +	nr_online_cpus = sysconf(_SC_NPROCESSORS_ONLN);
>> +
>>  	while (argc != 0) {
>>  		argc = parse_options(argc, argv, options, run_usage,
>>  				PARSE_OPT_STOP_AT_NON_OPTION);
>> @@ -439,7 +441,9 @@ int kvm_cmd_run(int argc, const char **argv, const char *prefix)
>>  
>>  	vmlinux_filename = find_vmlinux();
>>  
>> -	if (nrcpus < 1 || nrcpus > KVM_NR_CPUS)
>> +	if (nrcpus == 0)
>> +		nrcpus = nr_online_cpus;
>> +	else if (nrcpus < 1 || nrcpus > KVM_NR_CPUS)
>>  		die("Number of CPUs %d is out of [1;%d] range", nrcpus, KVM_NR_CPUS);
> 
> What prevents nr_online_cpus from being greater than KVM_NR_CPUS? Since
> that latter is a #define, might want to change 'else if' to if there.
> 
> David
> 

Good catch! We should add a constraint here and limit it to KVM_NR_CPUS.

-- 
            Cyrill