On Wed, 14 May 2014 16:18:42 -0300
Eduardo Habkost <ehabk...@redhat.com> wrote:
> If a given machine have max_cpus set, not just smp_cpus needs to be
> limited, but the total number of CPUs (considering CPU hotplug) for the
> machine.
>
> We also had yet another max_cpus limit check at smp_parse(), ensuring
> that max_cpus < MAX_CPUMASK_BITS.
>
> This patch unifies the machine->max_cpus and MAX_CPUMASK_BITS checks,
> and also moves the (smp_cpus <= max_cpus) outside smp_parse(), to keep
> all checks in the same place.
>
> With those changes, the new code ensures that:
>
> 1 <= smp_cpus <= max_cpus <= machine->max_cpus <= MAX_CPUMASK_BITS
>
> Signed-off-by: Eduardo Habkost <ehabk...@redhat.com>
> Cc: Peter Maydell <peter.mayd...@linaro.org>
> Cc: Andreas Färber <afaer...@suse.de>
> Cc: Igor Mammedov <imamm...@redhat.com>
> Cc: Marcelo Tosatti <mtosa...@redhat.com>
> ---
> Changes v1 -> v2:
> * v1 was: [PATCH] vl.c: Check max_cpus limit instead of smp_cpus
> * Unify machine->max_cpus and MAX_CPUMASK_BITS check
> * Move all checks outside smp_parse()
> * Add assert() lines ensuring the results are consistent
> * s/machine/machine_class/, after rebase to latest qemu.git
> (commit 6b342cc)
> ---
> vl.c | 26 ++++++++++++++------------
> 1 file changed, 14 insertions(+), 12 deletions(-)
>
> diff --git a/vl.c b/vl.c
> index 709d8cd..749abbd 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -1425,15 +1425,6 @@ static void smp_parse(QemuOpts *opts)
> max_cpus = smp_cpus;
> }
>
> - if (max_cpus > MAX_CPUMASK_BITS) {
> - fprintf(stderr, "Unsupported number of maxcpus\n");
> - exit(1);
> - }
> - if (max_cpus < smp_cpus) {
> - fprintf(stderr, "maxcpus must be equal to or greater than smp\n");
> - exit(1);
> - }
> -
> }
>
> static void configure_realtime(QemuOpts *opts)
> @@ -4054,13 +4045,24 @@ int main(int argc, char **argv, char **envp)
> smp_parse(qemu_opts_find(qemu_find_opts("smp-opts"), NULL));
>
> machine_class->max_cpus = machine_class->max_cpus ?: 1; /* Default to UP
> */
> - if (smp_cpus > machine_class->max_cpus) {
> - fprintf(stderr, "Number of SMP cpus requested (%d), exceeds max cpus
> "
> - "supported by machine `%s' (%d)\n", smp_cpus,
> + machine_class->max_cpus = MIN(machine_class->max_cpus, MAX_CPUMASK_BITS);
> +
> + if (max_cpus < smp_cpus) {
> + fprintf(stderr, "maxcpus must be equal to or greater than smp\n");
> + exit(1);
> + }
> + if (max_cpus > machine_class->max_cpus) {
> + fprintf(stderr, "Total number of CPUs (%d), exceeds maximum "
> + "supported by machine `%s' (%d)\n", max_cpus,
> machine_class->name, machine_class->max_cpus);
> exit(1);
> }
>
> + assert(1 <= smp_cpus);
> + assert(smp_cpus <= max_cpus);
> + assert(max_cpus <= machine_class->max_cpus);
> + assert(machine_class->max_cpus <= MAX_CPUMASK_BITS);
It would be better complement some assertions with checks with proper error
reporting.
also try to test following combos:
-smp 0,maxcpus=0
-smp -1
-smp 0,maxcpus=-1
-smp 1,maxcpus=0xFFFFFFFF
we need to handle values as unsigned at least and maybe also ban 0 as valid
one.
The rest seems to work as expected.
> +
> /*
> * Get the default machine options from the machine if it is not already
> * specified either by the configuration file or by the command line.
> --
> 1.9.0
>
--
Regards,
Igor
