Re: [Qemu-devel] [PATCH RFC 2/2] numa: make -numa parser dynamically allocate CPUs masks

[Eduardo Habkost <ehabkost@redhat.com>]

On Wed, Nov 16, 2016 at 05:02:56PM +0100, Igor Mammedov wrote:
> so it won't impose an additional limits on max_cpus limits
> supported by different targets.
> 
> It removes global MAX_CPUMASK_BITS constant and need to
> bump it up whenever max_cpus is being increased for
> a target above MAX_CPUMASK_BITS value.
> 
> Use runtime max_cpus value instead to allocate sufficiently
> sized node_cpu bitmasks in numa parser.
> 
> Signed-off-by: Igor Mammedov <imammedo@redhat.com>
> ---
>  include/sysemu/numa.h   |  2 +-
>  include/sysemu/sysemu.h |  7 -------
>  numa.c                  | 19 ++++++++++++-------
>  vl.c                    |  5 -----
>  4 files changed, 13 insertions(+), 20 deletions(-)
> 
> diff --git a/include/sysemu/numa.h b/include/sysemu/numa.h
> index 4da808a..8f09dcf 100644
> --- a/include/sysemu/numa.h
> +++ b/include/sysemu/numa.h
> @@ -17,7 +17,7 @@ struct numa_addr_range {
>  
>  typedef struct node_info {
>      uint64_t node_mem;
> -    DECLARE_BITMAP(node_cpu, MAX_CPUMASK_BITS);
> +    unsigned long *node_cpu;
>      struct HostMemoryBackend *node_memdev;
>      bool present;
>      QLIST_HEAD(, numa_addr_range) addr; /* List to store address ranges */
> diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
> index 66c6f15..cccde56 100644
> --- a/include/sysemu/sysemu.h
> +++ b/include/sysemu/sysemu.h
> @@ -168,13 +168,6 @@ extern int mem_prealloc;
>  #define MAX_NODES 128
>  #define NUMA_NODE_UNASSIGNED MAX_NODES
>  
> -/* The following shall be true for all CPUs:
> - *   cpu->cpu_index < max_cpus <= MAX_CPUMASK_BITS
> - *
> - * Note that cpu->get_arch_id() may be larger than MAX_CPUMASK_BITS.
> - */
> -#define MAX_CPUMASK_BITS 288
> -

Nice!

>  #define MAX_OPTION_ROMS 16
>  typedef struct QEMUOptionRom {
>      const char *name;
> diff --git a/numa.c b/numa.c
> index 9c09e45..5542e40 100644
> --- a/numa.c
> +++ b/numa.c
> @@ -266,20 +266,20 @@ static char *enumerate_cpus(unsigned long *cpus, int max_cpus)
>  static void validate_numa_cpus(void)
>  {
>      int i;
> -    DECLARE_BITMAP(seen_cpus, MAX_CPUMASK_BITS);
> +    unsigned long *seen_cpus = bitmap_new(max_cpus);
>  
> -    bitmap_zero(seen_cpus, MAX_CPUMASK_BITS);
> +    bitmap_zero(seen_cpus, max_cpus);

bitmap_new() already returns a zeroed bitmap.

>      for (i = 0; i < nb_numa_nodes; i++) {
> -        if (bitmap_intersects(seen_cpus, numa_info[i].node_cpu,
> -                              MAX_CPUMASK_BITS)) {
> +        if (bitmap_intersects(seen_cpus, numa_info[i].node_cpu, max_cpus)) {
>              bitmap_and(seen_cpus, seen_cpus,
> -                       numa_info[i].node_cpu, MAX_CPUMASK_BITS);
> +                       numa_info[i].node_cpu, max_cpus);
>              error_report("CPU(s) present in multiple NUMA nodes: %s",
>                           enumerate_cpus(seen_cpus, max_cpus));
> +            bitmap_free(seen_cpus);
>              exit(EXIT_FAILURE);
>          }
>          bitmap_or(seen_cpus, seen_cpus,
> -                  numa_info[i].node_cpu, MAX_CPUMASK_BITS);
> +                  numa_info[i].node_cpu, max_cpus);
>      }
>  
>      if (!bitmap_full(seen_cpus, max_cpus)) {
> @@ -291,12 +291,17 @@ static void validate_numa_cpus(void)
>                       "in NUMA config");
>          g_free(msg);
>      }
> +    bitmap_free(seen_cpus);

See comment about bitmap_free() on patch 1/2. I think g_free() is
good enough (unless you really want to review all callers of
bitmap_[try_]new()).

>  }
>  
>  void parse_numa_opts(MachineClass *mc)
>  {
>      int i;
>  
> +    for (i = 0; i < MAX_NODES; i++) {
> +        numa_info[i].node_cpu = bitmap_new(max_cpus);
> +    }
> +
>      if (qemu_opts_foreach(qemu_find_opts("numa"), parse_numa, NULL, NULL)) {
>          exit(1);
>      }
> @@ -362,7 +367,7 @@ void parse_numa_opts(MachineClass *mc)
>          numa_set_mem_ranges();
>  
>          for (i = 0; i < nb_numa_nodes; i++) {
> -            if (!bitmap_empty(numa_info[i].node_cpu, MAX_CPUMASK_BITS)) {
> +            if (!bitmap_empty(numa_info[i].node_cpu, max_cpus)) {
>                  break;
>              }
>          }
> diff --git a/vl.c b/vl.c
> index d77dd86..37790e5 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -1277,11 +1277,6 @@ static void smp_parse(QemuOpts *opts)
>  
>          max_cpus = qemu_opt_get_number(opts, "maxcpus", cpus);
>  
> -        if (max_cpus > MAX_CPUMASK_BITS) {
> -            error_report("unsupported number of maxcpus");
> -            exit(1);
> -        }
> -
>          if (max_cpus < cpus) {
>              error_report("maxcpus must be equal to or greater than smp");
>              exit(1);
> -- 
> 2.7.4
> 

-- 
Eduardo