Re: [Qemu-devel] [PATCH v9] Allow setting NUMA distance for different NUMA nodes

[Andrew Jones]

On Thu, Apr 27, 2017 at 10:35:58AM +0800, He Chen wrote:
> This patch is going to add SLIT table support in QEMU, and provides
> additional option `dist` for command `-numa` to allow user set vNUMA
> distance by QEMU command.
> 
> With this patch, when a user wants to create a guest that contains
> several vNUMA nodes and also wants to set distance among those nodes,
> the QEMU command would like:
> 
> ```
> -numa node,nodeid=0,cpus=0 \
> -numa node,nodeid=1,cpus=1 \
> -numa node,nodeid=2,cpus=2 \
> -numa node,nodeid=3,cpus=3 \
> -numa dist,src=0,dst=1,val=21 \
> -numa dist,src=0,dst=2,val=31 \
> -numa dist,src=0,dst=3,val=41 \
> -numa dist,src=1,dst=2,val=21 \
> -numa dist,src=1,dst=3,val=31 \
> -numa dist,src=2,dst=3,val=21 \
> ```
> 
> Signed-off-by: He Chen <address@hidden>
> 
> ---
> Changes since v8:
> * numa_{node, distance}_parse --> parse_numa_{node, distance}
> * Comments refinement.
> 
> Changes since v7:
> * Remove unnecessary node present check.
> * Minor improvement on prompt message.
> 
> Changes since v6:
> * Split validate_numa_distance into 2 separate functions.
> * Add comments before validate and complete numa distance functions.
> 
> Changes since v5:
> * Made the generation of the SLIT dependent on `have_numa_distance`.
> * Doc refinement.
> ---
>  hw/acpi/aml-build.c         |  26 +++++++++
>  hw/i386/acpi-build.c        |   4 ++
>  include/hw/acpi/aml-build.h |   1 +
>  include/sysemu/numa.h       |   2 +
>  include/sysemu/sysemu.h     |   4 ++
>  numa.c                      | 137 
> +++++++++++++++++++++++++++++++++++++++++++-
>  qapi-schema.json            |  30 +++++++++-
>  qemu-options.hx             |  16 +++++-
>  8 files changed, 215 insertions(+), 5 deletions(-)
> 
> diff --git a/hw/acpi/aml-build.c b/hw/acpi/aml-build.c
> index c6f2032..be496c8 100644
> --- a/hw/acpi/aml-build.c
> +++ b/hw/acpi/aml-build.c
> @@ -24,6 +24,7 @@
>  #include "hw/acpi/aml-build.h"
>  #include "qemu/bswap.h"
>  #include "qemu/bitops.h"
> +#include "sysemu/numa.h"
>  
>  static GArray *build_alloc_array(void)
>  {
> @@ -1609,3 +1610,28 @@ void build_srat_memory(AcpiSratMemoryAffinity 
> *numamem, uint64_t base,
>      numamem->base_addr = cpu_to_le64(base);
>      numamem->range_length = cpu_to_le64(len);
>  }
> +
> +/*
> + * ACPI spec 5.2.17 System Locality Distance Information Table
> + * (Revision 2.0 or later)
> + */
> +void build_slit(GArray *table_data, BIOSLinker *linker)
> +{
> +    int slit_start, i, j;
> +    slit_start = table_data->len;
> +
> +    acpi_data_push(table_data, sizeof(AcpiTableHeader));
> +
> +    build_append_int_noprefix(table_data, nb_numa_nodes, 8);
> +    for (i = 0; i < nb_numa_nodes; i++) {
> +        for (j = 0; j < nb_numa_nodes; j++) {
> +            assert(numa_info[i].distance[j]);
> +            build_append_int_noprefix(table_data, numa_info[i].distance[j], 
> 1);
> +        }
> +    }
> +
> +    build_header(linker, table_data,
> +                 (void *)(table_data->data + slit_start),
> +                 "SLIT",
> +                 table_data->len - slit_start, 1, NULL, NULL);
> +}
> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> index 2073108..2458ebc 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -2678,6 +2678,10 @@ void acpi_build(AcpiBuildTables *tables, MachineState 
> *machine)
>      if (pcms->numa_nodes) {
>          acpi_add_table(table_offsets, tables_blob);
>          build_srat(tables_blob, tables->linker, machine);
> +        if (have_numa_distance) {
> +            acpi_add_table(table_offsets, tables_blob);
> +            build_slit(tables_blob, tables->linker);
> +        }
>      }
>      if (acpi_get_mcfg(&mcfg)) {
>          acpi_add_table(table_offsets, tables_blob);
> diff --git a/include/hw/acpi/aml-build.h b/include/hw/acpi/aml-build.h
> index 00c21f1..329a0d0 100644
> --- a/include/hw/acpi/aml-build.h
> +++ b/include/hw/acpi/aml-build.h
> @@ -389,4 +389,5 @@ GCC_FMT_ATTR(2, 3);
>  void build_srat_memory(AcpiSratMemoryAffinity *numamem, uint64_t base,
>                         uint64_t len, int node, MemoryAffinityFlags flags);
>  
> +void build_slit(GArray *table_data, BIOSLinker *linker);
>  #endif
> diff --git a/include/sysemu/numa.h b/include/sysemu/numa.h
> index 8f09dcf..0ea1bc0 100644
> --- a/include/sysemu/numa.h
> +++ b/include/sysemu/numa.h
> @@ -8,6 +8,7 @@
>  #include "hw/boards.h"
>  
>  extern int nb_numa_nodes;   /* Number of NUMA nodes */
> +extern bool have_numa_distance;
>  
>  struct numa_addr_range {
>      ram_addr_t mem_start;
> @@ -21,6 +22,7 @@ typedef struct node_info {
>      struct HostMemoryBackend *node_memdev;
>      bool present;
>      QLIST_HEAD(, numa_addr_range) addr; /* List to store address ranges */
> +    uint8_t distance[MAX_NODES];
>  } NodeInfo;
>  
>  extern NodeInfo numa_info[MAX_NODES];
> diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
> index 576c7ce..6999545 100644
> --- a/include/sysemu/sysemu.h
> +++ b/include/sysemu/sysemu.h
> @@ -169,6 +169,10 @@ extern int mem_prealloc;
>  
>  #define MAX_NODES 128
>  #define NUMA_NODE_UNASSIGNED MAX_NODES
> +#define NUMA_DISTANCE_MIN         10
> +#define NUMA_DISTANCE_DEFAULT     20
> +#define NUMA_DISTANCE_MAX         254
> +#define NUMA_DISTANCE_UNREACHABLE 255
>  
>  #define MAX_OPTION_ROMS 16
>  typedef struct QEMUOptionRom {
> diff --git a/numa.c b/numa.c
> index 6fc2393..2b3fc69 100644
> --- a/numa.c
> +++ b/numa.c
> @@ -51,6 +51,7 @@ static int max_numa_nodeid; /* Highest specified NUMA node 
> ID, plus one.
>                               * For all nodes, nodeid < max_numa_nodeid
>                               */
>  int nb_numa_nodes;
> +bool have_numa_distance;
>  NodeInfo numa_info[MAX_NODES];
>  
>  void numa_set_mem_node_id(ram_addr_t addr, uint64_t size, uint32_t node)
> @@ -140,7 +141,7 @@ uint32_t numa_get_node(ram_addr_t addr, Error **errp)
>      return -1;
>  }
>  
> -static void numa_node_parse(NumaNodeOptions *node, QemuOpts *opts, Error 
> **errp)
> +static void parse_numa_node(NumaNodeOptions *node, QemuOpts *opts, Error 
> **errp)
>  {
>      uint16_t nodenr;
>      uint16List *cpus = NULL;
> @@ -212,6 +213,43 @@ static void numa_node_parse(NumaNodeOptions *node, 
> QemuOpts *opts, Error **errp)
>      max_numa_nodeid = MAX(max_numa_nodeid, nodenr + 1);
>  }
>  
> +static void parse_numa_distance(NumaDistOptions *dist, Error **errp)
> +{
> +    uint16_t src = dist->src;
> +    uint16_t dst = dist->dst;
> +    uint8_t val = dist->val;
> +
> +    if (src >= MAX_NODES || dst >= MAX_NODES) {
> +        error_setg(errp,
> +                   "Invalid node %" PRIu16
> +                   ", max possible could be %" PRIu16,
> +                   MAX(src, dst), MAX_NODES);
> +        return;
> +    }
> +
> +    if (!numa_info[src].present || !numa_info[dst].present) {
> +        error_setg(errp, "Source/Destination NUMA node is missing. "
> +                   "Please use '-numa node' option to declare it first.");
> +        return;
> +    }
> +
> +    if (val < NUMA_DISTANCE_MIN) {
> +        error_setg(errp, "NUMA distance (%" PRIu8 ") is invalid, "
> +                   "it shouldn't be less than %d.",
> +                   val, NUMA_DISTANCE_MIN);
> +        return;
> +    }
> +
> +    if (src == dst && val != NUMA_DISTANCE_MIN) {
> +        error_setg(errp, "Local distance of node %d should be %d.",
> +                   src, NUMA_DISTANCE_MIN);
> +        return;
> +    }
> +
> +    numa_info[src].distance[dst] = val;
> +    have_numa_distance = true;
> +}
> +
>  static int parse_numa(void *opaque, QemuOpts *opts, Error **errp)
>  {
>      NumaOptions *object = NULL;
> @@ -229,12 +267,18 @@ static int parse_numa(void *opaque, QemuOpts *opts, 
> Error **errp)
>  
>      switch (object->type) {
>      case NUMA_OPTIONS_TYPE_NODE:
> -        numa_node_parse(&object->u.node, opts, &err);
> +        parse_numa_node(&object->u.node, opts, &err);
>          if (err) {
>              goto end;
>          }
>          nb_numa_nodes++;
>          break;
> +    case NUMA_OPTIONS_TYPE_DIST:
> +        parse_numa_distance(&object->u.dist, &err);
> +        if (err) {
> +            goto end;
> +        }
> +        break;
>      default:
>          abort();
>      }
> @@ -294,6 +338,75 @@ static void validate_numa_cpus(void)
>      g_free(seen_cpus);
>  }
>  
> +/* If all node pair distances are symmetric, then only distances
> + * in one direction are enough. If there is even one asymmetric
> + * pair, though, then all distances must be provided. The
> + * distance from a node to itself is always NUMA_DISTANCE_MIN,
> + * so providing it is never necessary.
> + */
> +static void validate_numa_distance(void)
> +{
> +    int src, dst;
> +    bool is_asymmetrical = false;
> +
> +    for (src = 0; src < nb_numa_nodes; src++) {
> +        for (dst = src; dst < nb_numa_nodes; dst++) {
> +            if (numa_info[src].distance[dst] == 0 &&
> +                numa_info[dst].distance[src] == 0) {
> +                if (src != dst) {
> +                    error_report("The distance between node %d and %d is "
> +                                 "missing, at least one distance value "
> +                                 "between each nodes should be provided.",
> +                                 src, dst);
> +                    exit(EXIT_FAILURE);
> +                }
> +            }
> +
> +            if (numa_info[src].distance[dst] != 0 &&
> +                numa_info[dst].distance[src] != 0 &&
> +                numa_info[src].distance[dst] !=
> +                numa_info[dst].distance[src]) {
> +                is_asymmetrical = true;
> +            }
> +        }
> +    }
> +
> +    if (is_asymmetrical) {
> +        for (src = 0; src < nb_numa_nodes; src++) {
> +            for (dst = 0; dst < nb_numa_nodes; dst++) {
> +                if (src != dst && numa_info[src].distance[dst] == 0) {
> +                    error_report("At least one asymmetrical pair of "
> +                            "distances is given, please provide distances "
> +                            "for both directions of all node pairs.");
> +                    exit(EXIT_FAILURE);
> +                }
> +            }
> +        }
> +    }
> +}
> +
> +static void complete_init_numa_distance(void)
> +{
> +    int src, dst;
> +
> +    /* Fixup NUMA distance by symmetric policy because if it is an
> +     * asymmetric distance table, it should be a complete table and
> +     * there would not be any missing distance except local node, which
> +     * is verified by validate_numa_distance above.
> +     */
> +    for (src = 0; src < nb_numa_nodes; src++) {
> +        for (dst = 0; dst < nb_numa_nodes; dst++) {
> +            if (numa_info[src].distance[dst] == 0) {
> +                if (src == dst) {
> +                    numa_info[src].distance[dst] = NUMA_DISTANCE_MIN;
> +                } else {
> +                    numa_info[src].distance[dst] = 
> numa_info[dst].distance[src];
> +                }
> +            }
> +        }
> +    }
> +}
> +
>  void parse_numa_opts(MachineClass *mc)
>  {
>      int i;
> @@ -390,6 +503,26 @@ void parse_numa_opts(MachineClass *mc)
>          }
>  
>          validate_numa_cpus();
> +
> +        /* QEMU needs at least all unique node pair distances to build
> +         * the whole NUMA distance table. QEMU treats the distance table
> +         * as symmetric by default, i.e. distance A->B == distance B->A.
> +         * Thus, QEMU is able to complete the distance table
> +         * initialization even though only distance A->B is provided and
> +         * distance B->A is not. QEMU knows the distance of a node to
> +         * itself is always 10, so A->A distances may be omitted. When
> +         * the distances of two nodes of a pair differ, i.e. distance
> +         * A->B != distance B->A, then that means the distance table is
> +         * asymmetric. In this case, the distances for both directions
> +         * of all node pairs are required.
> +         */

I was thinking you'd either keep the above comment (with the edits I
suggested, and as you've done) or the suggestion to just comment each of
the two functions, validate_numa_distance and complete_init_numa_distance,
above (also as you've done), but then do almost nothing here, except the
two one line comments below.  IOW, since you've added the comments above,
this one could have been dropped.  That said, I'm not opposed to both, but
it does add potential maintenance.  If the code were to change, then we
have another comment to update.

> +        if (have_numa_distance) {
> +            /* Validate enough NUMA distance information was provided. */
> +            validate_numa_distance();
> +
> +            /* Validation succeeded, now fill in any missing distances. */
> +            complete_init_numa_distance();
> +        }
>      } else {
>          numa_set_mem_node_id(0, ram_size, 0);
>      }
> diff --git a/qapi-schema.json b/qapi-schema.json
> index 250e4dc..92fcd18 100644
> --- a/qapi-schema.json
> +++ b/qapi-schema.json
> @@ -5673,10 +5673,14 @@
>  ##
>  # @NumaOptionsType:
>  #
> +# @node: NUMA nodes configuration
> +#
> +# @dist: NUMA distance configuration (since 2.10)
> +#
>  # Since: 2.1
>  ##
>  { 'enum': 'NumaOptionsType',
> -  'data': [ 'node' ] }
> +  'data': [ 'node', 'dist' ] }
>  
>  ##
>  # @NumaOptions:
> @@ -5689,7 +5693,8 @@
>    'base': { 'type': 'NumaOptionsType' },
>    'discriminator': 'type',
>    'data': {
> -    'node': 'NumaNodeOptions' }}
> +    'node': 'NumaNodeOptions',
> +    'dist': 'NumaDistOptions' }}
>  
>  ##
>  # @NumaNodeOptions:
> @@ -5718,6 +5723,27 @@
>     '*memdev': 'str' }}
>  
>  ##
> +# @NumaDistOptions:
> +#
> +# Set the distance between 2 NUMA nodes.
> +#
> +# @src: source NUMA node.
> +#
> +# @dst: destination NUMA node.
> +#
> +# @val: NUMA distance from source node to destination node.
> +#       When a node is unreachable from another node, set the distance
> +#       between them to 255.
> +#
> +# Since: 2.10
> +##
> +{ 'struct': 'NumaDistOptions',
> +  'data': {
> +   'src': 'uint16',
> +   'dst': 'uint16',
> +   'val': 'uint8' }}
> +
> +##
>  # @HostMemPolicy:
>  #
>  # Host memory policy types
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 99af8ed..7823db8 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -139,12 +139,15 @@ ETEXI
>  
>  DEF("numa", HAS_ARG, QEMU_OPTION_numa,
>      "-numa node[,mem=size][,cpus=firstcpu[-lastcpu]][,nodeid=node]\n"
> -    "-numa node[,memdev=id][,cpus=firstcpu[-lastcpu]][,nodeid=node]\n", 
> QEMU_ARCH_ALL)
> +    "-numa node[,memdev=id][,cpus=firstcpu[-lastcpu]][,nodeid=node]\n"
> +    "-numa dist,src=source,dst=destination,val=distance\n", QEMU_ARCH_ALL)
>  STEXI
>  @item -numa 
> node[,address@hidden,address@hidden@var{lastcpu}]][,address@hidden
>  @itemx -numa 
> node[,address@hidden,address@hidden@var{lastcpu}]][,address@hidden
> address@hidden -numa dist,address@hidden,address@hidden,address@hidden
>  @findex -numa
>  Define a NUMA node and assign RAM and VCPUs to it.
> +Set the NUMA distance from a source node to a destination node.
>  
>  @var{firstcpu} and @var{lastcpu} are CPU indexes. Each
>  @samp{cpus} option represent a contiguous range of CPU indexes
> @@ -167,6 +170,17 @@ split equally between them.
>  @samp{mem} and @samp{memdev} are mutually exclusive. Furthermore,
>  if one node uses @samp{memdev}, all of them have to use it.
>  
> address@hidden and @var{destination} are NUMA node IDs.
> address@hidden is the NUMA distance from @var{source} to @var{destination}.
> +The distance from a node to itself is always 10. If any pair of nodes is
> +given a distance, then all pairs must be given distances. Although, when
> +distances are only given in one direction for each pair of nodes, then
> +the distances in the opposite directions are assumed to be the same. If,
> +however, an asymmetrical pair of distances is given for even one node
> +pair, then all node pairs must be provided distance values for both
> +directions, even when they are symmetrical. When a node is unreachable
> +from another node, set the pair's distance to 255.
> +
>  Note that the address@hidden option doesn't allocate any of the
>  specified resources, it just assigns existing resources to NUMA
>  nodes. This means that one still has to use the @option{-m},
> -- 
> 2.7.4
> 
>

Reviewed-by: Andrew Jones <address@hidden>

Thanks,
drew