Re: [PATCH v12 09/11] hmat acpi: Build System Locality Latency and Bandwidth Information Structure(s)

[Igor Mammedov <imammedo@redhat.com>]

On Fri, 20 Sep 2019 15:43:47 +0800
Tao Xu <tao3.xu@intel.com> wrote:

> From: Liu Jingqi <jingqi.liu@intel.com>
> 
> This structure describes the memory access latency and bandwidth
> information from various memory access initiator proximity domains.
> The latency and bandwidth numbers represented in this structure
> correspond to rated latency and bandwidth for the platform.
> The software could use this information as hint for optimization.
> 
> Signed-off-by: Liu Jingqi <jingqi.liu@intel.com>
> Signed-off-by: Tao Xu <tao3.xu@intel.com>
> ---
> 
> Changes in v12:
>     - Fix a bug that if HMAT is enabled and without hmat-lb setting,
>       QEMU will crash. (reported by Danmei Wei)
> 
> Changes in v11:
>     - Calculate base in build_hmat_lb().
> ---
>  hw/acpi/hmat.c | 126 ++++++++++++++++++++++++++++++++++++++++++++++++-
>  hw/acpi/hmat.h |   2 +
>  2 files changed, 127 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/acpi/hmat.c b/hw/acpi/hmat.c
> index 1368fce7ee..e7be849581 100644
> --- a/hw/acpi/hmat.c
> +++ b/hw/acpi/hmat.c
> @@ -27,6 +27,7 @@
>  #include "qemu/osdep.h"
>  #include "sysemu/numa.h"
>  #include "hw/acpi/hmat.h"
> +#include "qemu/error-report.h"
>  
>  /*
>   * ACPI 6.3:
> @@ -67,11 +68,105 @@ static void build_hmat_mpda(GArray *table_data, uint16_t flags, int initiator,
>      build_append_int_noprefix(table_data, 0, 8);
>  }
>  
> +static bool entry_overflow(uint64_t *lb_data, uint64_t base, int len)
> +{
> +    int i;
> +
> +    for (i = 0; i < len; i++) {
> +        if (lb_data[i] / base >= UINT16_MAX) {
> +            return true;
> +        }
> +    }
> +
> +    return false;
> +}
I suggest to do this check at CLI parsing time

> +/*
> + * ACPI 6.3: 5.2.27.4 System Locality Latency and Bandwidth Information
> + * Structure: Table 5-146
> + */
> +static void build_hmat_lb(GArray *table_data, HMAT_LB_Info *hmat_lb,
> +                          uint32_t num_initiator, uint32_t num_target,
> +                          uint32_t *initiator_list, int type)
> +{
> +    uint8_t mask = 0x0f; 
> +    uint32_t s = num_initiator;
> +    uint32_t t = num_target;
drop this locals and use arguments directly

> +    uint64_t base = 1;
> +    uint64_t *lb_data;
> +    int i, unit;
> +
> +    /* Type */
> +    build_append_int_noprefix(table_data, 1, 2);
> +    /* Reserved */
> +    build_append_int_noprefix(table_data, 0, 2);
> +    /* Length */
> +    build_append_int_noprefix(table_data, 32 + 4 * s + 4 * t + 2 * s * t, 4);
                                             ^^^^
to me above looks like /dev/random output, absolutely unreadable.
Suggest to use local var (like: lb_length) for expression with comments
beside magic numbers.

> +    /* Flags: Bits [3:0] Memory Hierarchy, Bits[7:4] Reserved */
> +    build_append_int_noprefix(table_data, hmat_lb->hierarchy & mask, 1);

why do you need to use mask here?

> +    /* Data Type */
> +    build_append_int_noprefix(table_data, hmat_lb->data_type, 1);

Isn't hmat_lb->data_type and passed argument 'type' the same?


> +    /* Reserved */
> +    build_append_int_noprefix(table_data, 0, 2);
> +    /* Number of Initiator Proximity Domains (s) */
> +    build_append_int_noprefix(table_data, s, 4);
> +    /* Number of Target Proximity Domains (t) */
> +    build_append_int_noprefix(table_data, t, 4);
> +    /* Reserved */
> +    build_append_int_noprefix(table_data, 0, 4);
> +
> +    if (HMAT_IS_LATENCY(type)) {
> +        unit = 1000;
> +        lb_data = hmat_lb->latency;
> +    } else {
> +        unit = 1024;
> +        lb_data = hmat_lb->bandwidth;
> +    }
> +
> +    while (entry_overflow(lb_data, base, s * t)) {
> +        for (i = 0; i < s * t; i++) {
> +            if (!QEMU_IS_ALIGNED(lb_data[i], unit * base)) {
> +                error_report("Invalid latency/bandwidth input, all "
> +                "latencies/bandwidths should be specified in the same units.");
> +                exit(1);
> +            }
> +        }
> +        base *= unit;
> +    }
Can you clarify what you are trying to check here?

> +
> +    /* Entry Base Unit */
> +    build_append_int_noprefix(table_data, base, 8);
> +
> +    /* Initiator Proximity Domain List */
> +    for (i = 0; i < s; i++) {
> +        build_append_int_noprefix(table_data, initiator_list[i], 4);
> +    }
> +
> +    /* Target Proximity Domain List */
> +    for (i = 0; i < t; i++) {
> +        build_append_int_noprefix(table_data, i, 4);
> +    }
> +
> +    /* Latency or Bandwidth Entries */
> +    for (i = 0; i < s * t; i++) {
> +        uint16_t entry;
> +
> +        if (HMAT_IS_LATENCY(type)) {
drop if condition and reuse lb_data, that you've just initialized above


> +            entry = hmat_lb->latency[i] / base;
...
> +            entry = hmat_lb->bandwidth[i] / base;
I'm not sure that above is correct.
Pls clarify math behind above 2 expressions

> +        }
> +
> +        build_append_int_noprefix(table_data, entry, 2);
> +    }
> +}
> +
>  /* Build HMAT sub table structures */
>  static void hmat_build_table_structs(GArray *table_data, NumaState *nstat)
>  {
>      uint16_t flags;
> -    int i;
> +    uint32_t *initiator_list = NULL;
> +    int i, j, hrchy, type;
s/hrchy/hierarchy/

> +    HMAT_LB_Info *numa_hmat_lb;
>  
>      for (i = 0; i < nstat->num_nodes; i++) {
>          flags = 0;
> @@ -82,6 +177,35 @@ static void hmat_build_table_structs(GArray *table_data, NumaState *nstat)
>  
>          build_hmat_mpda(table_data, flags, nstat->nodes[i].initiator, i);
>      }
> +
> +    if (nstat->num_initiator) {
> +        initiator_list = g_malloc0(nstat->num_initiator * sizeof(uint32_t));
> +        for (i = 0, j = 0; i < nstat->num_nodes; i++) {
> +            if (nstat->nodes[i].has_cpu) {
> +                initiator_list[j] = i;
> +                j++;
> +            }
> +        }
> +    }
> +
> +    /*
> +     * ACPI 6.3: 5.2.27.4 System Locality Latency and Bandwidth Information
> +     * Structure: Table 5-146
> +     */
> +    for (hrchy = HMAT_LB_MEM_MEMORY;
> +         hrchy <= HMAT_LB_MEM_CACHE_3RD_LEVEL; hrchy++) {
> +        for (type = HMAT_LB_DATA_ACCESS_LATENCY;
> +             type <= HMAT_LB_DATA_WRITE_BANDWIDTH; type++) {
> +            numa_hmat_lb = nstat->hmat_lb[hrchy][type];
> +
> +            if (numa_hmat_lb) {
> +                build_hmat_lb(table_data, numa_hmat_lb, nstat->num_initiator,
> +                              nstat->num_nodes, initiator_list, type);
> +            }
> +        }
> +    }
> +
> +    g_free(initiator_list);
>  }
>  
>  void build_hmat(GArray *table_data, BIOSLinker *linker, NumaState *nstat)
> diff --git a/hw/acpi/hmat.h b/hw/acpi/hmat.h
> index 0c1839cf6f..1154dfb48e 100644
> --- a/hw/acpi/hmat.h
> +++ b/hw/acpi/hmat.h
> @@ -40,6 +40,8 @@
>   */
>  #define HMAT_PROX_INIT_VALID 0x1
>  
> +#define HMAT_IS_LATENCY(type) (type <= HMAT_LB_DATA_WRITE_LATENCY)

it's not worth to create macro for 1-off calculation, just drop it
and s/if (HMAT_IS_LATENCY(type))/if(type <= HMAT_LB_DATA_WRITE_LATENCY)/

> +
>  void build_hmat(GArray *table_data, BIOSLinker *linker, NumaState *nstat);
>  
>  #endif