Re: [Qemu-devel] [PATCH v4 1/2] hw/acpi-build: Fix SRAT memory building when there is no memory in node0

[Eduardo Habkost <ehabkost@redhat.com>]

On Tue, Aug 22, 2017 at 11:24:09AM +0800, Dou Liyang wrote:
> Currently, Using the fisrt node without memory on the machine makes
> QEMU unhappy. With this example command line:
>   ... \
>   -m 1024M,slots=4,maxmem=32G \
>   -numa node,nodeid=0 \
>   -numa node,mem=1024M,nodeid=1 \
>   -numa node,nodeid=2 \
>   -numa node,nodeid=3 \
> Guest reports "No NUMA configuration found" and the NUMA topology is
> wrong.
> 
> This is because when QEMU builds ACPI SRAT, it regards node0 as the
> default node to deal with the memory hole(640K-1M). this means the
> node0 must have some memory(>1M), but, actually it can have no
> memory.
> 
> Fix this problem by replace the node0 with the first node which has
> memory on it. Add a new function for each node. Also do some cleanup.
> 
> Signed-off-by: Dou Liyang <douly.fnst@cn.fujitsu.com>
> ---
>  hw/i386/acpi-build.c | 78 +++++++++++++++++++++++++++++++++-------------------
>  1 file changed, 50 insertions(+), 28 deletions(-)
> 
> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> index 98dd424..f93d712 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -2318,15 +2318,43 @@ build_tpm2(GArray *table_data, BIOSLinker *linker)
>                   (void *)tpm2_ptr, "TPM2", sizeof(*tpm2_ptr), 4, NULL, NULL);
>  }
>  
> +static uint64_t
> +build_srat_node_entry(GArray *table_data, PCMachineState *pcms,
> +                                int i, uint64_t mem_base, uint64_t mem_len)
> +{
> +    AcpiSratMemoryAffinity *numamem;
> +    uint64_t next_base;
> +
> +    next_base = mem_base + mem_len;
> +
> +    /* Cut out the ACPI_PCI hole */
> +    if (mem_base <= pcms->below_4g_mem_size &&
> +        next_base > pcms->below_4g_mem_size) {
> +        mem_len -= next_base - pcms->below_4g_mem_size;
> +        if (mem_len > 0) {
> +            numamem = acpi_data_push(table_data, sizeof *numamem);
> +            build_srat_memory(numamem, mem_base, mem_len, i,
> +                              MEM_AFFINITY_ENABLED);
> +        }
> +        mem_base = 1ULL << 32;
> +        mem_len = next_base - pcms->below_4g_mem_size;
> +        next_base += (1ULL << 32) - pcms->below_4g_mem_size;
> +    }
> +    numamem = acpi_data_push(table_data, sizeof *numamem);
> +    build_srat_memory(numamem, mem_base, mem_len, i,
> +                      MEM_AFFINITY_ENABLED);
> +    return next_base;
> +}
> +
>  static void
>  build_srat(GArray *table_data, BIOSLinker *linker, MachineState *machine)
>  {
>      AcpiSystemResourceAffinityTable *srat;
>      AcpiSratMemoryAffinity *numamem;
>  
> -    int i;
> +    int i, node;
>      int srat_start, numa_start, slots;
> -    uint64_t mem_len, mem_base, next_base;
> +    uint64_t mem_len, mem_base;
>      MachineClass *mc = MACHINE_GET_CLASS(machine);
>      const CPUArchIdList *apic_ids = mc->possible_cpu_arch_ids(machine);
>      PCMachineState *pcms = PC_MACHINE(machine);
> @@ -2370,36 +2398,30 @@ build_srat(GArray *table_data, BIOSLinker *linker, MachineState *machine)
>      /* the memory map is a bit tricky, it contains at least one hole
>       * from 640k-1M and possibly another one from 3.5G-4G.
>       */
> -    next_base = 0;
> +
>      numa_start = table_data->len;
>  
> -    numamem = acpi_data_push(table_data, sizeof *numamem);
> -    build_srat_memory(numamem, 0, 640 * 1024, 0, MEM_AFFINITY_ENABLED);
> -    next_base = 1024 * 1024;
> -    for (i = 1; i < pcms->numa_nodes + 1; ++i) {
> -        mem_base = next_base;
> -        mem_len = pcms->node_mem[i - 1];
> -        if (i == 1) {
> -            mem_len -= 1024 * 1024;
> +    /* get the first node which has memory and map the hole from 640K-1M */
> +    for (node = 0; node < pcms->numa_nodes; node++) {
> +        if (pcms->node_mem[node] != 0) {
> +            break;
>          }
> -        next_base = mem_base + mem_len;
> -
> -        /* Cut out the ACPI_PCI hole */
> -        if (mem_base <= pcms->below_4g_mem_size &&
> -            next_base > pcms->below_4g_mem_size) {
> -            mem_len -= next_base - pcms->below_4g_mem_size;
> -            if (mem_len > 0) {
> -                numamem = acpi_data_push(table_data, sizeof *numamem);
> -                build_srat_memory(numamem, mem_base, mem_len, i - 1,
> -                                  MEM_AFFINITY_ENABLED);
> -            }
> -            mem_base = 1ULL << 32;
> -            mem_len = next_base - pcms->below_4g_mem_size;
> -            next_base += (1ULL << 32) - pcms->below_4g_mem_size;
> +    }
> +    numamem = acpi_data_push(table_data, sizeof *numamem);
> +    build_srat_memory(numamem, 0, 640 * 1024, node, MEM_AFFINITY_ENABLED);
> +
> +    /* map the rest of memory from 1M */
> +    mem_base = 1024 * 1024;
> +    mem_len = pcms->node_mem[node] - mem_base;
> +    mem_base = build_srat_node_entry(table_data, pcms, node,
> +                                            mem_base, mem_len);
> +
> +    for (i = 0; i < pcms->numa_nodes; i++) {
> +        if (i == node) {
> +            continue;
>          }

Now the nodes will be out of order, if node 0 has no RAM.  Why?

Why not implement this in the same way the PCI 4GB hole is
already implemented.  e.g.:

#define HOLE_640K_START  (640 * 1024)
#define HOLE_640K_END   (1024 * 1024)

    for (node = 0; node < pcms->numa_nodes; node++) {
        mem_base = next_base;
        mem_len = pcms->node_mem[node];
        next_base = mem_base + mem_len;

        /* Cut out the 640K hole */
        if (mem_base <= HOLE_640K_START &&
            next_base > HOLE_640K_START) {
            mem_len -= next_base - HOLE_640K;
            if (mem_len > 0) {
                numamem = acpi_data_push(table_data, sizeof *numamem);
                build_srat_memory(numamem, mem_base, mem_len, node,
                                  MEM_AFFINITY_ENABLED);
            }
            mem_base = HOLE_640K_END;
            /* ... */
        }
        /* Cut out the ACPI_PCI hole */
        if (mem_base <= pcms->below_4g_mem_size &&
            next_base > pcms->below_4g_mem_size) {
            mem_len -= next_base - pcms->below_4g_mem_size;
            /* ... *]
        }
        numamem = acpi_data_push(table_data, sizeof *numamem);
        build_srat_memory(numamem, mem_base, mem_len, node,
                          MEM_AFFINITY_ENABLED);
        /* ... */
    }

> -        numamem = acpi_data_push(table_data, sizeof *numamem);
> -        build_srat_memory(numamem, mem_base, mem_len, i - 1,
> -                          MEM_AFFINITY_ENABLED);
> +        mem_base = build_srat_node_entry(table_data, pcms, i,
> +                                            mem_base, pcms->node_mem[i]);
>      }
>      slots = (table_data->len - numa_start) / sizeof *numamem;
>      for (; slots < pcms->numa_nodes + 2; slots++) {
> -- 
> 2.5.5
> 
> 
> 
> 

-- 
Eduardo