Re: [Qemu-devel] [PATCH v5 1/3] hw/acpi-build: Fix SRAT memory building in case of node 0 without RAM

[Igor Mammedov <imammedo@redhat.com>]

On Mon, 4 Sep 2017 18:16:31 +0800
Dou Liyang <douly.fnst@cn.fujitsu.com> wrote:

> At 09/04/2017 05:39 PM, Igor Mammedov wrote:
> > On Thu, 31 Aug 2017 20:04:26 +0800
> > Dou Liyang <douly.fnst@cn.fujitsu.com> wrote:
> >  
> >> From: Eduardo Habkost <ehabkost@redhat.com>
> >>
> >> 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 node 0 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  cut out the 640K hole in the same way the PCI
> >> 4G hole does. Also do some cleanup.
> >>
> >> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> >> Signed-off-by: Dou Liyang <douly.fnst@cn.fujitsu.com>
> >> ---
> >>  hw/i386/acpi-build.c | 30 +++++++++++++++++++++++-------
> >>  1 file changed, 23 insertions(+), 7 deletions(-)
> >>
> >> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> >> index 98dd424..48525a1 100644
> >> --- a/hw/i386/acpi-build.c
> >> +++ b/hw/i386/acpi-build.c
> >> @@ -2318,6 +2318,9 @@ build_tpm2(GArray *table_data, BIOSLinker *linker)
> >>                   (void *)tpm2_ptr, "TPM2", sizeof(*tpm2_ptr), 4, NULL, NULL);
> >>  }
> >>
> >> +#define HOLE_640K_START  (640 * 1024)
> >> +#define HOLE_640K_END   (1024 * 1024)
> >> +
> >>  static void
> >>  build_srat(GArray *table_data, BIOSLinker *linker, MachineState *machine)
> >>  {
> >> @@ -2373,17 +2376,30 @@ build_srat(GArray *table_data, BIOSLinker *linker, MachineState *machine)
> >>      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;
> >> -        }
> >>          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_START;
> >> +            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);
> >> +            }
> >> +
> >> +            /* Check for the rare case: 640K < RAM < 1M */
> >> +            if (next_base <= HOLE_640K_END) {
> >> +                next_base = HOLE_640K_END;  
> > Is this assignment really necessary?
> >  
> 
> It is necessary, because we set mem_base to next_base before setting
> next_base;
> 
> But, I can refine it:
> 
>                                     MEM_AFFINITY_ENABLED);
>               }
> 
> +            mem_base = HOLE_640K_END;
>               /* Check for the rare case: 640K < RAM < 1M */
>               if (next_base <= HOLE_640K_END) {
> -                next_base = HOLE_640K_END;
>                   continue;
>               }
> -            mem_base = HOLE_640K_END;
>               mem_len = next_base - HOLE_640K_END;
>           }
> 
> Is it?
I was wrong, so just leave it as it is now.

> 
> Thanks,
> 	dou.
> 
> > it seems that next_base will be set at the start of the loop.
> >  
> 
> 
> >> +                continue;
> >> +            }
> >> +            mem_base = HOLE_640K_END;
> >> +            mem_len = next_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) {
> >> @@ -2395,7 +2411,7 @@ build_srat(GArray *table_data, BIOSLinker *linker, MachineState *machine)
> >>              }
> >>              mem_base = 1ULL << 32;
> >>              mem_len = next_base - pcms->below_4g_mem_size;
> >> -            next_base += (1ULL << 32) - pcms->below_4g_mem_size;
> >> +            next_base = mem_base + mem_len;
> >>          }
> >>          numamem = acpi_data_push(table_data, sizeof *numamem);
> >>          build_srat_memory(numamem, mem_base, mem_len, i - 1,  
> >
> >
> >
> >  
> 
>