Re: [PATCH 2/2] spapr.h: increase FDT_MAX_SIZE

[Cédric Le Goater]

On 4/8/21 10:40 PM, Daniel Henrique Barboza wrote:
> Certain SMP topologies stress, e.g. 1 thread/core, 2048 cores and
> 1 socket, stress the current maximum size of the pSeries FDT:
> 
> Calling ibm,client-architecture-support...qemu-system-ppc64: error
> creating device tree: (fdt_setprop(fdt, offset,
> "ibm,processor-segment-sizes", segs, sizeof(segs))): FDT_ERR_NOSPACE
> 
> 2048 is the default NR_CPUS value for the pSeries kernel. It's expected
> that users will want QEMU to be able to handle this kind of
> configuration.
> 
> Bumping FDT_MAX_SIZE to 2MB is enough for these setups to be created.
> 
> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
> ---
>  include/hw/ppc/spapr.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index bf7cab7a2c..3deb382678 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -95,7 +95,7 @@ typedef enum {
>  #define SPAPR_CAP_FIXED_CCD             0x03
>  #define SPAPR_CAP_FIXED_NA              0x10 /* Lets leave a bit of a gap... 
> */
>  
> -#define FDT_MAX_SIZE                    0x100000
> +#define FDT_MAX_SIZE                    0x200000
>  
>  /*
>   * NUMA related macros. MAX_DISTANCE_REF_POINTS was taken
> 

FYI,

On a very large system, I also had to bump the FDT_MAX_SIZE value in 
softmmu/device-tree.c because QEMU is parsing the host DT. 

Thanks,

C.