Re: [Qemu-devel] [RFC PATCH v0 1/5] spapr: Provide better error message when slots exceed max allowed

[David Gibson <david@gibson.dropbear.id.au>]

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On Mon, Aug 03, 2015 at 11:05:39AM +0530, Bharata B Rao wrote:
> Currently when user specifies more slots than allowed max of
> SPAPR_MAX_RAM_SLOTS (32), we error out like this:
> 
> qemu-system-ppc64: unsupported amount of memory slots: 64
> 
> Let the user know about the max allowed slots like this:
> 
> qemu-system-ppc64: Specified number of memory slots 64 exceeds max supported 32
> 
> Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>

So, this is good as far as it goes.  There's another problem here
though.

At present even requesting 32 slots will not work properly, because
KVM only supports 32 slots and a couple of those are already used for
the non-hotplug RAM.  I think fixing this requires a kernel change to
advertise the available KVM memory slots.

> ---
>  hw/ppc/spapr.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 6e24bf9..6d9cbd9 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -1777,8 +1777,8 @@ static void ppc_spapr_init(MachineState *machine)
>          ram_addr_t hotplug_mem_size = machine->maxram_size - machine->ram_size;
>  
>          if (machine->ram_slots > SPAPR_MAX_RAM_SLOTS) {
> -            error_report("unsupported amount of memory slots: %"PRIu64,
> -                          machine->ram_slots);
> +            error_report("Specified number of memory slots %"PRIu64" exceeds max supported %d\n",
> +                         machine->ram_slots, SPAPR_MAX_RAM_SLOTS);
>              exit(EXIT_FAILURE);
>          }
>  

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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