Re: [PATCH v6 17/18] spapr: Clean up RMA size calculation

[Philippe Mathieu-Daudé]

On 2/25/20 12:37 AM, David Gibson wrote:
> Move the calculation of the Real Mode Area (RMA) size into a helper
> function.  While we're there clean it up and correct it in a few ways:
>    * Add comments making it clearer where the various constraints come from
>    * Remove a pointless check that the RMA fits within Node 0 (we've just
>      clamped it so that it does)
>
> Signed-off-by: David Gibson <address@hidden>
> ---
>   hw/ppc/spapr.c | 59 ++++++++++++++++++++++++++++++--------------------
>   1 file changed, 35 insertions(+), 24 deletions(-)
>
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 6e9f15f64d..f0354b699d 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -2648,6 +2648,40 @@ static PCIHostState *spapr_create_default_phb(void)
>       return PCI_HOST_BRIDGE(dev);
>   }
>   
> +static hwaddr spapr_rma_size(SpaprMachineState *spapr, Error **errp)
> +{
> +    MachineState *machine = MACHINE(spapr);
> +    hwaddr rma_size = machine->ram_size;
> +    hwaddr node0_size = spapr_node0_size(machine);
> +
> +    /* RMA has to fit in the first NUMA node */
> +    rma_size = MIN(rma_size, node0_size);
> +
> +    /*
> +     * VRMA access is via a special 1TiB SLB mapping, so the RMA can
> +     * never exceed that
> +     */
> +    rma_size = MIN(rma_size, TiB);

Can you use '1 * TiB'? It makes review obvious.

> +
> +    /*
> +     * Clamp the RMA size based on machine type.  This is for
> +     * migration compatibility with older qemu versions, which limited
> +     * the RMA size for complicated and mostly bad reasons.
> +     */
> +    if (smc->rma_limit) {
> +        spapr->rma_size = MIN(spapr->rma_size, smc->rma_limit);
> +    }
> +
> +    if (rma_size < (MIN_RMA_SLOF * MiB)) {

This looks old copy/paste before the change "spapr: Don't use weird 
units for MIN_RMA_SLOF".

> +        error_setg(errp,
> +"pSeries SLOF firmware requires >= %ldMiB guest RMA (Real Mode Area)",
> +                   MIN_RMA_SLOF);

Similarly, "MIN_RMA_SLOF / MiB"?

> +        return -1;

Maybe return 0 in case this function is called with errp != &error_fatal.

> +    }
> +
> +    return rma_size;
> +}
> +
>   /* pSeries LPAR / sPAPR hardware init */
>   static void spapr_machine_init(MachineState *machine)
>   {
> @@ -2660,7 +2694,6 @@ static void spapr_machine_init(MachineState *machine)
>       int i;
>       MemoryRegion *sysmem = get_system_memory();
>       MemoryRegion *ram = g_new(MemoryRegion, 1);
> -    hwaddr node0_size = spapr_node0_size(machine);
>       long load_limit, fw_size;
>       char *filename;
>       Error *resize_hpt_err = NULL;
> @@ -2700,22 +2733,7 @@ static void spapr_machine_init(MachineState *machine)
>           exit(1);
>       }
>   
> -    spapr->rma_size = node0_size;
> -
> -    /*
> -     * Clamp the RMA size based on machine type.  This is for
> -     * migration compatibility with older qemu versions, which limited
> -     * the RMA size for complicated and mostly bad reasons.
> -     */
> -    if (smc->rma_limit) {
> -        spapr->rma_size = MIN(spapr->rma_size, smc->rma_limit);
> -    }
> -
> -    if (spapr->rma_size > node0_size) {
> -        error_report("Numa node 0 has to span the RMA (%#08"HWADDR_PRIx")",
> -                     spapr->rma_size);
> -        exit(1);
> -    }
> +    spapr->rma_size = spapr_rma_size(spapr, &error_fatal);
>   
>       /* Setup a load limit for the ramdisk leaving room for SLOF and FDT */
>       load_limit = MIN(spapr->rma_size, RTAS_MAX_ADDR) - FW_OVERHEAD;
> @@ -2954,13 +2972,6 @@ static void spapr_machine_init(MachineState *machine)
>           }
>       }
>   
> -    if (spapr->rma_size < MIN_RMA_SLOF) {
> -        error_report(
> -            "pSeries SLOF firmware requires >= %ldMiB guest RMA (Real Mode Area 
> memory)",
> -            MIN_RMA_SLOF / MiB);
> -        exit(1);
> -    }
> -
>       if (kernel_filename) {
>           uint64_t lowaddr = 0;
>