On 12/10/2016 06:44, David Gibson wrote:
> Currently the default PCI host bridge for the 'pseries' machine type is
> constructed with its IO windows in the 1TiB..(1TiB + 64GiB) range in
> guest memory space. This means that if > 1TiB of guest RAM is specified,
> the RAM will collide with the PCI IO windows, causing serious problems.
>
> Problems won't be obvious until guest RAM goes a bit beyond 1TiB, because
> there's a little unused space at the bottom of the area reserved for PCI,
> but essentially this means that > 1TiB of RAM has never worked with the
> pseries machine type.
>
> This patch fixes this by altering the placement of PHBs on large-RAM VMs.
> Instead of always placing the first PHB at 1TiB, it is placed at the next
> 1 TiB boundary after the maximum RAM address.
>
> Technically, this changes behaviour in a migration-breaking way for
> existing machines with > 1TiB maximum memory, but since having > 1 TiB
> memory was broken anyway, this seems like a reasonable trade-off.
>
> Signed-off-by: David Gibson <[email protected]>
> ---
> hw/ppc/spapr.c | 12 ++++++++++--
> 1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index f6e9c2a..7cb167c 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -2376,15 +2376,23 @@ static void spapr_phb_placement(sPAPRMachineState
> *spapr, uint32_t index,
> unsigned n_dma, uint32_t *liobns, Error
> **errp)
> {
> const uint64_t base_buid = 0x800000020000000ULL;
> - const hwaddr phb0_base = 0x10000000000ULL; /* 1 TiB */
> const hwaddr phb_spacing = 0x1000000000ULL; /* 64 GiB */
> const hwaddr mmio_offset = 0xa0000000; /* 2 GiB + 512 MiB */
> const hwaddr pio_offset = 0x80000000; /* 2 GiB */
> const uint32_t max_index = 255;
> + const hwaddr phb0_alignment = 0x10000000000ULL; /* 1 TiB */
>
> - hwaddr phb_base;
> + uint64_t ram_top = MACHINE(spapr)->ram_size;
> + hwaddr phb0_base, phb_base;
> int i;
>
> + if (MACHINE(spapr)->maxram_size > ram_top) {
> + ram_top = spapr->hotplug_memory.base +
> + memory_region_size(&spapr->hotplug_memory.mr);
> + }
Why don't you set directly ram_top to maxram_size?
> +
> + phb0_base = QEMU_ALIGN_UP(ram_top, phb0_alignment);
> +
> if (index > max_index) {
> error_setg(errp, "\"index\" for PAPR PHB is too large (max %u)",
> max_index);
>
Thanks,
Laurent
