Re: [Qemu-devel] [RFC v2 5/7] hw/arm/virt: GICv3 DT node with one or two redistributor regions

[Peter Maydell]

On 13 May 2018 at 15:35, Eric Auger <address@hidden> wrote:
> This patch allows the creation of a GICv3 node with 1 or 2
> redistributor regions depending on the number of smu_cpus.
> The second redistributor region is located just after the
> existing RAM region, at 256GB and contains up to (512 - 123) vcpus.
>
> Please refer to kernel documentation for further node details:
> Documentation/devicetree/bindings/interrupt-controller/arm,gic-v3.txt
>
> Signed-off-by: Eric Auger <address@hidden>
> ---
>  hw/arm/virt.c         | 29 ++++++++++++++++++++++++-----
>  include/hw/arm/virt.h | 12 ++++++++++++
>  2 files changed, 36 insertions(+), 5 deletions(-)
>
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index c9d842d..f35962a 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -151,6 +151,8 @@ static const MemMapEntry a15memmap[] = {
>      [VIRT_PCIE_PIO] =           { 0x3eff0000, 0x00010000 },
>      [VIRT_PCIE_ECAM] =          { 0x3f000000, 0x01000000 },
>      [VIRT_MEM] =                { 0x40000000, RAMLIMIT_BYTES },
> +    /* Allows 512 - 123 additional vcpus (each 2x64kB) */
> +    [VIRT_GIC_REDIST2] =        { 0x4000000000ULL, 0x30A0000LL },

This is a weird size.

>      /* Second PCIe window, 512GB wide at the 512GB boundary */
>      [VIRT_PCIE_MMIO_HIGH] =   { 0x8000000000ULL, 0x8000000000ULL },
>  };
> @@ -404,13 +406,30 @@ static void fdt_add_gic_node(VirtMachineState *vms)
>      qemu_fdt_setprop_cell(vms->fdt, "/intc", "#size-cells", 0x2);
>      qemu_fdt_setprop(vms->fdt, "/intc", "ranges", NULL, 0);
>      if (vms->gic_version == 3) {
> +        int nb_redist_regions = virt_gicv3_redist_region_count(vms);
> +
>          qemu_fdt_setprop_string(vms->fdt, "/intc", "compatible",
>                                  "arm,gic-v3");
> -        qemu_fdt_setprop_sized_cells(vms->fdt, "/intc", "reg",
> -                                     2, vms->memmap[VIRT_GIC_DIST].base,
> -                                     2, vms->memmap[VIRT_GIC_DIST].size,
> -                                     2, vms->memmap[VIRT_GIC_REDIST].base,
> -                                     2, vms->memmap[VIRT_GIC_REDIST].size);
> +
> +        qemu_fdt_setprop_cell(vms->fdt, "/intc",
> +                              "#redistributor-regions", nb_redist_regions);
> +
> +        if (nb_redist_regions == 1) {
> +            qemu_fdt_setprop_sized_cells(vms->fdt, "/intc", "reg",
> +                                         2, vms->memmap[VIRT_GIC_DIST].base,
> +                                         2, vms->memmap[VIRT_GIC_DIST].size,
> +                                         2, 
> vms->memmap[VIRT_GIC_REDIST].base,
> +                                         2, 
> vms->memmap[VIRT_GIC_REDIST].size);
> +        } else {
> +            qemu_fdt_setprop_sized_cells(vms->fdt, "/intc", "reg",
> +                                         2, vms->memmap[VIRT_GIC_DIST].base,
> +                                         2, vms->memmap[VIRT_GIC_DIST].size,
> +                                         2, 
> vms->memmap[VIRT_GIC_REDIST].base,
> +                                         2, 
> vms->memmap[VIRT_GIC_REDIST].size,
> +                                         2, 
> vms->memmap[VIRT_GIC_REDIST2].base,
> +                                         2, 
> vms->memmap[VIRT_GIC_REDIST2].size);
> +        }
> +
>          if (vms->virt) {
>              qemu_fdt_setprop_cells(vms->fdt, "/intc", "interrupts",
>                                     GIC_FDT_IRQ_TYPE_PPI, 
> ARCH_GICV3_MAINT_IRQ,
> diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h
> index 886372c..ba52716 100644
> --- a/include/hw/arm/virt.h
> +++ b/include/hw/arm/virt.h
> @@ -35,6 +35,7 @@
>  #include "qemu/notify.h"
>  #include "hw/boards.h"
>  #include "hw/arm/arm.h"
> +#include "sysemu/kvm.h"
>
>  #define NUM_GICV2M_SPIS       64
>  #define NUM_VIRTIO_TRANSPORTS 32
> @@ -60,6 +61,7 @@ enum {
>      VIRT_GIC_V2M,
>      VIRT_GIC_ITS,
>      VIRT_GIC_REDIST,
> +    VIRT_GIC_REDIST2,
>      VIRT_SMMU,
>      VIRT_UART,
>      VIRT_MMIO,
> @@ -129,4 +131,14 @@ typedef struct {
>
>  void virt_acpi_setup(VirtMachineState *vms);
>
> +/* Return the number of used redistributor regions  */
> +static inline int virt_gicv3_redist_region_count(VirtMachineState *vms)
> +{
> +    uint32_t rdist1_count = vms->memmap[VIRT_GIC_REDIST].size / 0x20000;
> +
> +    assert(vms->gic_version == 3);
> +
> +    return kvm_irqchip_in_kernel() && vms->smp_cpus > rdist1_count ? 2 : 1;

Why does kvm_irqchip_in_kernel() matter here? If we have more CPUs than
we can fit in the first region, we need 2 regardless. If we're using
the TCG GICv3 then hopefully we'll bail out with a useful error
message when we try to create multiple redistributor regions for it
(until we add support for that).

> +}

I notice there's a lot of 0x20000 constants floating about in this
patch set; could we use a suitable #define ?

thanks
-- PMM