Re: [Qemu-devel] [PATCH for-2.12 v3 05/11] spapr: introduce an IRQ allocator using a bitmap

[Greg Kurz <groug@kaod.org>]

On Fri, 10 Nov 2017 15:20:11 +0000
Cédric Le Goater <clg@kaod.org> wrote:

> Let's define a new set of XICSFabric IRQ operations for the latest
> pseries machine. These simply use a a bitmap 'irq_map' as a IRQ number
> allocator.
> 
> The previous pseries machines keep the old set of IRQ operations using
> the ICSIRQState array.
> 
> Signed-off-by: Cédric Le Goater <clg@kaod.org>
> ---
> 
>  Changes since v2 :
> 
>  - introduced a second set of XICSFabric IRQ operations for older
>    pseries machines
> 
>  hw/ppc/spapr.c         | 76 ++++++++++++++++++++++++++++++++++++++++++++++----
>  include/hw/ppc/spapr.h |  3 ++
>  2 files changed, 74 insertions(+), 5 deletions(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 4bdceb45a14f..4ef0b73559ca 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -1681,6 +1681,22 @@ static const VMStateDescription vmstate_spapr_patb_entry = {
>      },
>  };
>  
> +static bool spapr_irq_map_needed(void *opaque)
> +{
> +    return true;

I see that the next patch adds some code to avoid sending the
bitmap if it doesn't contain state, but I guess you should also
explicitly have this function to return false for older machine
types (see remark below).

> +}
> +
> +static const VMStateDescription vmstate_spapr_irq_map = {
> +    .name = "spapr_irq_map",
> +    .version_id = 0,
> +    .minimum_version_id = 0,
> +    .needed = spapr_irq_map_needed,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_BITMAP(irq_map, sPAPRMachineState, 0, nr_irqs),
> +        VMSTATE_END_OF_LIST()
> +    },
> +};
> +
>  static const VMStateDescription vmstate_spapr = {
>      .name = "spapr",
>      .version_id = 3,
> @@ -1700,6 +1716,7 @@ static const VMStateDescription vmstate_spapr = {
>          &vmstate_spapr_ov5_cas,
>          &vmstate_spapr_patb_entry,
>          &vmstate_spapr_pending_events,
> +        &vmstate_spapr_irq_map,
>          NULL
>      }
>  };
> @@ -2337,8 +2354,12 @@ static void ppc_spapr_init(MachineState *machine)
>      /* Setup a load limit for the ramdisk leaving room for SLOF and FDT */
>      load_limit = MIN(spapr->rma_size, RTAS_MAX_ADDR) - FW_OVERHEAD;
>  
> +    /* Initialize the IRQ allocator */
> +    spapr->nr_irqs  = XICS_IRQS_SPAPR;
> +    spapr->irq_map  = bitmap_new(spapr->nr_irqs);
> +

I think you should introduce a sPAPRMachineClass::has_irq_bitmap boolean
so that the bitmap is only allocated for newer machine types. And you should
then use this flag in spapr_irq_map_needed() above.

Apart from that, the rest of the patch looks good.

>      /* Set up Interrupt Controller before we create the VCPUs */
> -    xics_system_init(machine, XICS_IRQS_SPAPR, &error_fatal);
> +    xics_system_init(machine, spapr->nr_irqs, &error_fatal);
>  
>      /* Set up containers for ibm,client-architecture-support negotiated options
>       */
> @@ -3560,7 +3581,7 @@ static int ics_find_free_block(ICSState *ics, int num, int alignnum)
>      return -1;
>  }
>  
> -static bool spapr_irq_test(XICSFabric *xi, int irq)
> +static bool spapr_irq_test_2_11(XICSFabric *xi, int irq)
>  {
>      sPAPRMachineState *spapr = SPAPR_MACHINE(xi);
>      ICSState *ics = spapr->ics;
> @@ -3569,7 +3590,7 @@ static bool spapr_irq_test(XICSFabric *xi, int irq)
>      return !ICS_IRQ_FREE(ics, srcno);
>  }
>  
> -static int spapr_irq_alloc_block(XICSFabric *xi, int count, int align)
> +static int spapr_irq_alloc_block_2_11(XICSFabric *xi, int count, int align)
>  {
>      sPAPRMachineState *spapr = SPAPR_MACHINE(xi);
>      ICSState *ics = spapr->ics;
> @@ -3583,7 +3604,7 @@ static int spapr_irq_alloc_block(XICSFabric *xi, int count, int align)
>      return srcno + ics->offset;
>  }
>  
> -static void spapr_irq_free_block(XICSFabric *xi, int irq, int num)
> +static void spapr_irq_free_block_2_11(XICSFabric *xi, int irq, int num)
>  {
>      sPAPRMachineState *spapr = SPAPR_MACHINE(xi);
>      ICSState *ics = spapr->ics;
> @@ -3601,6 +3622,46 @@ static void spapr_irq_free_block(XICSFabric *xi, int irq, int num)
>      }
>  }
>  
> +static bool spapr_irq_test(XICSFabric *xi, int irq)
> +{
> +    sPAPRMachineState *spapr = SPAPR_MACHINE(xi);
> +    int srcno = irq - spapr->ics->offset;
> +
> +    return test_bit(srcno, spapr->irq_map);
> +}
> +
> +static int spapr_irq_alloc_block(XICSFabric *xi, int count, int align)
> +{
> +    sPAPRMachineState *spapr = SPAPR_MACHINE(xi);
> +    int start = 0;
> +    int srcno;
> +
> +    /*
> +     * The 'align_mask' parameter of bitmap_find_next_zero_area()
> +     * should be one less than a power of 2; 0 means no
> +     * alignment. Adapt the 'align' value of the former allocator to
> +     * fit the requirements of bitmap_find_next_zero_area()
> +     */
> +    align -= 1;
> +
> +    srcno = bitmap_find_next_zero_area(spapr->irq_map, spapr->nr_irqs, start,
> +                                       count, align);
> +    if (srcno == spapr->nr_irqs) {
> +        return -1;
> +    }
> +
> +    bitmap_set(spapr->irq_map, srcno, count);
> +    return srcno + spapr->ics->offset;
> +}
> +
> +static void spapr_irq_free_block(XICSFabric *xi, int irq, int num)
> +{
> +    sPAPRMachineState *spapr = SPAPR_MACHINE(xi);
> +    int srcno = irq - spapr->ics->offset;
> +
> +    bitmap_clear(spapr->irq_map, srcno, num);
> +}
> +
>  static void spapr_pic_print_info(InterruptStatsProvider *obj,
>                                   Monitor *mon)
>  {
> @@ -3778,7 +3839,12 @@ static void spapr_machine_2_11_instance_options(MachineState *machine)
>  
>  static void spapr_machine_2_11_class_options(MachineClass *mc)
>  {
> -    /* Defaults for the latest behaviour inherited from the base class */
> +    XICSFabricClass *xic = XICS_FABRIC_CLASS(mc);
> +
> +    spapr_machine_2_12_class_options(mc);
> +    xic->irq_test = spapr_irq_test_2_11;
> +    xic->irq_alloc_block = spapr_irq_alloc_block_2_11;
> +    xic->irq_free_block = spapr_irq_free_block_2_11;
>  }
>  
>  DEFINE_SPAPR_MACHINE(2_11, "2.11", false);
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index 9d21ca9bde3a..5835c694caff 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -7,6 +7,7 @@
>  #include "hw/ppc/spapr_drc.h"
>  #include "hw/mem/pc-dimm.h"
>  #include "hw/ppc/spapr_ovec.h"
> +#include "qemu/bitmap.h"
>  
>  struct VIOsPAPRBus;
>  struct sPAPRPHBState;
> @@ -78,6 +79,8 @@ struct sPAPRMachineState {
>      struct VIOsPAPRBus *vio_bus;
>      QLIST_HEAD(, sPAPRPHBState) phbs;
>      struct sPAPRNVRAM *nvram;
> +    int32_t nr_irqs;
> +    unsigned long *irq_map;
>      ICSState *ics;
>      sPAPRRTCState rtc;
>