Re: [Qemu-devel] [PATCH 1/8] spapr: introduce an IRQ allocator at the machine level

[Greg Kurz <groug@kaod.org>]

On Sun, 29 Oct 2017 19:12:10 +0100
Cédric Le Goater <clg@kaod.org> wrote:

> Currently, the ICSState 'ics' object of the sPAPR machine acts as the
> global interrupt source handler and also as the IRQ number allocator
> for the machine. Some IRQ numbers are allocated very early in the
> machine initialization sequence to populate the device tree, and this
> is a problem to introduce the new POWER XIVE interrupt model, as it
> needs to share the IRQ numbers with the older model.
> 
> To prepare ground for XIVE, here is a proposal adding a set of new
> XICSFabric operations to let the machine handle directly the IRQ
> number allocation and to decorrelate the allocation from the interrupt
> source object :
> 
>     bool (*irq_test)(XICSFabric *xi, int irq);
>     int (*irq_alloc_block)(XICSFabric *xi, int count, int align);
>     void (*irq_free_block)(XICSFabric *xi, int irq, int num);
> 
> In these prototypes, the 'irq' parameter refers to a number in the
> global IRQ number space. Indexes for arrays storing different state
> informations on the interrupts, like the ICSIRQState, are named
> 'srcno'.
> 
> On the sPAPR platform, these IRQ operations are simply backed by a
> bitmap 'irq_map' in the machine.
> 
> 'irq_base' is a base number in sync with the ICSState 'offset'. It
> lets us allocate only the subset of the IRQ numbers used on the sPAPR
> platform but we could also choose to waste some extra bytes (512) and
> allocate the whole number space. 'nr_irqs' is the total number of
> IRQs, required to manipulate the bitmap.
> 
> Signed-off-by: Cédric Le Goater <clg@kaod.org>
> ---

Hi,

The idea makes sense but this patch brings too many changes IMHO.

>  hw/intc/xics.c         |  3 ++-
>  hw/intc/xics_spapr.c   | 57 ++++++++++++----------------------------------
>  hw/ppc/spapr.c         | 62 +++++++++++++++++++++++++++++++++++++++++++++++++-
>  include/hw/ppc/spapr.h |  4 ++++
>  include/hw/ppc/xics.h  |  4 ++++
>  5 files changed, 85 insertions(+), 45 deletions(-)
> 
> diff --git a/hw/intc/xics.c b/hw/intc/xics.c
> index cc9816e7f204..2c4899f278e2 100644
> --- a/hw/intc/xics.c
> +++ b/hw/intc/xics.c
> @@ -53,6 +53,7 @@ void icp_pic_print_info(ICPState *icp, Monitor *mon)
>  void ics_pic_print_info(ICSState *ics, Monitor *mon)
>  {
>      uint32_t i;
> +    XICSFabricClass *xic = XICS_FABRIC_GET_CLASS(ics->xics);
>  
>      monitor_printf(mon, "ICS %4x..%4x %p\n",
>                     ics->offset, ics->offset + ics->nr_irqs - 1, ics);
> @@ -64,7 +65,7 @@ void ics_pic_print_info(ICSState *ics, Monitor *mon)
>      for (i = 0; i < ics->nr_irqs; i++) {
>          ICSIRQState *irq = ics->irqs + i;
>  
> -        if (!(irq->flags & XICS_FLAGS_IRQ_MASK)) {
> +        if (!xic->irq_test(ics->xics, i + ics->offset)) {
>              continue;
>          }
>          monitor_printf(mon, "  %4x %s %02x %02x\n",
> diff --git a/hw/intc/xics_spapr.c b/hw/intc/xics_spapr.c
> index d98ea8b13068..f2e20bca5b2e 100644
> --- a/hw/intc/xics_spapr.c
> +++ b/hw/intc/xics_spapr.c
> @@ -245,50 +245,23 @@ void xics_spapr_init(sPAPRMachineState *spapr)
>      spapr_register_hypercall(H_IPOLL, h_ipoll);
>  }
>  
> -#define ICS_IRQ_FREE(ics, srcno)   \
> -    (!((ics)->irqs[(srcno)].flags & (XICS_FLAGS_IRQ_MASK)))
> -
> -static int ics_find_free_block(ICSState *ics, int num, int alignnum)
> -{
> -    int first, i;
> -
> -    for (first = 0; first < ics->nr_irqs; first += alignnum) {
> -        if (num > (ics->nr_irqs - first)) {
> -            return -1;
> -        }
> -        for (i = first; i < first + num; ++i) {
> -            if (!ICS_IRQ_FREE(ics, i)) {
> -                break;
> -            }
> -        }
> -        if (i == (first + num)) {
> -            return first;
> -        }
> -    }
> -
> -    return -1;
> -}
> -
>  int spapr_ics_alloc(ICSState *ics, int irq_hint, bool lsi, Error **errp)
>  {
>      int irq;
> +    XICSFabricClass *xic = XICS_FABRIC_GET_CLASS(ics->xics);
>  
> -    if (!ics) {
> -        return -1;
> -    }

If spapr_ics_alloc() is never called with ics == NULL, then you
should assert. Also, this looks like this deserves a separate
patch.

>      if (irq_hint) {
> -        if (!ICS_IRQ_FREE(ics, irq_hint - ics->offset)) {
> +        if (xic->irq_test(ics->xics, irq_hint)) {
>              error_setg(errp, "can't allocate IRQ %d: already in use", irq_hint);
>              return -1;
>          }
>          irq = irq_hint;
>      } else {
> -        irq = ics_find_free_block(ics, 1, 1);
> +        irq = xic->irq_alloc_block(ics->xics, 1, 0);
>          if (irq < 0) {
>              error_setg(errp, "can't allocate IRQ: no IRQ left");
>              return -1;
>          }
> -        irq += ics->offset;
>      }
>  
>      ics_set_irq_type(ics, irq - ics->offset, lsi);
> @@ -305,10 +278,8 @@ int spapr_ics_alloc_block(ICSState *ics, int num, bool lsi,
>                            bool align, Error **errp)
>  {
>      int i, first = -1;
> +    XICSFabricClass *xic = XICS_FABRIC_GET_CLASS(ics->xics);
>  
> -    if (!ics) {
> -        return -1;
> -    }
>  

Ditto.

>      /*
>       * MSIMesage::data is used for storing VIRQ so
> @@ -320,9 +291,9 @@ int spapr_ics_alloc_block(ICSState *ics, int num, bool lsi,
>      if (align) {
>          assert((num == 1) || (num == 2) || (num == 4) ||
>                 (num == 8) || (num == 16) || (num == 32));
> -        first = ics_find_free_block(ics, num, num);
> +        first = xic->irq_alloc_block(ics->xics, num, num);
>      } else {
> -        first = ics_find_free_block(ics, num, 1);
> +        first = xic->irq_alloc_block(ics->xics, num, 0);
>      }
>      if (first < 0) {
>          error_setg(errp, "can't find a free %d-IRQ block", num);
> @@ -331,25 +302,25 @@ int spapr_ics_alloc_block(ICSState *ics, int num, bool lsi,
>  
>      if (first >= 0) {

It looks like this check isn't needed since we return in the first < 0 case.
Maybe you can fix this in a preliminary patch ?

>          for (i = first; i < first + num; ++i) {
> -            ics_set_irq_type(ics, i, lsi);
> +            ics_set_irq_type(ics, i - ics->offset, lsi);
>          }
>      }
> -    first += ics->offset;
>  
>      trace_xics_alloc_block(first, num, lsi, align);
>  
>      return first;
>  }
>  
> -static void ics_free(ICSState *ics, int srcno, int num)
> +static void ics_free(ICSState *ics, int irq, int num)
>  {
>      int i;
> +    XICSFabricClass *xic = XICS_FABRIC_GET_CLASS(ics->xics);
>  
> -    for (i = srcno; i < srcno + num; ++i) {
> -        if (ICS_IRQ_FREE(ics, i)) {
> -            trace_xics_ics_free_warn(0, i + ics->offset);
> +    for (i = irq; i < irq + num; ++i) {
> +        if (xic->irq_test(ics->xics, i)) {
> +            trace_xics_ics_free_warn(0, i);
>          }
> -        memset(&ics->irqs[i], 0, sizeof(ICSIRQState));
> +        xic->irq_free_block(ics->xics, i, 1);
>      }
>  }
>  
> @@ -357,7 +328,7 @@ void spapr_ics_free(ICSState *ics, int irq, int num)
>  {
>      if (ics_valid_irq(ics, irq)) {
>          trace_xics_ics_free(0, irq, num);
> -        ics_free(ics, irq - ics->offset, num);
> +        ics_free(ics, irq, num);
>      }
>  }
>  
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index d682f013d422..88da4bad2328 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -1681,6 +1681,24 @@ static const VMStateDescription vmstate_spapr_patb_entry = {
>      },
>  };
>  
> +static bool spapr_irq_map_needed(void *opaque)
> +{
> +    sPAPRMachineState *spapr = opaque;
> +
> +    return find_first_bit(spapr->irq_map, spapr->nr_irqs) < spapr->nr_irqs;
> +}

This will allow migration from older QEMU. Maybe you can add a machine property
so that the subsection is only generated for newer pseries, and you'll support
migration to older QEMU (see details at the end of === Subsections === in
docs/devel/migration.txt).

> +
> +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 +1718,7 @@ static const VMStateDescription vmstate_spapr = {
>          &vmstate_spapr_ov5_cas,
>          &vmstate_spapr_patb_entry,
>          &vmstate_spapr_pending_events,
> +        &vmstate_spapr_irq_map,
>          NULL
>      }
>  };
> @@ -2337,8 +2356,13 @@ 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);
> +    spapr->irq_base = XICS_IRQ_BASE;
> +
>      /* 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
>       */
> @@ -3536,6 +3560,38 @@ static ICPState *spapr_icp_get(XICSFabric *xi, int vcpu_id)
>      return cpu ? ICP(cpu->intc) : NULL;
>  }
>  
> +static bool spapr_irq_test(XICSFabric *xi, int irq)
> +{
> +    sPAPRMachineState *spapr = SPAPR_MACHINE(xi);
> +    int srcno = irq - spapr->irq_base;
> +
> +    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;
> +
> +    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->irq_base;
> +}
> +
> +static void spapr_irq_free_block(XICSFabric *xi, int irq, int num)
> +{
> +    sPAPRMachineState *spapr = SPAPR_MACHINE(xi);
> +    int srcno = irq - spapr->irq_base;
> +
> +    bitmap_clear(spapr->irq_map, srcno, num);
> +}
> +
>  static void spapr_pic_print_info(InterruptStatsProvider *obj,
>                                   Monitor *mon)
>  {
> @@ -3630,6 +3686,10 @@ static void spapr_machine_class_init(ObjectClass *oc, void *data)
>      xic->ics_get = spapr_ics_get;
>      xic->ics_resend = spapr_ics_resend;
>      xic->icp_get = spapr_icp_get;
> +    xic->irq_test = spapr_irq_test;
> +    xic->irq_alloc_block = spapr_irq_alloc_block;
> +    xic->irq_free_block = spapr_irq_free_block;
> +
>      ispc->print_info = spapr_pic_print_info;
>      /* Force NUMA node memory size to be a multiple of
>       * SPAPR_MEMORY_BLOCK_SIZE (256M) since that's the granularity
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index 9d21ca9bde3a..b962bfe09bb5 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 +79,9 @@ struct sPAPRMachineState {
>      struct VIOsPAPRBus *vio_bus;
>      QLIST_HEAD(, sPAPRPHBState) phbs;
>      struct sPAPRNVRAM *nvram;
> +    int32_t nr_irqs;
> +    unsigned long *irq_map;
> +    uint32_t irq_base;
>      ICSState *ics;
>      sPAPRRTCState rtc;
>  
> diff --git a/include/hw/ppc/xics.h b/include/hw/ppc/xics.h
> index 28d248abad61..30e7f2e0a7dd 100644
> --- a/include/hw/ppc/xics.h
> +++ b/include/hw/ppc/xics.h
> @@ -175,6 +175,10 @@ typedef struct XICSFabricClass {
>      ICSState *(*ics_get)(XICSFabric *xi, int irq);
>      void (*ics_resend)(XICSFabric *xi);
>      ICPState *(*icp_get)(XICSFabric *xi, int server);
> +    /* IRQ allocator helpers */
> +    bool (*irq_test)(XICSFabric *xi, int irq);
> +    int (*irq_alloc_block)(XICSFabric *xi, int count, int align);
> +    void (*irq_free_block)(XICSFabric *xi, int irq, int num);

API looks good to me. I suggest you introduce it in a dedicated patch, and
change the allocator implementation in another patch.

>  } XICSFabricClass;
>  
>  #define XICS_IRQS_SPAPR               1024