Re: [Qemu-ppc] [PATCH 3/3] spapr: introduce a fixed IRQ number space

[David Gibson]

On Fri, Jun 15, 2018 at 06:03:11PM +0200, Greg Kurz wrote:
> On Fri, 15 Jun 2018 13:53:03 +0200
> Cédric Le Goater <address@hidden> wrote:
> 
> > This proposal introduces a new IRQ number space layout using static
> > numbers for all devices and a bitmap allocator for the MSI numbers
> > which are negotiated by the guest at runtime.
> > 
> > The previous layout is kept in machines raising the 'xics_legacy'
> > flag.
> > 
> > Signed-off-by: Cédric Le Goater <address@hidden>
> > ---
> >  include/hw/ppc/spapr.h     |  4 ++++
> >  include/hw/ppc/spapr_irq.h | 30 ++++++++++++++++++++++++
> >  hw/ppc/spapr.c             | 31 +++++++++++++++++++++++++
> >  hw/ppc/spapr_events.c      | 12 ++++++++--
> >  hw/ppc/spapr_irq.c         | 57 
> > ++++++++++++++++++++++++++++++++++++++++++++++
> >  hw/ppc/spapr_pci.c         | 28 ++++++++++++++++++-----
> >  hw/ppc/spapr_vio.c         | 15 ++++++++----
> >  hw/ppc/Makefile.objs       |  2 +-
> >  8 files changed, 166 insertions(+), 13 deletions(-)
> >  create mode 100644 include/hw/ppc/spapr_irq.h
> >  create mode 100644 hw/ppc/spapr_irq.c
> > 
> > diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> > index 49cda04b1493..094c7780130e 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 "hw/ppc/spapr_irq.h"
> >  
> >  struct VIOsPAPRBus;
> >  struct sPAPRPHBState;
> > @@ -164,6 +165,9 @@ struct sPAPRMachineState {
> >      char *kvm_type;
> >  
> >      const char *icp_type;
> > +    bool xics_legacy;
> > +    int32_t irq_map_nr;
> > +    unsigned long *irq_map;
> >  
> >      bool cmd_line_caps[SPAPR_CAP_NUM];
> >      sPAPRCapabilities def, eff, mig;
> > diff --git a/include/hw/ppc/spapr_irq.h b/include/hw/ppc/spapr_irq.h
> > new file mode 100644
> > index 000000000000..07e36d1c7e74
> > --- /dev/null
> > +++ b/include/hw/ppc/spapr_irq.h
> > @@ -0,0 +1,30 @@
> > +/*
> > + * QEMU PowerPC sPAPR IRQ backend definitions
> > + *
> > + * Copyright (c) 2018, IBM Corporation.
> > + *
> > + * This code is licensed under the GPL version 2 or later. See the
> > + * COPYING file in the top-level directory.
> > + */
> > +#ifndef HW_SPAPR_IRQ_H
> > +#define HW_SPAPR_IRQ_H
> > +
> > +/*
> > + * IRQ ranges per type
> 
> Well, range offsets actually. Maybe you could document the range size
> as well for each type.
> 
> > + */
> > +#define SPAPR_IRQ_EPOW       0x1000  /* XICS_IRQ_BASE offset */
> > +#define SPAPR_IRQ_HOTPLUG    0x1001
> 
> This is just 1 irq, ie, range 0x1002-0x103F is unused

I'm good with that.  I'm thinking of that as the reserved range for
any more "one off" interrupts we get.

> > +#define SPAPR_IRQ_VIO        0x1040

I'd bump it up to 0x1100, makes for rounder numbers.  We can up the
total limit if we have to.

> This is 1 irq per device, hence up to 64 devices
> 
> > +#define SPAPR_IRQ_PCI_LSI    0x1080
> > +
> 
> This is 4 irqs per PHB, hence up to 32 PHBs. Cool, we're currently
> limited to 31 PHBs.

Likewise I'd suggest spacing out this range.  Rearranging all the irqs
would probably be more trouble than raising the #PHBs limit at this
point.  Well.. maybe.  Raising the PHBs limit does already involve
moving a bunch of address space blocks around.

> > +#define SPAPR_IRQ_MSI        0x1100  /* Offset of the dynamic range covered
> 
> We only support dynamic MSIs with PCI, maybe rename to SPAPR_IRQ_PCI_MSI ?
> 
> > +                                      * by the bitmap allocator */
> 
> The range size is hence 1k (XICS_IRQS_SPAPR) for the time being.
> 
> > +
> > +void spapr_irq_msi_init(sPAPRMachineState *spapr, uint32_t nr_irqs,
> > +                       Error **errp);
>                          ^
>                      missing space
> 
> > +int spapr_irq_msi_alloc(sPAPRMachineState *spapr, uint32_t num, bool align,
> > +                        Error **errp);
> > +void spapr_irq_msi_free(sPAPRMachineState *spapr, int irq, uint32_t num);
> > +void spapr_irq_msi_reset(sPAPRMachineState *spapr);
> > +
> > +#endif
> > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > index c464951747e3..32aa5d869d9c 100644
> > --- a/hw/ppc/spapr.c
> > +++ b/hw/ppc/spapr.c
> > @@ -187,6 +187,11 @@ static void xics_system_init(MachineState *machine, 
> > int nr_irqs, Error **errp)
> >  {
> >      sPAPRMachineState *spapr = SPAPR_MACHINE(machine);
> >  
> > +    /* Initialize the MSI IRQ allocator. */
> > +    if (!spapr->xics_legacy) {
> > +        spapr_irq_msi_init(spapr, nr_irqs, &error_fatal);
> 
> The error should be propagated to the caller.
> 
> > +    }
> > +
> >      if (kvm_enabled()) {
> >          if (machine_kernel_irqchip_allowed(machine) &&
> >              !xics_kvm_init(spapr, errp)) {
> 
> And I now realize that the way errors are handled here is badly
> broken.
> 
> In the default case, this function is supposed to try in-kernel XICS
> first and if it fails, then fallback to userland XICS. But since we
> pass errp down to xics_kvm_init() and the caller happens to pass
> &error_fatal, we stop right here instead of trying the fallback.
> 
> And if the caller changes to pass a standard &local_err instead,
> things would be even worse. With the same scenario, QEMU would
> probably exit if it could fallback to the userland XICS, or abort
> otherwise because error_set() would be called with an already set
> *errp.
> 
> Since this beha^wug is mine (commit 3d85885a1b1f3), let me fix it
> first :)
> 
> > @@ -1629,6 +1634,10 @@ static void spapr_machine_reset(void)
> >          ppc_set_compat(first_ppc_cpu, spapr->max_compat_pvr, &error_fatal);
> >      }
> >  
> > +    if (!spapr->xics_legacy) {
> > +        spapr_irq_msi_reset(spapr);
> > +    }
> > +
> >      qemu_devices_reset();
> >  
> >      /* DRC reset may cause a device to be unplugged. This will cause 
> > troubles
> > @@ -1903,6 +1912,24 @@ static const VMStateDescription 
> > vmstate_spapr_patb_entry = {
> >      },
> >  };
> >  
> > +static bool spapr_irq_map_needed(void *opaque)
> > +{
> > +    sPAPRMachineState *spapr = opaque;
> > +
> > +    return spapr->irq_map && !bitmap_empty(spapr->irq_map, 
> > spapr->irq_map_nr);
> 
> Maybe check !spapr->xics_legacy as well to preserve backward migration
> to older machines ?
> 
> > +}
> > +
> > +static const VMStateDescription vmstate_spapr_irq_map = {
> > +    .name = "spapr_irq_map",
> > +    .version_id = 1,
> > +    .minimum_version_id = 1,
> > +    .needed = spapr_irq_map_needed,
> > +    .fields = (VMStateField[]) {
> > +        VMSTATE_BITMAP(irq_map, sPAPRMachineState, 0, irq_map_nr),
> > +        VMSTATE_END_OF_LIST()
> > +    },
> > +};
> > +
> >  static const VMStateDescription vmstate_spapr = {
> >      .name = "spapr",
> >      .version_id = 3,
> > @@ -1930,6 +1957,7 @@ static const VMStateDescription vmstate_spapr = {
> >          &vmstate_spapr_cap_cfpc,
> >          &vmstate_spapr_cap_sbbc,
> >          &vmstate_spapr_cap_ibs,
> > +        &vmstate_spapr_irq_map,
> >          NULL
> >      }
> >  };
> > @@ -4101,7 +4129,10 @@ DEFINE_SPAPR_MACHINE(3_0, "3.0", true);
> >  
> >  static void spapr_machine_2_12_instance_options(MachineState *machine)
> >  {
> > +    sPAPRMachineState *spapr = SPAPR_MACHINE(machine);
> > +
> >      spapr_machine_3_0_instance_options(machine);
> > +    spapr->xics_legacy = true;
> >  }
> >  
> >  static void spapr_machine_2_12_class_options(MachineClass *mc)
> > diff --git a/hw/ppc/spapr_events.c b/hw/ppc/spapr_events.c
> > index 3b6ae7272092..1ef7ce7f1509 100644
> > --- a/hw/ppc/spapr_events.c
> > +++ b/hw/ppc/spapr_events.c
> > @@ -709,7 +709,11 @@ void spapr_events_init(sPAPRMachineState *spapr)
> >  {
> >      int epow_irq;
> >  
> > -    epow_irq = spapr_irq_findone(spapr, &error_fatal);
> > +    if (spapr->xics_legacy) {
> > +        epow_irq = spapr_irq_findone(spapr, &error_fatal);
> > +    } else {
> > +        epow_irq = SPAPR_IRQ_EPOW;
> > +    }
> >  
> >      spapr_irq_claim(spapr, epow_irq, 1, false, &error_fatal);
> >  
> > @@ -731,7 +735,11 @@ void spapr_events_init(sPAPRMachineState *spapr)
> >      if (spapr->use_hotplug_event_source) {
> >          int hp_irq;
> >  
> > -        hp_irq = spapr_irq_findone(spapr, &error_fatal);
> > +        if (spapr->xics_legacy) {
> > +            hp_irq = spapr_irq_findone(spapr, &error_fatal);
> > +        } else {
> > +            hp_irq = SPAPR_IRQ_HOTPLUG;
> > +        }
> >  
> >          spapr_irq_claim(spapr, hp_irq, 1, false, &error_fatal);
> >  
> > diff --git a/hw/ppc/spapr_irq.c b/hw/ppc/spapr_irq.c
> > new file mode 100644
> > index 000000000000..55fa764c85d1
> > --- /dev/null
> > +++ b/hw/ppc/spapr_irq.c
> > @@ -0,0 +1,57 @@
> > +/*
> > + * QEMU PowerPC sPAPR IRQ interface
> > + *
> > + * Copyright (c) 2018, IBM Corporation.
> > + *
> > + * This code is licensed under the GPL version 2 or later. See the
> > + * COPYING file in the top-level directory.
> > + */
> > +
> > +#include "qemu/osdep.h"
> > +#include "qemu/log.h"
> > +#include "qemu/error-report.h"
> > +#include "qapi/error.h"
> > +#include "hw/ppc/spapr.h"
> > +#include "hw/ppc/xics.h"
> > +
> > +void spapr_irq_msi_init(sPAPRMachineState *spapr, uint32_t nr_irqs,
> > +                        Error **errp)
> 
> What's the errp for ? It looks like this function can never return
> an error. Maybe just drop it.
> 
> > +{
> > +    spapr->irq_map_nr = XICS_IRQ_BASE + nr_irqs - SPAPR_IRQ_MSI;
> > +    spapr->irq_map = bitmap_new(spapr->irq_map_nr);
> > +}
> > +
> > +int spapr_irq_msi_alloc(sPAPRMachineState *spapr, uint32_t num, bool align,
> > +                        Error **errp)
> > +{
> > +    int irq;
> > +
> > +    /*
> > +     * 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;
> > +
> > +    irq = bitmap_find_next_zero_area(spapr->irq_map, spapr->irq_map_nr, 0, 
> > num,
> > +                                     align);
> > +    if (irq == spapr->irq_map_nr) {
> > +        error_setg(errp, "can't find a free %d-IRQ block", num);
> > +        return -1;
> > +    }
> > +
> > +    bitmap_set(spapr->irq_map, irq, num);
> > +
> > +    return irq + SPAPR_IRQ_MSI;
> > +}
> > +
> > +void spapr_irq_msi_free(sPAPRMachineState *spapr, int irq, uint32_t num)
> > +{
> > +    bitmap_clear(spapr->irq_map, irq - SPAPR_IRQ_MSI, num);
> > +}
> > +
> > +void spapr_irq_msi_reset(sPAPRMachineState *spapr)
> > +{
> > +    bitmap_clear(spapr->irq_map, 0, spapr->irq_map_nr);
> > +}
> > diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
> > index 7394c62b4a8b..f3c4a25fb482 100644
> > --- a/hw/ppc/spapr_pci.c
> > +++ b/hw/ppc/spapr_pci.c
> > @@ -333,6 +333,9 @@ static void rtas_ibm_change_msi(PowerPCCPU *cpu, 
> > sPAPRMachineState *spapr,
> >              return;
> >          }
> >  
> > +        if (!spapr->xics_legacy) {
> > +            spapr_irq_msi_free(spapr, msi->first_irq, msi->num);
> > +        }
> >          spapr_irq_free(spapr, msi->first_irq, msi->num);
> 
> Shouldn't ^^ be in an else block ?
> 
> >          if (msi_present(pdev)) {
> >              spapr_msi_setmsg(pdev, 0, false, 0, 0);
> > @@ -371,7 +374,13 @@ static void rtas_ibm_change_msi(PowerPCCPU *cpu, 
> > sPAPRMachineState *spapr,
> >      }
> >  
> >      /* Allocate MSIs */
> > -    irq = spapr_irq_find(spapr, req_num, ret_intr_type == RTAS_TYPE_MSI, 
> > &err);
> > +    if (spapr->xics_legacy) {
> > +        irq = spapr_irq_find(spapr, req_num, ret_intr_type == 
> > RTAS_TYPE_MSI,
> > +                             &err);
> > +    } else {
> > +        irq = spapr_irq_msi_alloc(spapr, req_num,
> > +                                  ret_intr_type == RTAS_TYPE_MSI, &err);
> > +    }
> >      if (err) {
> >          error_reportf_err(err, "Can't allocate MSIs for device %x: ",
> >                            config_addr);
> > @@ -388,6 +397,9 @@ static void rtas_ibm_change_msi(PowerPCCPU *cpu, 
> > sPAPRMachineState *spapr,
> >  
> >      /* Release previous MSIs */
> >      if (msi) {
> > +        if (!spapr->xics_legacy) {
> > +            spapr_irq_msi_free(spapr, msi->first_irq, msi->num);
> > +        }
> >          spapr_irq_free(spapr, msi->first_irq, msi->num);
> >          g_hash_table_remove(phb->msi, &config_addr);
> >      }
> > @@ -1704,11 +1716,15 @@ static void spapr_phb_realize(DeviceState *dev, 
> > Error **errp)
> >          uint32_t irq;
> >          Error *local_err = NULL;
> >  
> > -        irq = spapr_irq_findone(spapr, &local_err);
> > -        if (local_err) {
> > -            error_propagate(errp, local_err);
> > -            error_prepend(errp, "can't allocate LSIs: ");
> > -            return;
> > +        if (spapr->xics_legacy) {
> > +            irq = spapr_irq_findone(spapr, &local_err);
> > +            if (local_err) {
> > +                error_propagate(errp, local_err);
> > +                error_prepend(errp, "can't allocate LSIs: ");
> > +                return;
> > +            }
> > +        } else {
> > +            irq = SPAPR_IRQ_PCI_LSI + sphb->index * PCI_NUM_PINS + i;
> >          }
> >  
> >          spapr_irq_claim(spapr, irq, 1, true, &local_err);
> > diff --git a/hw/ppc/spapr_vio.c b/hw/ppc/spapr_vio.c
> > index ad9b56e28447..7707bda6a38d 100644
> > --- a/hw/ppc/spapr_vio.c
> > +++ b/hw/ppc/spapr_vio.c
> > @@ -436,6 +436,9 @@ static void spapr_vio_busdev_reset(DeviceState *qdev)
> >      }
> >  }
> >  
> > +/* TODO : poor VIO device indexing ... */
> > +static uint32_t vio_index;
> > +
> >  static void spapr_vio_busdev_realize(DeviceState *qdev, Error **errp)
> >  {
> >      sPAPRMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
> > @@ -476,10 +479,14 @@ static void spapr_vio_busdev_realize(DeviceState 
> > *qdev, Error **errp)
> >      }
> >  
> >      if (!dev->irq) {
> > -        dev->irq = spapr_irq_findone(spapr, &local_err);
> > -        if (local_err) {
> > -            error_propagate(errp, local_err);
> > -            return;
> > +        if (spapr->xics_legacy) {
> > +            dev->irq = spapr_irq_findone(spapr, &local_err);
> > +            if (local_err) {
> > +                error_propagate(errp, local_err);
> > +                return;
> > +            }
> > +        } else {
> > +            dev->irq = SPAPR_IRQ_VIO + vio_index++;
> 
> This can overlap the next range if we have more than 64 VIO devices...
> 
> >          }
> >      }
> >  
> > diff --git a/hw/ppc/Makefile.objs b/hw/ppc/Makefile.objs
> > index 86d82a6ec3ac..4fe3b7804d43 100644
> > --- a/hw/ppc/Makefile.objs
> > +++ b/hw/ppc/Makefile.objs
> > @@ -4,7 +4,7 @@ obj-y += ppc.o ppc_booke.o fdt.o
> >  obj-$(CONFIG_PSERIES) += spapr.o spapr_caps.o spapr_vio.o spapr_events.o
> >  obj-$(CONFIG_PSERIES) += spapr_hcall.o spapr_iommu.o spapr_rtas.o
> >  obj-$(CONFIG_PSERIES) += spapr_pci.o spapr_rtc.o spapr_drc.o spapr_rng.o
> > -obj-$(CONFIG_PSERIES) += spapr_cpu_core.o spapr_ovec.o
> > +obj-$(CONFIG_PSERIES) += spapr_cpu_core.o spapr_ovec.o spapr_irq.o
> >  # IBM PowerNV
> >  obj-$(CONFIG_POWERNV) += pnv.o pnv_xscom.o pnv_core.o pnv_lpc.o pnv_psi.o 
> > pnv_occ.o pnv_bmc.o
> >  ifeq ($(CONFIG_PCI)$(CONFIG_PSERIES)$(CONFIG_LINUX), yyy)
> 

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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