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

[Greg Kurz <groug@kaod.org>]

On Fri, 15 Jun 2018 13:53:03 +0200
Cédric Le Goater <clg@kaod.org> 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 <clg@kaod.org>
> ---
>  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

> +#define SPAPR_IRQ_VIO        0x1040

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.

> +#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)