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

["Cédric Le Goater" <clg@kaod.org>]

Hello,

On 06/15/2018 06:03 PM, Greg Kurz wrote:
> 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.

yes. I am waiting for people to scream : "I want more !"

>> + */
>> +#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 ?

hmm, no. We could have CAPI devices there. remember ? ;)

>> +                                      * by the bitmap allocator */
> 
> The range size is hence 1k (XICS_IRQS_SPAPR) for the time being.

in fact we could this bogus limit and use spapr->irq_map_nr now.

>> +
>> +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.

I think the Error is useless here.


> 
>> +    }
>> +
>>      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 ?

no need. It is redudant with spapr->irq_map which is not allocated in that case.

>> +}
>> +
>> +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.

yes

> 
>> +{
>> +    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 ?

no. one is for the MSI IRQ allocator, the other for the controller. 

> 
>>          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...

yes. but claim() should fail.

Thanks,

C.

>>          }
>>      }
>>  
>> 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)
>