Re: [Qemu-devel] [PATCH v2 03/19] spapr: introduce the XIVE interrupt sources

[David Gibson]

On Sat, Dec 09, 2017 at 09:43:22AM +0100, Cédric Le Goater wrote:
> Each XIVE interrupt source is associated with a two bit state machine
> called an Event State Buffer (ESB) : the first bit "P" means that an
> interrupt is "pending" and waiting for an EOI and the bit "Q" (queued)
> means a new interrupt was triggered while another was still pending.
> 
> When an event is triggered, the associated interrupt state bits are
> fetched and modified and forwarded to the virtualization engine of the
> controller doing the routing. These can also be controlled by MMIO, to
> trigger events or turn off the sources for instance. See code for more
> details on the states and transitions.
> 
> The MMIO space for the ESBs is 512GB large on the bare-metal system
> (PowerNV) and the BAR depends on the chip id. In our model for the
> sPAPR machine, we choose to only map the sub-region for the
> provisioned IRQ numbers and to use the mapping address of chip 0 of a
> real system.

I think we probably want a device property to make the virtualized
base address arbitrary.  It's fine for it to default to the chip 0
base, but that'll make it easier to adapt if we need to later on.

As noted in the followup messages, I think you're going to want to
move this stuff from the current xive object into a "block of sources"
object.

Apart from that this looks pretty sound.

> In the real world, each source may have different characteristics
> depending on the revision of a controller or the CPU. Early systems
> had two different MMIO pages for trigger and for EOI. We choose to use
> the same characteristics for all sources to simplify the model. The
> minimum CPU level for XIVE exploitation mode will be DD2.X as it has
> full support.
> 
> The OS will obtain the address of the MMIO page of the ESB entry
> associated with a source and its characteristic using the
> H_INT_GET_SOURCE_INFO hcall. This will be addressed in the patch
> introducing the hcalls.
> 
> The spapr_xive_irq() routine in charge of triggering the CPU interrupt
> line will be filled later on.
> 
> Signed-off-by: Cédric Le Goater <address@hidden>
> ---
> 
>  Changes since v1:
> 
>  - merged in the same patch the qemu_irq handlers
>  - reworked the event notification logic of the qemu_irq handlers.  
>  - introduced XIVE_ESB_STORE_EOI support
>  - removed 'esb_shift' field 
>  - removed a useless check on the validity of the IVE in the memory
>    region handlers.
>  - fixed spapr_xive_pq_trigger() to return true when XIVE_ESB_QUEUED
>    is set
>  - removed the overall ESB memory region. We now have only one region
>    for the provisioned sources.
>  - improved 'info pic' output
> 
>  hw/intc/spapr_xive.c        | 254 
> +++++++++++++++++++++++++++++++++++++++++++-
>  hw/intc/xive-internal.h     |  10 ++
>  include/hw/ppc/spapr_xive.h |   9 ++
>  3 files changed, 271 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/intc/spapr_xive.c b/hw/intc/spapr_xive.c
> index e6e8841add17..43df6814619d 100644
> --- a/hw/intc/spapr_xive.c
> +++ b/hw/intc/spapr_xive.c
> @@ -18,23 +18,252 @@
>  
>  #include "xive-internal.h"
>  
> +static void spapr_xive_irq(sPAPRXive *xive, int lisn)
> +{
> +
> +}
> +
>  /*
> - * Main XIVE object
> + * XIVE Interrupt Source
> + */
> +
> +/*
> + * "magic" Event State Buffer (ESB) MMIO offsets.
> + *
> + * Each interrupt source has a 2-bit state machine called ESB
> + * which can be controlled by MMIO. It's made of 2 bits, P and
> + * Q. P indicates that an interrupt is pending (has been sent
> + * to a queue and is waiting for an EOI). Q indicates that the
> + * interrupt has been triggered while pending.
> + *
> + * This acts as a coalescing mechanism in order to guarantee
> + * that a given interrupt only occurs at most once in a queue.
> + *
> + * When doing an EOI, the Q bit will indicate if the interrupt
> + * needs to be re-triggered.
> + *
> + * The following offsets into the ESB MMIO allow to read or
> + * manipulate the PQ bits. They must be used with an 8-bytes
> + * load instruction. They all return the previous state of the
> + * interrupt (atomically).
> + *
> + * Additionally, some ESB pages support doing an EOI via a
> + * store at 0 and some ESBs support doing a trigger via a
> + * separate trigger page.
> + */
> +#define XIVE_ESB_STORE_EOI      0x400 /* Store */
> +#define XIVE_ESB_LOAD_EOI       0x000 /* Load */
> +#define XIVE_ESB_GET            0x800 /* Load */
> +#define XIVE_ESB_SET_PQ_00      0xc00 /* Load */
> +#define XIVE_ESB_SET_PQ_01      0xd00 /* Load */
> +#define XIVE_ESB_SET_PQ_10      0xe00 /* Load */
> +#define XIVE_ESB_SET_PQ_11      0xf00 /* Load */
> +
> +#define XIVE_ESB_VAL_P          0x2
> +#define XIVE_ESB_VAL_Q          0x1
> +
> +#define XIVE_ESB_RESET          0x0
> +#define XIVE_ESB_PENDING        XIVE_ESB_VAL_P
> +#define XIVE_ESB_QUEUED         (XIVE_ESB_VAL_P | XIVE_ESB_VAL_Q)
> +#define XIVE_ESB_OFF            XIVE_ESB_VAL_Q
> +
> +static uint8_t spapr_xive_pq_get(sPAPRXive *xive, uint32_t lisn)
> +{
> +    uint32_t byte = lisn / 4;
> +    uint32_t bit  = (lisn % 4) * 2;
> +
> +    assert(byte < xive->sbe_size);
> +
> +    return (xive->sbe[byte] >> bit) & 0x3;
> +}
> +
> +static uint8_t spapr_xive_pq_set(sPAPRXive *xive, uint32_t lisn, uint8_t pq)
> +{
> +    uint32_t byte = lisn / 4;
> +    uint32_t bit  = (lisn % 4) * 2;
> +    uint8_t old, new;
> +
> +    assert(byte < xive->sbe_size);
> +
> +    old = xive->sbe[byte];
> +
> +    new = xive->sbe[byte] & ~(0x3 << bit);
> +    new |= (pq & 0x3) << bit;
> +
> +    xive->sbe[byte] = new;
> +
> +    return (old >> bit) & 0x3;
> +}
> +
> +static bool spapr_xive_pq_eoi(sPAPRXive *xive, uint32_t lisn)
> +{
> +    uint8_t old_pq = spapr_xive_pq_get(xive, lisn);
> +
> +    switch (old_pq) {
> +    case XIVE_ESB_RESET:
> +        spapr_xive_pq_set(xive, lisn, XIVE_ESB_RESET);
> +        return false;
> +    case XIVE_ESB_PENDING:
> +        spapr_xive_pq_set(xive, lisn, XIVE_ESB_RESET);
> +        return false;
> +    case XIVE_ESB_QUEUED:
> +        spapr_xive_pq_set(xive, lisn, XIVE_ESB_PENDING);
> +        return true;
> +    case XIVE_ESB_OFF:
> +        spapr_xive_pq_set(xive, lisn, XIVE_ESB_OFF);
> +        return false;
> +    default:
> +         g_assert_not_reached();
> +    }
> +}
> +
> +/*
> + * Returns whether the event notification should be forwarded to the
> + * IVE for routing.
>   */
> +static bool spapr_xive_pq_trigger(sPAPRXive *xive, uint32_t lisn)
> +{
> +    uint8_t old_pq = spapr_xive_pq_get(xive, lisn);
>  
> +    switch (old_pq) {
> +    case XIVE_ESB_RESET:
> +        spapr_xive_pq_set(xive, lisn, XIVE_ESB_PENDING);
> +        return true;
> +    case XIVE_ESB_PENDING:
> +        spapr_xive_pq_set(xive, lisn, XIVE_ESB_QUEUED);
> +        return false;
> +    case XIVE_ESB_QUEUED:
> +        spapr_xive_pq_set(xive, lisn, XIVE_ESB_QUEUED);
> +        return false;
> +    case XIVE_ESB_OFF:
> +        spapr_xive_pq_set(xive, lisn, XIVE_ESB_OFF);
> +        return false;
> +    default:
> +         g_assert_not_reached();
> +    }
> +}
> +
> +/*
> + * XIVE Interrupt Source MMIOs
> + */
> +
> +/*
> + * Some HW use a separate page for trigger. We only support the case
> + * in which the trigger can be done in the same page as the EOI.
> + */
> +static uint64_t spapr_xive_esb_read(void *opaque, hwaddr addr, unsigned size)
> +{
> +    sPAPRXive *xive = SPAPR_XIVE(opaque);
> +    uint32_t offset = addr & 0xF00;
> +    uint32_t lisn = addr >> ESB_SHIFT;
> +    uint64_t ret = -1;
> +
> +    switch (offset) {
> +    case XIVE_ESB_LOAD_EOI:
> +        /*
> +         * EOI on load is not used anymore as we now advertise
> +         * XIVE_ESB_STORE_EOI support for the interrupt sources
> +         */
> +        ret = spapr_xive_pq_eoi(xive, lisn);
> +        break;
> +
> +    case XIVE_ESB_GET:
> +        ret = spapr_xive_pq_get(xive, lisn);
> +        break;
> +
> +    case XIVE_ESB_SET_PQ_00:
> +    case XIVE_ESB_SET_PQ_01:
> +    case XIVE_ESB_SET_PQ_10:
> +    case XIVE_ESB_SET_PQ_11:
> +        ret = spapr_xive_pq_set(xive, lisn, (offset >> 8) & 0x3);
> +        break;
> +    default:
> +        qemu_log_mask(LOG_GUEST_ERROR, "XIVE: invalid ESB addr %d\n", 
> offset);
> +    }
> +
> +    return ret;
> +}
> +
> +static void spapr_xive_esb_write(void *opaque, hwaddr addr,
> +                                 uint64_t value, unsigned size)
> +{
> +    sPAPRXive *xive = SPAPR_XIVE(opaque);
> +    uint32_t offset = addr & 0xF00;
> +    uint32_t lisn = addr >> ESB_SHIFT;
> +    bool notify = false;
> +
> +    switch (offset) {
> +    case 0:
> +        notify = spapr_xive_pq_trigger(xive, lisn);
> +        break;
> +    case XIVE_ESB_STORE_EOI:
> +        /* If the Q bit is set, we should forward a new source event
> +         * notification
> +         */
> +        notify = spapr_xive_pq_eoi(xive, lisn);
> +        break;
> +    default:
> +        qemu_log_mask(LOG_GUEST_ERROR, "XIVE: invalid ESB write addr %d\n",
> +                      offset);
> +        return;
> +    }
> +
> +    /* Forward the source event notification for routing */
> +    if (notify) {
> +        spapr_xive_irq(xive, lisn);
> +    }
> +}
> +
> +static const MemoryRegionOps spapr_xive_esb_ops = {
> +    .read = spapr_xive_esb_read,
> +    .write = spapr_xive_esb_write,
> +    .endianness = DEVICE_BIG_ENDIAN,
> +    .valid = {
> +        .min_access_size = 8,
> +        .max_access_size = 8,
> +    },
> +    .impl = {
> +        .min_access_size = 8,
> +        .max_access_size = 8,
> +    },
> +};
> +
> +static void spapr_xive_source_set_irq(void *opaque, int lisn, int val)
> +{
> +    sPAPRXive *xive = SPAPR_XIVE(opaque);
> +    bool notify = false;
> +
> +    if (val) {
> +        notify = spapr_xive_pq_trigger(xive, lisn);
> +    }
> +
> +    /* Forward the source event notification for routing */
> +    if (notify) {
> +        spapr_xive_irq(xive, lisn);
> +    }
> +}
> +
> +/*
> + * Main XIVE object
> + */
>  void spapr_xive_pic_print_info(sPAPRXive *xive, Monitor *mon)
>  {
>      int i;
>  
>      for (i = 0; i < xive->nr_irqs; i++) {
>          XiveIVE *ive = &xive->ivt[i];
> +        uint8_t pq;
>  
>          if (!(ive->w & IVE_VALID)) {
>              continue;
>          }
>  
> -        monitor_printf(mon, "  %4x %s %08x %08x\n", i,
> +        pq = spapr_xive_pq_get(xive, i);
> +
> +        monitor_printf(mon, "  %4x %s %c%c %08x %08x\n", i,
>                         ive->w & IVE_MASKED ? "M" : " ",
> +                       pq & XIVE_ESB_VAL_P ? 'P' : '-',
> +                       pq & XIVE_ESB_VAL_Q ? 'Q' : '-',
>                         (int) GETFIELD(IVE_EQ_INDEX, ive->w),
>                         (int) GETFIELD(IVE_EQ_DATA, ive->w));
>      }
> @@ -52,6 +281,9 @@ static void spapr_xive_reset(DeviceState *dev)
>              ive->w |= IVE_MASKED;
>          }
>      }
> +
> +    /* SBEs are initialized to 0b01 which corresponds to "ints off" */
> +    memset(xive->sbe, 0x55, xive->sbe_size);
>  }
>  
>  static void spapr_xive_realize(DeviceState *dev, Error **errp)
> @@ -65,6 +297,23 @@ static void spapr_xive_realize(DeviceState *dev, Error 
> **errp)
>  
>      /* Allocate the IVT (Interrupt Virtualization Table) */
>      xive->ivt = g_new0(XiveIVE, xive->nr_irqs);
> +
> +    /* QEMU IRQs */
> +    xive->qirqs = qemu_allocate_irqs(spapr_xive_source_set_irq, xive,
> +                                     xive->nr_irqs);
> +
> +    /* Allocate SBEs (State Bit Entry). 2 bits, so 4 entries per byte */
> +    xive->sbe_size = DIV_ROUND_UP(xive->nr_irqs, 4);
> +    xive->sbe = g_malloc0(xive->sbe_size);
> +
> +    /* VC BAR. Use address of chip 0 to install the ESB memory region
> +     * for *all* interrupt sources */
> +    xive->esb_base = (P9_MMIO_BASE | VC_BAR_DEFAULT);
> +
> +    memory_region_init_io(&xive->esb_iomem, OBJECT(xive),
> +                          &spapr_xive_esb_ops, xive, "xive.esb",
> +                          (1ull << ESB_SHIFT) * xive->nr_irqs);
> +    sysbus_init_mmio(SYS_BUS_DEVICE(dev), &xive->esb_iomem);
>  }
>  
>  static const VMStateDescription vmstate_spapr_xive_ive = {
> @@ -92,6 +341,7 @@ static const VMStateDescription vmstate_spapr_xive = {
>          VMSTATE_UINT32_EQUAL(nr_irqs, sPAPRXive, NULL),
>          VMSTATE_STRUCT_VARRAY_UINT32(ivt, sPAPRXive, nr_irqs, 1,
>                                       vmstate_spapr_xive_ive, XiveIVE),
> +        VMSTATE_VBUFFER_UINT32(sbe, sPAPRXive, 1, NULL, sbe_size),
>          VMSTATE_END_OF_LIST()
>      },
>  };
> diff --git a/hw/intc/xive-internal.h b/hw/intc/xive-internal.h
> index 132b71a6daf0..872648dd96a2 100644
> --- a/hw/intc/xive-internal.h
> +++ b/hw/intc/xive-internal.h
> @@ -16,6 +16,16 @@
>  #define SETFIELD(m, v, val)                             \
>          (((v) & ~(m)) | ((((typeof(v))(val)) << MASK_TO_LSH(m)) & (m)))
>  
> +/*
> + * XIVE MMIO regions
> + */
> +#define P9_MMIO_BASE     0x006000000000000ull
> +
> +/* VC BAR contains set translations for the ESBs and the EQs. */
> +#define VC_BAR_DEFAULT   0x10000000000ull
> +#define VC_BAR_SIZE      0x08000000000ull
> +#define ESB_SHIFT        16 /* One 64k page. OPAL has two */
> +
>  /* IVE/EAS
>   *
>   * One per interrupt source. Targets that interrupt to a given EQ
> diff --git a/include/hw/ppc/spapr_xive.h b/include/hw/ppc/spapr_xive.h
> index 5b1f78e06a1e..ecc15d889b74 100644
> --- a/include/hw/ppc/spapr_xive.h
> +++ b/include/hw/ppc/spapr_xive.h
> @@ -24,8 +24,17 @@ struct sPAPRXive {
>      /* Properties */
>      uint32_t     nr_irqs;
>  
> +    /* IRQ */
> +    qemu_irq     *qirqs;
> +
>      /* XIVE internal tables */
>      XiveIVE      *ivt;
> +    uint8_t      *sbe;
> +    uint32_t     sbe_size;
> +
> +    /* ESB memory region */
> +    hwaddr       esb_base;
> +    MemoryRegion esb_iomem;
>  };
>  
>  bool spapr_xive_irq_enable(sPAPRXive *xive, uint32_t lisn);

-- 
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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