Re: [Qemu-devel] [PATCH v5 06/36] ppc/xive: add support for the END Event State buffers

["Cédric Le Goater" <clg@kaod.org>]

On 11/22/18 6:13 AM, David Gibson wrote:
> On Fri, Nov 16, 2018 at 11:56:59AM +0100, Cédric Le Goater wrote:
>> The Event Notification Descriptor also contains two Event State
>> Buffers providing further coalescing of interrupts, one for the
>> notification event (ESn) and one for the escalation events (ESe). A
>> MMIO page is assigned for each to control the EOI through loads
>> only. Stores are not allowed.
>>
>> The END ESBs are modeled through an object resembling the 'XiveSource'
>> It is stateless as the END state bits are backed into the XiveEND
>> structure under the XiveRouter and the MMIO accesses follow the same
>> rules as for the standard source ESBs.
>>
>> END ESBs are not supported by the Linux drivers neither on OPAL nor on
>> sPAPR. Nevetherless, it provides a mean to study the question in the
>> future and validates a bit more the XIVE model.
>>
>> Signed-off-by: Cédric Le Goater <clg@kaod.org>
>> ---
>>  include/hw/ppc/xive.h |  20 ++++++
>>  hw/intc/xive.c        | 160 +++++++++++++++++++++++++++++++++++++++++-
>>  2 files changed, 178 insertions(+), 2 deletions(-)
>>
>> diff --git a/include/hw/ppc/xive.h b/include/hw/ppc/xive.h
>> index ce62aaf28343..24301bf2076d 100644
>> --- a/include/hw/ppc/xive.h
>> +++ b/include/hw/ppc/xive.h
>> @@ -208,6 +208,26 @@ int xive_router_get_end(XiveRouter *xrtr, uint8_t end_blk, uint32_t end_idx,
>>  int xive_router_set_end(XiveRouter *xrtr, uint8_t end_blk, uint32_t end_idx,
>>                          XiveEND *end);
>>  
>> +/*
>> + * XIVE END ESBs
>> + */
>> +
>> +#define TYPE_XIVE_END_SOURCE "xive-end-source"
>> +#define XIVE_END_SOURCE(obj) \
>> +    OBJECT_CHECK(XiveENDSource, (obj), TYPE_XIVE_END_SOURCE)
> 
> Is there a particular reason to make this a full QOM object, rather
> than just embedding it in the XiveRouter?

yes, it should probably be under the XiveRouter you are right because
there is a direct link with the ENDT which is in the XiverRouter. 

But if I remove the chip_id field from the XiveRouter, it becomes a QOM
interface. something to ponder.
 
>> +typedef struct XiveENDSource {
>> +    SysBusDevice parent;
>> +
>> +    uint32_t        nr_ends;
>> +
>> +    /* ESB memory region */
>> +    uint32_t        esb_shift;
>> +    MemoryRegion    esb_mmio;
>> +
>> +    XiveRouter      *xrtr;
>> +} XiveENDSource;
>> +
>>  /*
>>   * For legacy compatibility, the exceptions define up to 256 different
>>   * priorities. P9 implements only 9 levels : 8 active levels [0 - 7]
>> diff --git a/hw/intc/xive.c b/hw/intc/xive.c
>> index 9cb001e7b540..5a8882d47a98 100644
>> --- a/hw/intc/xive.c
>> +++ b/hw/intc/xive.c
>> @@ -622,8 +622,18 @@ static void xive_router_end_notify(XiveRouter *xrtr, uint8_t end_blk,
>>       * even futher coalescing in the Router
>>       */
>>      if (!(end.w0 & END_W0_UCOND_NOTIFY)) {
>> -        qemu_log_mask(LOG_UNIMP, "XIVE: !UCOND_NOTIFY not implemented\n");
>> -        return;
>> +        uint8_t pq = GETFIELD(END_W1_ESn, end.w1);
>> +        bool notify = xive_esb_trigger(&pq);
>> +
>> +        if (pq != GETFIELD(END_W1_ESn, end.w1)) {
>> +            end.w1 = SETFIELD(END_W1_ESn, end.w1, pq);
>> +            xive_router_set_end(xrtr, end_blk, end_idx, &end);
>> +        }
>> +
>> +        /* ESn[Q]=1 : end of notification */
>> +        if (!notify) {
>> +            return;
>> +        }
>>      }
>>  
>>      /*
>> @@ -706,6 +716,151 @@ void xive_eas_pic_print_info(XiveEAS *eas, uint32_t lisn, Monitor *mon)
>>                     (uint32_t) GETFIELD(EAS_END_DATA, eas->w));
>>  }
>>  
>> +/*
>> + * END ESB MMIO loads
>> + */
>> +static uint64_t xive_end_source_read(void *opaque, hwaddr addr, unsigned size)
>> +{
>> +    XiveENDSource *xsrc = XIVE_END_SOURCE(opaque);
>> +    XiveRouter *xrtr = xsrc->xrtr;
>> +    uint32_t offset = addr & 0xFFF;
>> +    uint8_t end_blk;
>> +    uint32_t end_idx;
>> +    XiveEND end;
>> +    uint32_t end_esmask;
>> +    uint8_t pq;
>> +    uint64_t ret = -1;
>> +
>> +    end_blk = xrtr->chip_id;
>> +    end_idx = addr >> (xsrc->esb_shift + 1);
>> +    if (xive_router_get_end(xrtr, end_blk, end_idx, &end)) {
>> +        qemu_log_mask(LOG_GUEST_ERROR, "XIVE: No END %x/%x\n", end_blk,
>> +                      end_idx);
>> +        return -1;
>> +    }
>> +
>> +    if (!(end.w0 & END_W0_VALID)) {
>> +        qemu_log_mask(LOG_GUEST_ERROR, "XIVE: END %x/%x is invalid\n",
>> +                      end_blk, end_idx);
>> +        return -1;
>> +    }
>> +
>> +    end_esmask = addr_is_even(addr, xsrc->esb_shift) ? END_W1_ESn : END_W1_ESe;
>> +    pq = GETFIELD(end_esmask, end.w1);
>> +
>> +    switch (offset) {
>> +    case XIVE_ESB_LOAD_EOI ... XIVE_ESB_LOAD_EOI + 0x7FF:
>> +        ret = xive_esb_eoi(&pq);
>> +
>> +        /* Forward the source event notification for routing ?? */
>> +        break;
>> +
>> +    case XIVE_ESB_GET ... XIVE_ESB_GET + 0x3FF:
>> +        ret = pq;
>> +        break;
>> +
>> +    case XIVE_ESB_SET_PQ_00 ... XIVE_ESB_SET_PQ_00 + 0x0FF:
>> +    case XIVE_ESB_SET_PQ_01 ... XIVE_ESB_SET_PQ_01 + 0x0FF:
>> +    case XIVE_ESB_SET_PQ_10 ... XIVE_ESB_SET_PQ_10 + 0x0FF:
>> +    case XIVE_ESB_SET_PQ_11 ... XIVE_ESB_SET_PQ_11 + 0x0FF:
>> +        ret = xive_esb_set(&pq, (offset >> 8) & 0x3);
>> +        break;
>> +    default:
>> +        qemu_log_mask(LOG_GUEST_ERROR, "XIVE: invalid END ESB load addr %d\n",
>> +                      offset);
>> +        return -1;
>> +    }
>> +
>> +    if (pq != GETFIELD(end_esmask, end.w1)) {
>> +        end.w1 = SETFIELD(end_esmask, end.w1, pq);
>> +        xive_router_set_end(xrtr, end_blk, end_idx, &end);
>> +    }
> 
> We can probably share some more code with XiveSource here, but that's
> something that can be refined later.

yes clearly. The idea was to introduce a XiveESB model handling only the 
MMIO aspects and rely on an interface to query/modify the underlying PQ bits.
These state bits are related to a device and the ESB pages are the XIVE way 
to expose them. 

I left that for later. I didn't want to complexify more the XiveSource 
with a feature not used today. 

Thanks,

C.

> 
>> +
>> +    return ret;
>> +}
>> +
>> +/*
>> + * END ESB MMIO stores are invalid
>> + */
>> +static void xive_end_source_write(void *opaque, hwaddr addr,
>> +                                  uint64_t value, unsigned size)
>> +{
>> +    qemu_log_mask(LOG_GUEST_ERROR, "XIVE: invalid ESB write addr 0x%"
>> +                  HWADDR_PRIx"\n", addr);
>> +}
>> +
>> +static const MemoryRegionOps xive_end_source_ops = {
>> +    .read = xive_end_source_read,
>> +    .write = xive_end_source_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 xive_end_source_realize(DeviceState *dev, Error **errp)
>> +{
>> +    XiveENDSource *xsrc = XIVE_END_SOURCE(dev);
>> +    Object *obj;
>> +    Error *local_err = NULL;
>> +
>> +    obj = object_property_get_link(OBJECT(dev), "xive", &local_err);
>> +    if (!obj) {
>> +        error_propagate(errp, local_err);
>> +        error_prepend(errp, "required link 'xive' not found: ");
>> +        return;
>> +    }
>> +
>> +    xsrc->xrtr = XIVE_ROUTER(obj);
>> +
>> +    if (!xsrc->nr_ends) {
>> +        error_setg(errp, "Number of interrupt needs to be greater than 0");
>> +        return;
>> +    }
>> +
>> +    if (xsrc->esb_shift != XIVE_ESB_4K &&
>> +        xsrc->esb_shift != XIVE_ESB_64K) {
>> +        error_setg(errp, "Invalid ESB shift setting");
>> +        return;
>> +    }
>> +
>> +    /*
>> +     * Each END is assigned an even/odd pair of MMIO pages, the even page
>> +     * manages the ESn field while the odd page manages the ESe field.
>> +     */
>> +    memory_region_init_io(&xsrc->esb_mmio, OBJECT(xsrc),
>> +                          &xive_end_source_ops, xsrc, "xive.end",
>> +                          (1ull << (xsrc->esb_shift + 1)) * xsrc->nr_ends);
>> +    sysbus_init_mmio(SYS_BUS_DEVICE(dev), &xsrc->esb_mmio);
>> +}
>> +
>> +static Property xive_end_source_properties[] = {
>> +    DEFINE_PROP_UINT32("nr-ends", XiveENDSource, nr_ends, 0),
>> +    DEFINE_PROP_UINT32("shift", XiveENDSource, esb_shift, XIVE_ESB_64K),
>> +    DEFINE_PROP_END_OF_LIST(),
>> +};
>> +
>> +static void xive_end_source_class_init(ObjectClass *klass, void *data)
>> +{
>> +    DeviceClass *dc = DEVICE_CLASS(klass);
>> +
>> +    dc->desc    = "XIVE END Source";
>> +    dc->props   = xive_end_source_properties;
>> +    dc->realize = xive_end_source_realize;
>> +}
>> +
>> +static const TypeInfo xive_end_source_info = {
>> +    .name          = TYPE_XIVE_END_SOURCE,
>> +    .parent        = TYPE_SYS_BUS_DEVICE,
>> +    .instance_size = sizeof(XiveENDSource),
>> +    .class_init    = xive_end_source_class_init,
>> +};
>> +
>>  /*
>>   * XIVE Fabric
>>   */
>> @@ -720,6 +875,7 @@ static void xive_register_types(void)
>>      type_register_static(&xive_source_info);
>>      type_register_static(&xive_fabric_info);
>>      type_register_static(&xive_router_info);
>> +    type_register_static(&xive_end_source_info);
>>  }
>>  
>>  type_init(xive_register_types)
>