Re: [Qemu-arm] [PATCH v3 09/10] hw/acpi: Add ACPI Generic Event Device Support

[Shameerali Kolothum Thodi]

Hi Eric,

> -----Original Message-----
> From: Auger Eric [mailto:address@hidden
> Sent: 29 March 2019 13:09
> To: Shameerali Kolothum Thodi <address@hidden>;
> address@hidden; address@hidden; address@hidden;
> address@hidden; address@hidden;
> address@hidden; address@hidden
> Cc: Linuxarm <address@hidden>; xuwei (O) <address@hidden>
> Subject: Re: [PATCH v3 09/10] hw/acpi: Add ACPI Generic Event Device Support
> 
> Hi Shameer,
> 
> On 3/21/19 11:47 AM, Shameer Kolothum wrote:
> > From: Samuel Ortiz <address@hidden>
> >
> > The ACPI Generic Event Device (GED) is a hardware-reduced specific
> > device that handles all platform events, including the hotplug ones.
> > This patch generates the AML code that defines GEDs.
> >
> > Platforms need to specify their own GedEvent array to describe what
> > kind of events they want to support through GED.  Also this uses a
> > a single interrupt for the  GED device, relying on IO memory region
> > to communicate the type of device affected by the interrupt. This
> > way, we can support up to 32 events with a unique interrupt.
> >
> > This is in preparation for making use of GED for ARM/virt
> > platform and for now supports only memory hotplug.
> 
> Personally I would squash this with PATCH 3.

Ok.

> > Signed-off-by: Samuel Ortiz <address@hidden>
> > Signed-off-by: Sebastien Boeuf <address@hidden>
> > Signed-off-by: Shameer Kolothum <address@hidden>
> > ---
> >  hw/acpi/generic_event_device.c         | 200
> +++++++++++++++++++++++++++++++++
> >  include/hw/acpi/generic_event_device.h |  34 ++++++
> >  2 files changed, 234 insertions(+)
> >
> > diff --git a/hw/acpi/generic_event_device.c
> b/hw/acpi/generic_event_device.c
> > index 0b32fc9..9deaa33 100644
> > --- a/hw/acpi/generic_event_device.c
> > +++ b/hw/acpi/generic_event_device.c
> > @@ -23,6 +23,183 @@
> >  #include "hw/acpi/generic_event_device.h"
> >  #include "hw/mem/pc-dimm.h"
> >
> > +static hwaddr ged_io_base;
> > +static GedEvent *ged_events;
> > +static uint32_t ged_events_size;
> > +
> > +static Aml *ged_event_aml(const GedEvent *event)
> > +{
> > +
> > +    if (!event) {
> > +        return NULL;
> > +    }
> > +
> > +    switch (event->event) {
> > +    case GED_MEMORY_HOTPLUG:
> > +        /* We run a complete memory SCAN when getting a memory
> hotplug event */
> > +        return aml_call0(MEMORY_DEVICES_CONTAINER "."
> MEMORY_SLOT_SCAN_METHOD);
> > +    default:
> > +        break;
> > +    }
> > +
> > +    return NULL;
> > +}
> > +
> > +/*
> > + * The ACPI Generic Event Device (GED) is a hardware-reduced specific
> > + * device[ACPI v6.1 Section 5.6.9] that handles all platform events,
> > + * including the hotplug ones. Platforms need to specify their own
> > + * GedEvent array to describe what kind of events they want to support
> > + * through GED. This routine uses a single interrupt for the GED device,
> > + * relying on IO memory region to communicate the type of device
> > + * affected by the interrupt. This way, we can support up to 32 events
> > + * with a unique interrupt.
> 
> During last review I asked the question herefater. I may have missed
> your answer but just in case.
> 
> 5.6.9.1 says:
> "
> The platform declare its support for the GED, and query whether an OS
> supports it, via the _OSC method
> "
> Is it something done?

Yes you did raise this earlier and I had replied as well :).

https://patchwork.kernel.org/patch/10844557/

" Right. _OSC is not defined and I don’t see Qemu ever defined platform wide 
OSPM capabilities. I can see that it does that for PCI/PCIe hierarchies. 

Moreover looking at the Linux code, it doesn’t seems to care about
GED definition either,
https://elixir.bootlin.com/linux/v5.0/source/include/linux/acpi.h#L490

I can try adding _OSC declaring just the GED bit for future, but not sure
It makes much difference as of now. 

Please let me know if there is a strong argument for it.
"

> > + */
> > +void build_ged_aml(Aml *table, const char *name, uint32_t ged_irq,
> > +                   AmlRegionSpace rs)
> > +{
> > +    Aml *crs = aml_resource_template();
> > +    Aml *evt, *field;
> > +    Aml *dev = aml_device("%s", name);
> > +    Aml *irq_sel = aml_local(0);
> > +    Aml *isel = aml_name(AML_GED_IRQ_SEL);
> > +    uint32_t i;
> > +
> > +    if (!ged_io_base || !ged_events || !ged_events_size) {
> > +        return;
> > +    }
> > +
> > +    /* _CRS interrupt */
> > +    aml_append(crs, aml_interrupt(AML_CONSUMER, AML_EDGE,
> AML_ACTIVE_HIGH,
> > +                                  AML_EXCLUSIVE, &ged_irq, 1));
> > +    /*
> > +     * For each GED event we:
> > +     * - Add an interrupt to the CRS section.
> > +     * - Add a conditional block for each event, inside a while loop.
> > +     *   This is semantically equivalent to a switch/case implementation.
> > +     */
> > +    evt = aml_method("_EVT", 1, AML_SERIALIZED);
> > +    {
> > +        Aml *ged_aml;
> > +        Aml *if_ctx;
> > +
> > +        /* Local0 = ISEL */
> > +        aml_append(evt, aml_store(isel, irq_sel));
> > +
> > +        /*
> > +         * Here we want to call a method for each supported GED event
> type.
> > +         * The resulting ASL code looks like:
> > +         *
> > +         * Local0 = ISEL
> > +         * If ((Local0 & irq0) == irq0)
> > +         * {
> > +         *     MethodEvent0()
> > +         * }
> > +         *
> > +         * If ((Local0 & irq1) == irq1)
> > +         * {
> > +         *     MethodEvent1()
> > +         * }
> I think we could have stopped here ;-) with a ../..

Ok

> > +         *
> > +         * If ((Local0 & irq2) == irq2)
> > +         * {
> > +         *     MethodEvent2()
> > +         * }
> > +         */
> > +
> > +        for (i = 0; i < ged_events_size; i++) {
> > +            ged_aml = ged_event_aml(&ged_events[i]);
> > +            if (!ged_aml) {
> > +                continue;
> > +            }
> > +
> > +            /* If ((Local1 == irq))*/
> > +            if_ctx = aml_if(aml_equal(aml_and(irq_sel,
> aml_int(ged_events[i].selector), NULL), aml_int(ged_events[i].selector)));
> doesn't check_patch complain here?

It did warn but thought this has better readability. I will address this.

> > +            {
> > +                /* AML for this specific type of event */
> > +                aml_append(if_ctx, ged_aml);
> > +            }
> > +
> > +            /*
> > +             * We append the first "if" to the "while" context.
> > +             * Other "ifs" will be "elseifs".
> > +             */
> > +            aml_append(evt, if_ctx);
> > +        }
> > +    }
> > +
> > +    aml_append(dev, aml_name_decl("_HID", aml_string("ACPI0013")));
> > +    aml_append(dev, aml_name_decl("_UID", aml_string(GED_DEVICE)));
> > +    aml_append(dev, aml_name_decl("_CRS", crs));
> > +
> > +    /* Append IO region */
> > +    aml_append(dev, aml_operation_region(AML_GED_IRQ_REG, rs,
> > +               aml_int(ged_io_base + ACPI_GED_IRQ_SEL_OFFSET),
> > +               ACPI_GED_IRQ_SEL_LEN));
> > +    field = aml_field(AML_GED_IRQ_REG, AML_DWORD_ACC,
> AML_NOLOCK,
> > +                      AML_WRITE_AS_ZEROS);
> > +    aml_append(field, aml_named_field(AML_GED_IRQ_SEL,
> > +                                      ACPI_GED_IRQ_SEL_LEN *
> 8));
> > +    aml_append(dev, field);
> > +
> > +    /* Append _EVT method */
> > +    aml_append(dev, evt);
> > +
> > +    aml_append(table, dev);
> > +}
> > +
> > +/* Memory read by the GED _EVT AML dynamic method */
> > +static uint64_t ged_read(void *opaque, hwaddr addr, unsigned size)
> > +{
> > +    uint64_t val = 0;
> > +    GEDState *ged_st = opaque;
> > +
> > +    switch (addr) {
> > +    case ACPI_GED_IRQ_SEL_OFFSET:
> > +        /* Read the selector value and reset it */
> > +        qemu_mutex_lock(&ged_st->lock);
> > +        val = ged_st->sel;
> > +        ged_st->sel = 0;
> > +        qemu_mutex_unlock(&ged_st->lock);
> > +        break;
> > +    default:
> > +        break;
> > +    }
> > +
> > +    return val;
> > +}
> > +
> > +/* Nothing is expected to be written to the GED memory region */
> > +static void ged_write(void *opaque, hwaddr addr, uint64_t data,
> > +                      unsigned int size)
> > +{
> > +}
> > +
> > +static const MemoryRegionOps ged_ops = {
> > +    .read = ged_read,
> > +    .write = ged_write,
> > +    .endianness = DEVICE_LITTLE_ENDIAN,
> > +    .valid = {
> > +        .min_access_size = 4,
> > +        .max_access_size = 4,
> > +    },
> > +};
> > +
> > +static void acpi_ged_event(GEDState *ged_st, uint32_t ged_irq_sel)
> > +{
> > +    /*
> > +     * Set the GED IRQ selector to the expected device type value. This
> > +     * way, the ACPI method will be able to trigger the right code based
> > +     * on a unique IRQ.
> > +     */
> > +    qemu_mutex_lock(&ged_st->lock);
> > +    ged_st->sel = ged_irq_sel;
> > +    qemu_mutex_unlock(&ged_st->lock);
> > +
> > +    /* Trigger the event by sending an interrupt to the guest. */
> > +    qemu_irq_pulse(ged_st->gsi[ged_st->irq]);
> I don't get this. The devices uses a single irq, right?

Yes it uses single irq.

> Why can't we do like other sysbus devices, sysbus_init_irq(dev, &s->irq);
> and use
> sysbus_connect_irq(SYS_BUS_DEVICE(dev), i, pic); in virt?

I have to take a look at this.

> > +}
> > +
> >  static void virt_device_plug_cb(HotplugHandler *hotplug_dev,
> >                                  DeviceState *dev, Error **errp)
> >  {
> > @@ -40,6 +217,21 @@ static void virt_device_plug_cb(HotplugHandler
> *hotplug_dev,
> >
> >  static void virt_send_ged(AcpiDeviceIf *adev, AcpiEventStatusBits ev)
> >  {
> > +    VirtAcpiState *s = VIRT_ACPI(adev);
> > +    uint32_t sel;
> > +
> > +    if (ev & ACPI_MEMORY_HOTPLUG_STATUS) {
> > +        sel = ACPI_GED_IRQ_SEL_MEM;
> > +    } else {
> > +        /* Unknown event. Return without generating interrupt. */
> > +        return;
> > +    }
> > +
> > +    /*
> > +     * We inject the hotplug interrupt. The IRQ selector will make
> > +     * the difference from the ACPI table.
> > +     */
> > +    acpi_ged_event(&s->ged_state, sel);
> >  }
> >
> >  static void virt_device_realize(DeviceState *dev, Error **errp)
> > @@ -57,6 +249,11 @@ static Property virt_acpi_properties[] = {
> >      DEFINE_PROP_UINT64("memhp_base", VirtAcpiState, memhp_base,
> 0),
> >      DEFINE_PROP_BOOL("memory-hotplug-support", VirtAcpiState,
> >                       memhp_state.is_enabled, true),
> It may be worth to explain why the GED device owns the
> MEMORY_HOTPLUG_MMIO region. This was and still is confusing me I
> acknowledge.

I will try to add the comment here saying this is the hotplug handler/
acpi interface device and needs to initialize the memory hotplug base
region.

> > +    DEFINE_PROP_PTR("gsi", VirtAcpiState, gsi),
> see the comment abour irq above.
> > +    DEFINE_PROP_UINT64("ged_base", VirtAcpiState, ged_base, 0),
> > +    DEFINE_PROP_UINT32("ged_irq", VirtAcpiState, ged_irq, 0),
> > +    DEFINE_PROP_PTR("ged_events", VirtAcpiState, ged_events),
> > +    DEFINE_PROP_UINT32("ged_events_size", VirtAcpiState,
> ged_events_size, 0),
> >      DEFINE_PROP_END_OF_LIST(),
> >  };
> >
> > @@ -70,6 +267,9 @@ static void virt_acpi_class_init(ObjectClass *class,
> void *data)
> >      dc->props = virt_acpi_properties;
> >      dc->realize = virt_device_realize;
> >
> > +    /* Reason: pointer properties "gsi" and "gde_events" */
> ged_events

Thanks,
Shameer

> > +    dc->user_creatable = false;
> > +
> >      hc->plug = virt_device_plug_cb;
> >
> >      adevc->send_event = virt_send_ged;
> > diff --git a/include/hw/acpi/generic_event_device.h
> b/include/hw/acpi/generic_event_device.h
> > index 262ca7d..7f130f3 100644
> > --- a/include/hw/acpi/generic_event_device.h
> > +++ b/include/hw/acpi/generic_event_device.h
> > @@ -24,11 +24,45 @@
> >  #define VIRT_ACPI(obj) \
> >      OBJECT_CHECK(VirtAcpiState, (obj), TYPE_VIRT_ACPI)
> >
> > +#define ACPI_GED_IRQ_SEL_OFFSET 0x0
> > +#define ACPI_GED_IRQ_SEL_LEN    0x4
> > +#define ACPI_GED_IRQ_SEL_MEM    0x1
> > +#define ACPI_GED_REG_LEN        0x4
> > +
> > +#define GED_DEVICE      "GED"
> > +#define AML_GED_IRQ_REG "IREG"
> > +#define AML_GED_IRQ_SEL "ISEL"
> > +
> > +typedef enum {
> > +    GED_MEMORY_HOTPLUG = 1,
> > +} GedEventType;
> > +
> > +typedef struct GedEvent {
> > +    uint32_t     selector;
> > +    GedEventType event;
> > +} GedEvent;
> > +
> > +typedef struct GEDState {
> > +    MemoryRegion io;
> > +    uint32_t     sel;
> > +    uint32_t     irq;
> > +    qemu_irq     *gsi;
> > +    QemuMutex    lock;
> > +} GEDState;
> > +
> >  typedef struct VirtAcpiState {
> >      SysBusDevice parent_obj;
> >      MemHotplugState memhp_state;
> >      hwaddr memhp_base;
> > +    void *gsi;
> > +    hwaddr ged_base;
> > +    GEDState ged_state;
> > +    uint32_t ged_irq;
> > +    void *ged_events;
> > +    uint32_t ged_events_size;
> >  } VirtAcpiState;
> >
> > +void build_ged_aml(Aml *table, const char* name, uint32_t ged_irq,
> > +                   AmlRegionSpace rs);
> >
> >  #endif
> >
> 
> Thanks
> 
> Eric