Re: [Qemu-devel] [PATCH 2/3] arm_gicv2m: Add GICv2m widget to support MSIs

[Eric Auger <eric.auger@linaro.org>]

On 04/10/2015 11:58 AM, Christoffer Dall wrote:
> On Fri, Apr 10, 2015 at 11:16:57AM +0200, Eric Auger wrote:
>> Hi Christoffer,
>> On 04/08/2015 11:20 PM, Christoffer Dall wrote:
>>> The ARM GICv2m widget is a little device that handle MSI interrupt
>>> writes to a trigger register and ties them to a range of interrupt lines
>>> wires to the GIC.  It has a few status/id registers and the interrupt wires,
>>> and that's about it.
>>>
>>> A board instantiates the device by setting the base SPI number and
>>> number SPIs for the frame.  The base-spi parameter is indexed in the SPI
>>> number space only, so base-spi == 0, means IRQ number 32.  When a device
>>> (the PCI host controller) writes to the trigger register, the payload is
>>> the GIC IRQ number, so we have to subtract 32 from that and then index
>>> into our frame of SPIs.
>>>
>>> When instantiating a GICv2m device, tell PCI that we have instantiated
>>> something that can deal with MSIs.  We rely on the board actually wiring
>>> up the GICv2m to the PCI host controller.
>>>
>>> Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
>>> ---
>>>  hw/intc/Makefile.objs |   1 +
>>>  hw/intc/arm_gicv2m.c  | 180 ++++++++++++++++++++++++++++++++++++++++++++++++++
>>>  2 files changed, 181 insertions(+)
>>>  create mode 100644 hw/intc/arm_gicv2m.c
>>>
>>> diff --git a/hw/intc/Makefile.objs b/hw/intc/Makefile.objs
>>> index 843864a..6b63dfc 100644
>>> --- a/hw/intc/Makefile.objs
>>> +++ b/hw/intc/Makefile.objs
>>> @@ -15,6 +15,7 @@ common-obj-$(CONFIG_OPENPIC) += openpic.o
>>>  
>>>  obj-$(CONFIG_APIC) += apic.o apic_common.o
>>>  obj-$(CONFIG_ARM_GIC_KVM) += arm_gic_kvm.o
>>> +obj-$(CONFIG_ARM_GIC) += arm_gicv2m.o
>> we could put this above close to the other common-obj-$(CONFIG_ARM_GIC)
>> objects?
> 
> I'm honestly not quite sure what the difference between common-obj-y and
> obj-y is?
> 
>>>  obj-$(CONFIG_STELLARIS) += armv7m_nvic.o
>>>  obj-$(CONFIG_EXYNOS4) += exynos4210_gic.o exynos4210_combiner.o
>>>  obj-$(CONFIG_GRLIB) += grlib_irqmp.o
>>> diff --git a/hw/intc/arm_gicv2m.c b/hw/intc/arm_gicv2m.c
>>> new file mode 100644
>>> index 0000000..a80a16d
>>> --- /dev/null
>>> +++ b/hw/intc/arm_gicv2m.c
>>> @@ -0,0 +1,180 @@
>>> +/*
>>> + *  GICv2m extension for MSI/MSI-x support with a GICv2-based system
>>> + *
>>> + * Copyright (C) 2015 Linaro, All rights reserved.
>>> + *
>>> + * Author: Christoffer Dall <christoffer.dall@linaro.org>
>>> + *
>>> + * This library is free software; you can redistribute it and/or
>>> + * modify it under the terms of the GNU Lesser General Public
>>> + * License as published by the Free Software Foundation; either
>>> + * version 2 of the License, or (at your option) any later version.
>>> + *
>>> + * This library is distributed in the hope that it will be useful,
>>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>>> + * Lesser General Public License for more details.
>>> + *
>>> + * You should have received a copy of the GNU Lesser General Public
>>> + * License along with this library; if not, see <http://www.gnu.org/licenses/>.
>>> + */
>>> +
>>> +#include "hw/sysbus.h"
>>> +#include "hw/pci/msi.h"
>>> +
>>> +#define TYPE_GICV2M "gicv2m"
>>> +#define GICV2M(obj) OBJECT_CHECK(GICv2mState, (obj), TYPE_GICV2M)
>>> +
>>> +#define GICV2M_NUM_SPI_MAX 128
>>> +
>> Maybe we could add a comment that the model supports a single non secure
>> MSI register frame
> 
> Isn't that already part of the GICv2m specification and hence implied
> for emulating a gicv2m?
> 
>>> +#define V2M_MSI_TYPER           0x008
>>> +#define V2M_MSI_SETSPI_NS       0x040
>>> +#define V2M_MSI_IIDR            0xFCC
>>> +#define V2M_IIDR0               0xFD0
>>> +
>>> +#define PRODUCT_ID_QEMU         0x51 /* ASCII code Q */
>>> +#define IMPLEMENTER_ARM         0x43b
>>> +
>>> +typedef struct GICv2mState {
>>> +    SysBusDevice parent_obj;
>>> +
>>> +    MemoryRegion iomem;
>>> +    qemu_irq spi[GICV2M_NUM_SPI_MAX];
>>> +
>> /* first absolute SPI index */, to avoid mixing with ID?
> 
> not sure this comment helps, I think reading the code is actually more
> clear, unless you can think of an even more clear wording for the
> comment?
> 
>>> +    uint32_t base_spi;
>>> +    uint32_t num_spi;
>>> +} GICv2mState;
>>> +
>>> +static void gicv2m_set_irq(void *opaque, int irq)
>>> +{
>>> +    GICv2mState *s = (GICv2mState *)opaque;
>>> +
>>> +    qemu_irq_pulse(s->spi[irq]);
>>> +}
>>> +
>>> +static uint64_t gicv2m_read(void *opaque, hwaddr offset,
>>> +                            unsigned size)
>>> +{
>>> +    GICv2mState *s = (GICv2mState *)opaque;
>>> +    uint32_t val;
>>> +
>>> +    if (size != 4) {
>>> +        qemu_log_mask(LOG_GUEST_ERROR, "gicv2m_read: bad size %u\n", size);
>>> +        return 0;
>>> +    }
>>> +
>>> +    switch (offset) {
>>> +    case V2M_MSI_TYPER:
>>> +        val = (s->base_spi + 32) << 16;
>>> +        val |= s->num_spi;
>>> +        return val;
>>> +    case V2M_MSI_IIDR:
>>> +        return (PRODUCT_ID_QEMU << 20) | IMPLEMENTER_ARM;
>> I guess there is a single arch revision (0?), [19:16]
> 
> yes, see the spec.
> 
>>> +    default:
>>> +        if (offset > V2M_IIDR0 && offset <= 0xFFC) {
>> /* Peripheral ID2 reg */?
>>> +            return 0;
>>> +        }
>>> +
>> /* reserved */?
>>> +        qemu_log_mask(LOG_GUEST_ERROR,
>>> +                      "gicv2m_read: Bad offset %x\n", (int)offset);
>>> +        return 0;
>>> +    }
>>> +}
>>> +
>>> +static void gicv2m_write(void *opaque, hwaddr offset,
>>> +                        uint64_t value, unsigned size)
>>> +{
>>> +    GICv2mState *s = (GICv2mState *)opaque;
>>> +
>>> +    if (size != 4) {
>>> +        qemu_log_mask(LOG_GUEST_ERROR, "gicv2m_write: bad size %u\n", size);
>>> +        return;
>>> +    }
>>> +
>>> +    switch (offset) {
>>> +    case V2M_MSI_SETSPI_NS: {
>>> +        int spi;
>>> +
>>> +        spi = (value & 0x3ff) - (s->base_spi + 32);
>>> +        if (spi < s->num_spi) {
>>> +            gicv2m_set_irq(s, spi);
>>> +        }
>> shouldn't we print an error msg in case spi is not within the frame range?
>> also shouldn't we check spi >= 0?
> 
> no, we should just emulate the behavior of the device, which clearly
> states: "If the resulting value does not identify an SPI that is
> allocated to this frame then the write has no effect." - so no effect is
> what I'm going for :)
OK,

and about spi>= 0?

Eric
> 
> 
> Thanks for the review!
> 
> -Christoffer
>