Re: [PATCH] hw/core: Introduce proxy-pic

[Bernhard Beschow]

Am 5. Januar 2023 09:50:03 UTC schrieb Bernhard Beschow <shentey@gmail.com>:
>
>
>Am 4. Januar 2023 22:22:01 UTC schrieb Mark Cave-Ayland 
><mark.cave-ayland@ilande.co.uk>:
>>On 04/01/2023 19:53, Bernhard Beschow wrote:
>>
>>> Having a proxy PIC allows for ISA PICs to be created and wired up in
>>> southbridges. This is especially useful for PIIX3 for two reasons:
>>> First, the southbridge doesn't need to care about the virtualization
>>> technology used (KVM, TCG, Xen) due to in-IRQs (where devices get
>>> attached) and out-IRQs (which will trigger the IRQs of the respective
>>> virtualization technology) are separated. Second, since the in-IRQs are
>>> populated with fully initialized qemu_irq's, they can already be wired
>>> up inside PIIX3.
>>> 
>>> Signed-off-by: Bernhard Beschow <shentey@gmail.com>
>>> Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
>>> Message-Id: <20221022150508.26830-15-shentey@gmail.com>
>>> ---
>>> Changes since v4:
>>> * Change license to GPL-2.0-or-later and use SPDX-License-Identifier
>>> * Fix typo in commit message
>>> ---
>>>   include/hw/core/proxy-pic.h | 38 ++++++++++++++++++++++++++
>>>   hw/core/proxy-pic.c         | 54 +++++++++++++++++++++++++++++++++++++
>>>   MAINTAINERS                 |  2 ++
>>>   hw/core/Kconfig             |  3 +++
>>>   hw/core/meson.build         |  1 +
>>>   5 files changed, 98 insertions(+)
>>>   create mode 100644 include/hw/core/proxy-pic.h
>>>   create mode 100644 hw/core/proxy-pic.c
>>> 
>>> diff --git a/include/hw/core/proxy-pic.h b/include/hw/core/proxy-pic.h
>>> new file mode 100644
>>> index 0000000000..32bc7936bd
>>> --- /dev/null
>>> +++ b/include/hw/core/proxy-pic.h
>>> @@ -0,0 +1,38 @@
>>> +/*
>>> + * SPDX-License-Identifier: GPL-2.0-or-later
>>> + *
>>> + * Proxy interrupt controller device.
>>> + *
>>> + * Copyright (c) 2022 Bernhard Beschow <shentey@gmail.com>
>>> + */
>>> +
>>> +#ifndef HW_PROXY_PIC_H
>>> +#define HW_PROXY_PIC_H
>>> +
>>> +#include "hw/qdev-core.h"
>>> +#include "qom/object.h"
>>> +#include "hw/irq.h"
>>> +
>>> +#define TYPE_PROXY_PIC "proxy-pic"
>>> +OBJECT_DECLARE_SIMPLE_TYPE(ProxyPICState, PROXY_PIC)
>>> +
>>> +#define MAX_PROXY_PIC_LINES 16
>>> +
>>> +/**
>>> + * This is a simple device which has 16 pairs of GPIO input and output 
>>> lines.
>>> + * Any change on an input line is forwarded to the respective output.
>>> + *
>>> + * QEMU interface:
>>> + *  + 16 unnamed GPIO inputs: the input lines
>>> + *  + 16 unnamed GPIO outputs: the output lines
>>> + */
>>
>>Re-reading this as a standalone patch, I can understand now why Phil was 
>>asking about device properties etc. because aside from the commit message, it 
>>isn't particularly clear that this is a workaround for QEMU's PIC devices and 
>>accelerator implementations not (yet) supporting direct wiring with qdev 
>>gpios. I would definitely argue that it is a special purpose and not a 
>>generic device.
>>
>>I apologise that this is quite late in the review process, however given that 
>>this wasn't immediately clear I do think it is worth making a few minor 
>>changes. Perhaps something like:
>>
>>- Update the comment above in proxy_pic.h clarifying that this is only for 
>>wiring up
>>  ISA PICs (similar to the commit message) until gpios can be used
>
>Will do.
>
>>- Move the .c and .h files from hw/core/proxy-pic.c and 
>>include/hw/core/proxy_pic.h
>>  to hw/i386/proxy-pic.c and include/hw/i386/proxy_pic.h to provide a strong 
>> hint
>>  that the device is restricted to x86-only
>
>The device gets used in PIIX4 as well, i.e. MIPS, too. I therefore think it is 
>not x86 but rather PIC specific. I propose to move it back to hw/intc/i8259 
>where it was implemented until v2: 
>https://patchew.org/QEMU/20221022150508.26830-1-shentey@gmail.com/20221022150508.26830-15-shentey@gmail.com/
> . I can also rename the device back to isa-pic to make things more obvious.

I've submitted v5 of the series. Mark, would you be available for review?

For Phil's convenience I've pushed a git tag here: 
https://github.com/shentok/qemu/commits/piix-consolidate-v5

Best regards,
Bernhard
>
>What do you think?
>
>Best regards,
>Bernhard
>
>>
>>I think this makes it more obvious what the device is doing, and also prevent 
>>its usage leaking into other places in the codebase. In fact in its current 
>>form there is no need for device properties to configure the PIC lines, since 
>>legacy x86 PICs always have 16 (ISA) IRQ lines.
>>
>>> +struct ProxyPICState {
>>> +    /*< private >*/
>>> +    struct DeviceState parent_obj;
>>> +    /*< public >*/
>>> +
>>> +    qemu_irq in_irqs[MAX_PROXY_PIC_LINES];
>>> +    qemu_irq out_irqs[MAX_PROXY_PIC_LINES];
>>> +};
>>> +
>>> +#endif /* HW_PROXY_PIC_H */
>>> diff --git a/hw/core/proxy-pic.c b/hw/core/proxy-pic.c
>>> new file mode 100644
>>> index 0000000000..40fd70b9e2
>>> --- /dev/null
>>> +++ b/hw/core/proxy-pic.c
>>> @@ -0,0 +1,54 @@
>>> +/*
>>> + * SPDX-License-Identifier: GPL-2.0-or-later
>>> + *
>>> + * Proxy interrupt controller device.
>>> + *
>>> + * Copyright (c) 2022 Bernhard Beschow <shentey@gmail.com>
>>> + */
>>> +
>>> +#include "qemu/osdep.h"
>>> +#include "hw/core/proxy-pic.h"
>>> +
>>> +static void proxy_pic_set_irq(void *opaque, int irq, int level)
>>> +{
>>> +    ProxyPICState *s = opaque;
>>> +
>>> +    qemu_set_irq(s->out_irqs[irq], level);
>>> +}
>>> +
>>> +static void proxy_pic_realize(DeviceState *dev, Error **errp)
>>> +{
>>> +    ProxyPICState *s = PROXY_PIC(dev);
>>> +
>>> +    qdev_init_gpio_in(DEVICE(s), proxy_pic_set_irq, MAX_PROXY_PIC_LINES);
>>> +    qdev_init_gpio_out(DEVICE(s), s->out_irqs, MAX_PROXY_PIC_LINES);
>>> +
>>> +    for (int i = 0; i < MAX_PROXY_PIC_LINES; ++i) {
>>> +        s->in_irqs[i] = qdev_get_gpio_in(DEVICE(s), i);
>>> +    }
>>> +}
>>> +
>>> +static void proxy_pic_class_init(ObjectClass *klass, void *data)
>>> +{
>>> +    DeviceClass *dc = DEVICE_CLASS(klass);
>>> +
>>> +    /* No state to reset or migrate */
>>> +    dc->realize = proxy_pic_realize;
>>> +
>>> +    /* Reason: Needs to be wired up to work */
>>> +    dc->user_creatable = false;
>>> +}
>>> +
>>> +static const TypeInfo proxy_pic_info = {
>>> +    .name          = TYPE_PROXY_PIC,
>>> +    .parent        = TYPE_DEVICE,
>>> +    .instance_size = sizeof(ProxyPICState),
>>> +    .class_init = proxy_pic_class_init,
>>> +};
>>> +
>>> +static void split_irq_register_types(void)
>>> +{
>>> +    type_register_static(&proxy_pic_info);
>>> +}
>>> +
>>> +type_init(split_irq_register_types)
>>> diff --git a/MAINTAINERS b/MAINTAINERS
>>> index 7a40d4d865..295a76bfbd 100644
>>> --- a/MAINTAINERS
>>> +++ b/MAINTAINERS
>>> @@ -1674,6 +1674,7 @@ S: Supported
>>>   F: hw/char/debugcon.c
>>>   F: hw/char/parallel*
>>>   F: hw/char/serial*
>>> +F: hw/core/proxy-pic.c
>>>   F: hw/dma/i8257*
>>>   F: hw/i2c/pm_smbus.c
>>>   F: hw/input/pckbd.c
>>> @@ -1690,6 +1691,7 @@ F: hw/watchdog/wdt_ib700.c
>>>   F: hw/watchdog/wdt_i6300esb.c
>>>   F: include/hw/display/vga.h
>>>   F: include/hw/char/parallel.h
>>> +F: include/hw/core/proxy-pic.h
>>>   F: include/hw/dma/i8257.h
>>>   F: include/hw/i2c/pm_smbus.h
>>>   F: include/hw/input/i8042.h
>>> diff --git a/hw/core/Kconfig b/hw/core/Kconfig
>>> index 9397503656..a7224f4ca0 100644
>>> --- a/hw/core/Kconfig
>>> +++ b/hw/core/Kconfig
>>> @@ -22,6 +22,9 @@ config OR_IRQ
>>>   config PLATFORM_BUS
>>>       bool
>>>   +config PROXY_PIC
>>> +    bool
>>> +
>>>   config REGISTER
>>>       bool
>>>   diff --git a/hw/core/meson.build b/hw/core/meson.build
>>> index 7a4d02b6c0..e86aef6ec3 100644
>>> --- a/hw/core/meson.build
>>> +++ b/hw/core/meson.build
>>> @@ -30,6 +30,7 @@ softmmu_ss.add(when: ['CONFIG_GUEST_LOADER', fdt], 
>>> if_true: files('guest-loader.
>>>   softmmu_ss.add(when: 'CONFIG_OR_IRQ', if_true: files('or-irq.c'))
>>>   softmmu_ss.add(when: 'CONFIG_PLATFORM_BUS', if_true: 
>>> files('platform-bus.c'))
>>>   softmmu_ss.add(when: 'CONFIG_PTIMER', if_true: files('ptimer.c'))
>>> +softmmu_ss.add(when: 'CONFIG_PROXY_PIC', if_true: files('proxy-pic.c'))
>>>   softmmu_ss.add(when: 'CONFIG_REGISTER', if_true: files('register.c'))
>>>   softmmu_ss.add(when: 'CONFIG_SPLIT_IRQ', if_true: files('split-irq.c'))
>>>   softmmu_ss.add(when: 'CONFIG_XILINX_AXI', if_true: files('stream.c'))
>>
>>
>>ATB,
>>
>>Mark.