Re: [PATCH v5 02/10] hw/fsi: Introduce IBM's scratchpad

[Ninad Palsule]

Hello Daniel,

On 10/19/23 03:20, Daniel P. Berrangé wrote:
> On Wed, Oct 11, 2023 at 10:13:31AM -0500, Ninad Palsule wrote:
> > This is a part of patchset where scratchpad is introduced.
> >
> > The scratchpad provides a set of non-functional registers. The firmware
> > is free to use them, hardware does not support any special management
> > support. The scratchpad registers can be read or written from LBUS
> > slave.
> >
> > In this model, The LBUS device is parent for the scratchpad.
> >
> > Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
> > Signed-off-by: Cédric Le Goater <clg@kaod.org>
> > Signed-off-by: Ninad Palsule <ninad@linux.ibm.com>
> > ---
> > v2:
> > - Incorporated Joel's review comments.
> > v5:
> > - Incorporated review comments by Cedric.
> > ---
> >   include/hw/fsi/engine-scratchpad.h | 33 ++++++++++
> >   hw/fsi/engine-scratchpad.c         | 99 ++++++++++++++++++++++++++++++
> >   hw/fsi/Kconfig                     |  4 ++
> >   hw/fsi/meson.build                 |  1 +
> >   hw/fsi/trace-events                |  2 +
> >   5 files changed, 139 insertions(+)
> >   create mode 100644 include/hw/fsi/engine-scratchpad.h
> >   create mode 100644 hw/fsi/engine-scratchpad.c
> >   create mode 100644 hw/fsi/trace-events
> >
> > diff --git a/include/hw/fsi/engine-scratchpad.h 
> > b/include/hw/fsi/engine-scratchpad.h
> > new file mode 100644
> > index 0000000000..17e9570c5c
> > --- /dev/null
> > +++ b/include/hw/fsi/engine-scratchpad.h
> > @@ -0,0 +1,33 @@
> > +/*
> > + * SPDX-License-Identifier: GPL-2.0-or-later
> > + * Copyright (C) 2023 IBM Corp.
> > + *
> > + * IBM scratchpad engne
> > + */
> > +#ifndef FSI_ENGINE_SCRATCHPAD_H
> > +#define FSI_ENGINE_SCRATCHPAD_H
> > +
> > +#include "qemu/bitops.h"
> > +
> > +#include "hw/fsi/lbus.h"
> > +
> > +#define ENGINE_CONFIG_NEXT              BE_BIT(0)
> > +#define ENGINE_CONFIG_VPD               BE_BIT(1)
> > +#define ENGINE_CONFIG_SLOTS             BE_GENMASK(8, 15)
> > +#define ENGINE_CONFIG_VERSION           BE_GENMASK(16, 19)
> > +#define ENGINE_CONFIG_TYPE              BE_GENMASK(20, 27)
> > +#define   ENGINE_CONFIG_TYPE_PEEK       (0x02 << 4)
> > +#define   ENGINE_CONFIG_TYPE_FSI        (0x03 << 4)
> > +#define   ENGINE_CONFIG_TYPE_SCRATCHPAD (0x06 << 4)
> > +#define ENGINE_CONFIG_CRC              BE_GENMASK(28, 31)
> > +
> > +#define TYPE_SCRATCHPAD "scratchpad"
> > +#define SCRATCHPAD(obj) OBJECT_CHECK(ScratchPad, (obj), TYPE_SCRATCHPAD)
> > +
> > +typedef struct ScratchPad {
> > +        FSILBusDevice parent;
> > +
> > +        uint32_t reg;
> > +} ScratchPad;
> > +
> > +#endif /* FSI_ENGINE_SCRATCHPAD_H */
> > diff --git a/hw/fsi/engine-scratchpad.c b/hw/fsi/engine-scratchpad.c
> > new file mode 100644
> > index 0000000000..60f678eec4
> > --- /dev/null
> > +++ b/hw/fsi/engine-scratchpad.c
> > @@ -0,0 +1,99 @@
> > +/*
> > + * SPDX-License-Identifier: GPL-2.0-or-later
> > + * Copyright (C) 2023 IBM Corp.
> > + *
> > + * IBM scratchpad engine
> > + */
> > +
> > +#include "qemu/osdep.h"
> > +
> > +#include "qapi/error.h"
> > +#include "qemu/log.h"
> > +#include "trace.h"
> > +
> > +#include "hw/fsi/engine-scratchpad.h"
> > +
> > +static uint64_t scratchpad_read(void *opaque, hwaddr addr, unsigned size)
> > +{
> > +    ScratchPad *s = SCRATCHPAD(opaque);
> > +
> > +    trace_scratchpad_read(addr, size);
> > +
> > +    if (addr) {
> > +        qemu_log_mask(LOG_GUEST_ERROR,
> > +                      "%s: Out of bounds read: 0x%"HWADDR_PRIx" for %u\n",
> > +                      __func__, addr, size);
> We already have a trace point in the line above. I don't think we should
> be unconditionally logging errors like this, as this becomes a guest
> triggerable denial of service on the host log collector for the guest.
> eg it could flood the logfile connected to stderr with unlimited data
> by repeatedly doing bad reads/writes.
Make sense. We can catch it using the existing traces. I have removed it 
from read and write function.
> > +        return 0;
> > +    }
> > +
> > +    return s->reg;
> > +}
> > +
> > +static void scratchpad_write(void *opaque, hwaddr addr, uint64_t data,
> > +                                 unsigned size)
> > +{
> > +    ScratchPad *s = SCRATCHPAD(opaque);
> > +
> > +    trace_scratchpad_write(addr, size, data);
> > +
> > +    if (addr) {
> > +        qemu_log_mask(LOG_GUEST_ERROR,
> > +                      "%s: Out of bounds write: 0x%"HWADDR_PRIx" for %u\n",
> > +                      __func__, addr, size);
> > +        return;
> > +    }
> > +
> > +    s->reg = data;
> > +}
> > +
> > +static const struct MemoryRegionOps scratchpad_ops = {
> > +    .read = scratchpad_read,
> > +    .write = scratchpad_write,
> > +    .endianness = DEVICE_BIG_ENDIAN,
> > +};
> > +
> > +static void scratchpad_realize(DeviceState *dev, Error **errp)
> > +{
> > +    FSILBusDevice *ldev = FSI_LBUS_DEVICE(dev);
> > +
> > +    memory_region_init_io(&ldev->iomem, OBJECT(ldev), &scratchpad_ops,
> > +                          ldev, TYPE_SCRATCHPAD, 0x400);
> > +}
> > +
> > +static void scratchpad_reset(DeviceState *dev)
> > +{
> > +    ScratchPad *s = SCRATCHPAD(dev);
> > +
> > +    s->reg = 0;
> > +}
> > +
> > +static void scratchpad_class_init(ObjectClass *klass, void *data)
> > +{
> > +    DeviceClass *dc = DEVICE_CLASS(klass);
> > +    FSILBusDeviceClass *ldc = FSI_LBUS_DEVICE_CLASS(klass);
> > +
> > +    dc->realize = scratchpad_realize;
> > +    dc->reset = scratchpad_reset;
> > +
> > +    ldc->config =
> > +          ENGINE_CONFIG_NEXT            /* valid */
> > +        | 0x00010000                    /* slots */
> > +        | 0x00001000                    /* version */
> > +        | ENGINE_CONFIG_TYPE_SCRATCHPAD /* type */
> > +        | 0x00000007;                   /* crc */
> More common QEMU style would be for the "|" to be on the end
> of line rather than start.
>
> End of line:
>
> $ git grep '.*\s|\s*$' "*.c" | wc -l
> 5381
>
> Start of line:
>
> $ git grep '^\s*|\s.*' "*.c" | wc -l
> 581

Fixed as per you suggestion.

Thanks for the review.

Regards,

Ninad

> > +}
> > +
> > +static const TypeInfo scratchpad_info = {
> > +    .name = TYPE_SCRATCHPAD,
> > +    .parent = TYPE_FSI_LBUS_DEVICE,
> > +    .instance_size = sizeof(ScratchPad),
> > +    .class_init = scratchpad_class_init,
> > +    .class_size = sizeof(FSILBusDeviceClass),
> > +};
> > +
> > +static void scratchpad_register_types(void)
> > +{
> > +    type_register_static(&scratchpad_info);
> > +}
> > +
> > +type_init(scratchpad_register_types);
> > diff --git a/hw/fsi/Kconfig b/hw/fsi/Kconfig
> > index e650c660f0..f7c7fd1b28 100644
> > --- a/hw/fsi/Kconfig
> > +++ b/hw/fsi/Kconfig
> > @@ -1,2 +1,6 @@
> > +config FSI_SCRATCHPAD
> > +    bool
> > +    select FSI_LBUS
> > +
> >   config FSI_LBUS
> >       bool
> > diff --git a/hw/fsi/meson.build b/hw/fsi/meson.build
> > index 4074d3a7d2..d45a98c223 100644
> > --- a/hw/fsi/meson.build
> > +++ b/hw/fsi/meson.build
> > @@ -1 +1,2 @@
> >   system_ss.add(when: 'CONFIG_FSI_LBUS', if_true: files('lbus.c'))
> > +system_ss.add(when: 'CONFIG_FSI_SCRATCHPAD', if_true: 
> > files('engine-scratchpad.c'))
> > diff --git a/hw/fsi/trace-events b/hw/fsi/trace-events
> > new file mode 100644
> > index 0000000000..97fd070354
> > --- /dev/null
> > +++ b/hw/fsi/trace-events
> > @@ -0,0 +1,2 @@
> > +scratchpad_read(uint64_t addr, uint32_t size) "@0x%" PRIx64 " size=%d"
> > +scratchpad_write(uint64_t addr, uint32_t size, uint64_t data) "@0x%" PRIx64 " 
> > size=%d value=0x%"PRIx64
> > --
> > 2.39.2
> With regards,
> Daniel