Re: [PATCH for-5.0 v11 12/20] qapi: Introduce DEFINE_PROP_INTERVAL

[Markus Armbruster <armbru@redhat.com>]

Eric Auger <eric.auger@redhat.com> writes:

> Introduce a new property defining a labelled interval:
> <low address>,<high address>,label.
>
> This will be used to encode reserved IOVA regions. The label
> is left undefined to ease reuse accross use cases.

What does the last sentence mean?

> For instance, in virtio-iommu use case, reserved IOVA regions
> will be passed by the machine code to the virtio-iommu-pci
> device (an array of those). The label will match the
> virtio_iommu_probe_resv_mem subtype value:
> - VIRTIO_IOMMU_RESV_MEM_T_RESERVED (0)
> - VIRTIO_IOMMU_RESV_MEM_T_MSI (1)
>
> This is used to inform the virtio-iommu-pci device it should
> bypass the MSI region: 0xfee00000, 0xfeefffff, 1.

So the "label" part of "<low address>,<high address>,label" is a number?

Is a number appropriate for your use case, or would an enum be better?

>
> Signed-off-by: Eric Auger <eric.auger@redhat.com> ---
>hw/core/qdev-properties.c | 90 ++++++++++++++++++++++++++++++++++++
>include/exec/memory.h | 6 +++ include/hw/qdev-properties.h | 3 ++
>include/qemu/typedefs.h | 1 + 4 files changed, 100 insertions(+)

Subject has 'qapi:', but it's actually about qdev.  Please adjust the subject.

> diff --git a/hw/core/qdev-properties.c b/hw/core/qdev-properties.c
> index ac28890e5a..8d70f34e37 100644
> --- a/hw/core/qdev-properties.c
> +++ b/hw/core/qdev-properties.c
> @@ -13,6 +13,7 @@
>  #include "qapi/visitor.h"
>  #include "chardev/char.h"
>  #include "qemu/uuid.h"
> +#include "qemu/cutils.h"
>  
>  void qdev_prop_set_after_realize(DeviceState *dev, const char *name,
>                                    Error **errp)
> @@ -585,6 +586,95 @@ const PropertyInfo qdev_prop_macaddr = {
>      .set   = set_mac,
>  };
>  
> +/* --- Labelled Interval --- */
> +
> +/*
> + * accepted syntax versions:

"versions"?

> + *   <low address>,<high address>,<type>
> + *   where low/high addresses are uint64_t in hexa (feat. 0x prefix)

"hexa" is not a word.

I'm afraid I don't get the parenthesis.

> + *   and type is an unsigned integer
> + */
> +static void get_interval(Object *obj, Visitor *v, const char *name,
> +                         void *opaque, Error **errp)
> +{
> +    DeviceState *dev = DEVICE(obj);
> +    Property *prop = opaque;
> +    Interval *interval = qdev_get_prop_ptr(dev, prop);
> +    char buffer[64];
> +    char *p = buffer;
> +
> +    Snprintf(buffer, sizeof(buffer), "0x%"PRIx64",0x%"PRIx64",%d",
> +             interval->low, interval->high, interval->type);

interval->type is unsigned.  Use %u, not %d.

> +
> +    visit_type_str(v, name, &p, errp);
> +}
> +
> +static void set_interval(Object *obj, Visitor *v, const char *name,
> +                         void *opaque, Error **errp)
> +{
> +    DeviceState *dev = DEVICE(obj);
> +    Property *prop = opaque;
> +    Interval *interval = qdev_get_prop_ptr(dev, prop);
> +    Error *local_err = NULL;
> +    unsigned int type;
> +    gchar **fields;
> +    uint64_t addr;
> +    char *str;
> +    int ret;
> +
> +    if (dev->realized) {
> +        qdev_prop_set_after_realize(dev, name, errp);
> +        return;
> +    }
> +
> +    visit_type_str(v, name, &str, &local_err);
> +    if (local_err) {
> +        error_propagate(errp, local_err);
> +        return;
> +    }
> +
> +    fields = g_strsplit(str, ",", 3);
> +
> +    ret = qemu_strtou64(fields[0], NULL, 16, &addr);

Aha, the 0x prefix is actually optional.

> +    if (!ret) {
> +        interval->low = addr;
> +    } else {
> +        error_setg(errp, "Failed to decode interval low addr");
> +        error_append_hint(errp,
> +                          "should be an address in hexa with 0x prefix\n");

"hexa" is not a word, and the 0x prefix is actually optional.

> +        goto out;
> +    }

I prefer

       if (error) {
           handle error
           bail out
       }
       handle success

over

       if (success) {
           handle success
       if (error) {
           handle error
           bail out
       }

In this case:

       if (ret) {
           error_setg(errp, "Failed to decode interval low addr");
           error_append_hint(errp,
                             "should be an address in hexa with 0x prefix\n");
           goto out;
       }
       interval->low = addr;


> +
> +    ret = qemu_strtou64(fields[1], NULL, 16, &addr);

Crash if @str doesn't contain ',', because the g_strsplit(str, ",", 3)
yields { [0] = str, NULL }.

> +    if (!ret) {
> +        interval->high = addr;
> +    } else {
> +        error_setg(errp, "Failed to decode interval high addr");
> +        error_append_hint(errp,
> +                          "should be an address in hexa with 0x prefix\n");
> +        goto out;
> +    }
> +
> +    ret = qemu_strtoui(fields[2], NULL, 10, &type);

Likewise, crash if @str contains only one ','.

I wouldn't use g_strsplit() here.  After

    ret = qemu_strtoui(str, &endptr, 16, &interval->low);

@endptr points behind the address.  So:

    if (ret || *endptr != ',') {
        handle error ...
        goto out
    }

    ret = qemu_strtoui(endptr + 1, &endptr, 16, &interval->high);

and so forth.

Note that the if (ret || *endptr != ',') checks for two distinct errors.
Distinct error messages might be more helpful.

> +    if (!ret) {
> +        interval->type = type;
> +    } else {
> +        error_setg(errp, "Failed to decode interval type");
> +        error_append_hint(errp, "should be an unsigned int in decimal\n");
> +    }
> +out:
> +    g_free(str);
> +    g_strfreev(fields);
> +    return;
> +}
> +
> +const PropertyInfo qdev_prop_interval = {
> +    .name  = "labelled_interval",
> +    .description = "Labelled interval, example: 0xFEE00000,0xFEEFFFFF,0",
> +    .get   = get_interval,
> +    .set   = set_interval,
> +};
> +
>  /* --- on/off/auto --- */
>  
>  const PropertyInfo qdev_prop_on_off_auto = {
> diff --git a/include/exec/memory.h b/include/exec/memory.h
> index e499dc215b..e238d1c352 100644
> --- a/include/exec/memory.h
> +++ b/include/exec/memory.h
> @@ -57,6 +57,12 @@ struct MemoryRegionMmio {
>      CPUWriteMemoryFunc *write[3];
>  };
>  
> +struct Interval {
> +    hwaddr low;
> +    hwaddr high;
> +    unsigned int type;
> +};

This isn't an interval.  An interval consists of two values, not three.

The third one is called "type" here, and "label" elsewhere.  Pick one
and stick to it.

Then pick a name for the triple.  Elsewhere, you call it "labelled
interval".

> +
>  typedef struct IOMMUTLBEntry IOMMUTLBEntry;
>  
>  /* See address_space_translate: bit 0 is read, bit 1 is write.  */
> diff --git a/include/hw/qdev-properties.h b/include/hw/qdev-properties.h
> index c6a8cb5516..2ba7c8711b 100644
> --- a/include/hw/qdev-properties.h
> +++ b/include/hw/qdev-properties.h
> @@ -20,6 +20,7 @@ extern const PropertyInfo qdev_prop_chr;
>  extern const PropertyInfo qdev_prop_tpm;
>  extern const PropertyInfo qdev_prop_ptr;
>  extern const PropertyInfo qdev_prop_macaddr;
> +extern const PropertyInfo qdev_prop_interval;
>  extern const PropertyInfo qdev_prop_on_off_auto;
>  extern const PropertyInfo qdev_prop_losttickpolicy;
>  extern const PropertyInfo qdev_prop_blockdev_on_error;
> @@ -202,6 +203,8 @@ extern const PropertyInfo qdev_prop_pcie_link_width;
>      DEFINE_PROP(_n, _s, _f, qdev_prop_drive_iothread, BlockBackend *)
>  #define DEFINE_PROP_MACADDR(_n, _s, _f)         \
>      DEFINE_PROP(_n, _s, _f, qdev_prop_macaddr, MACAddr)
> +#define DEFINE_PROP_INTERVAL(_n, _s, _f)         \
> +    DEFINE_PROP(_n, _s, _f, qdev_prop_interval, Interval)
>  #define DEFINE_PROP_ON_OFF_AUTO(_n, _s, _f, _d) \
>      DEFINE_PROP_SIGNED(_n, _s, _f, _d, qdev_prop_on_off_auto, OnOffAuto)
>  #define DEFINE_PROP_LOSTTICKPOLICY(_n, _s, _f, _d) \
> diff --git a/include/qemu/typedefs.h b/include/qemu/typedefs.h
> index 375770a80f..a827c9a3fe 100644
> --- a/include/qemu/typedefs.h
> +++ b/include/qemu/typedefs.h
> @@ -58,6 +58,7 @@ typedef struct ISABus ISABus;
>  typedef struct ISADevice ISADevice;
>  typedef struct IsaDma IsaDma;
>  typedef struct MACAddr MACAddr;
> +typedef struct Interval Interval;
>  typedef struct MachineClass MachineClass;
>  typedef struct MachineState MachineState;
>  typedef struct MemoryListener MemoryListener;