Re: [PATCH v3] block: make BlockConf.*_size properties 32-bit

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 4/29/20 2:19 PM, Roman Kagan wrote:
> On Wed, Apr 29, 2020 at 11:41:04AM +0200, Philippe Mathieu-Daudé wrote:
>> Cc'ing virtio-blk and scsi maintainers.
>>
>> On 4/29/20 11:18 AM, Roman Kagan wrote:
>>> Devices (virtio-blk, scsi, etc.) and the block layer are happy to use
>>> 32-bit for logical_block_size, physical_block_size, and min_io_size.
>>> However, the properties in BlockConf are defined as uint16_t limiting
>>> the values to 32768.
>>>
>>> This appears unnecessary tight, and we've seen bigger block sizes handy
>>> at times.
>>>
>>> Make them 32 bit instead and lift the limitation up to 2 MiB which
>>> appears to be good enough for everybody, and matches the qcow2 cluster
>>> size limit.
>>>
>>> As the values can now be fairly big and awkward to type, make the
>>> property setter accept common size suffixes (k, m).
>>>
>>> Signed-off-by: Roman Kagan <rvkagan@yandex-team.ru>
>>> Reviewed-by: Eric Blake <eblake@redhat.com>
>>> ---
>>> v2 -> v3:
>>> - mention qcow2 cluster size limit in the log and comment [Eric]
>>>
>>> v1 -> v2:
>>> - cap the property at 2 MiB [Eric]
>>> - accept size suffixes
>>>
>>>    include/hw/block/block.h     |  8 ++++----
>>>    include/hw/qdev-properties.h |  2 +-
>>>    hw/core/qdev-properties.c    | 34 ++++++++++++++++++++++++----------
>>>    3 files changed, 29 insertions(+), 15 deletions(-)
>>>
>>> diff --git a/include/hw/block/block.h b/include/hw/block/block.h
>>> index d7246f3862..9dd6bba56a 100644
>>> --- a/include/hw/block/block.h
>>> +++ b/include/hw/block/block.h
>>> @@ -18,9 +18,9 @@
>>>    typedef struct BlockConf {
>>>        BlockBackend *blk;
>>> -    uint16_t physical_block_size;
>>> -    uint16_t logical_block_size;
>>> -    uint16_t min_io_size;
>>> +    uint32_t physical_block_size;
>>> +    uint32_t logical_block_size;
>>> +    uint32_t min_io_size;
>>>        uint32_t opt_io_size;
>>>        int32_t bootindex;
>>>        uint32_t discard_granularity;
>>> @@ -51,7 +51,7 @@ static inline unsigned int get_physical_block_exp(BlockConf *conf)
>>>                              _conf.logical_block_size),                    \
>>>        DEFINE_PROP_BLOCKSIZE("physical_block_size", _state,                \
>>>                              _conf.physical_block_size),                   \
>>> -    DEFINE_PROP_UINT16("min_io_size", _state, _conf.min_io_size, 0),    \
>>> +    DEFINE_PROP_UINT32("min_io_size", _state, _conf.min_io_size, 0),    \
>>>        DEFINE_PROP_UINT32("opt_io_size", _state, _conf.opt_io_size, 0),    \
>>>        DEFINE_PROP_UINT32("discard_granularity", _state,                   \
>>>                           _conf.discard_granularity, -1),                  \
>>> diff --git a/include/hw/qdev-properties.h b/include/hw/qdev-properties.h
>>> index f161604fb6..f9e0f8c041 100644
>>> --- a/include/hw/qdev-properties.h
>>> +++ b/include/hw/qdev-properties.h
>>> @@ -197,7 +197,7 @@ extern const PropertyInfo qdev_prop_pcie_link_width;
>>>    #define DEFINE_PROP_BIOS_CHS_TRANS(_n, _s, _f, _d) \
>>>        DEFINE_PROP_SIGNED(_n, _s, _f, _d, qdev_prop_bios_chs_trans, int)
>>>    #define DEFINE_PROP_BLOCKSIZE(_n, _s, _f) \
>>> -    DEFINE_PROP_UNSIGNED(_n, _s, _f, 0, qdev_prop_blocksize, uint16_t)
>>> +    DEFINE_PROP_UNSIGNED(_n, _s, _f, 0, qdev_prop_blocksize, uint32_t)
>>>    #define DEFINE_PROP_PCI_HOST_DEVADDR(_n, _s, _f) \
>>>        DEFINE_PROP(_n, _s, _f, qdev_prop_pci_host_devaddr, PCIHostDeviceAddress)
>>>    #define DEFINE_PROP_OFF_AUTO_PCIBAR(_n, _s, _f, _d) \
>>> diff --git a/hw/core/qdev-properties.c b/hw/core/qdev-properties.c
>>> index 2047114fca..e673f3c43f 100644
>>> --- a/hw/core/qdev-properties.c
>>> +++ b/hw/core/qdev-properties.c
>>> @@ -14,6 +14,7 @@
>>>    #include "qapi/visitor.h"
>>>    #include "chardev/char.h"
>>>    #include "qemu/uuid.h"
>>> +#include "qemu/units.h"
>>>    void qdev_prop_set_after_realize(DeviceState *dev, const char *name,
>>>                                      Error **errp)
>>> @@ -729,30 +730,42 @@ const PropertyInfo qdev_prop_pci_devfn = {
>>>    /* --- blocksize --- */
>>> +/* lower limit is sector size */
>>> +#define MIN_BLOCK_SIZE          512
>>> +#define MIN_BLOCK_SIZE_STR      "512 B"
>>> +/*
>>> + * upper limit is arbitrary, 2 MiB looks sufficient for all sensible uses, and
>>> + * matches qcow2 cluster size limit
>>> + */
>>> +#define MAX_BLOCK_SIZE          (2 * MiB)
>>> +#define MAX_BLOCK_SIZE_STR      "2 MiB"
>>> +
>>>    static void set_blocksize(Object *obj, Visitor *v, const char *name,
>>>                              void *opaque, Error **errp)
>>>    {
>>>        DeviceState *dev = DEVICE(obj);
>>>        Property *prop = opaque;
>>> -    uint16_t value, *ptr = qdev_get_prop_ptr(dev, prop);
>>> +    uint32_t *ptr = qdev_get_prop_ptr(dev, prop);
>>> +    uint64_t value;
>>>        Error *local_err = NULL;
>>> -    const int64_t min = 512;
>>> -    const int64_t max = 32768;
>>>        if (dev->realized) {
>>>            qdev_prop_set_after_realize(dev, name, errp);
>>>            return;
>>>        }
>>> -    visit_type_uint16(v, name, &value, &local_err);
>>> +    visit_type_size(v, name, &value, &local_err);
>>>        if (local_err) {
>>>            error_propagate(errp, local_err);
>>>            return;
>>>        }
>>>        /* value of 0 means "unset" */
>>> -    if (value && (value < min || value > max)) {
>>> -        error_setg(errp, QERR_PROPERTY_VALUE_OUT_OF_RANGE,
>>> -                   dev->id ? : "", name, (int64_t)value, min, max);
>>> +    if (value && (value < MIN_BLOCK_SIZE || value > MAX_BLOCK_SIZE)) {
>>> +        error_setg(errp,
>>> +                   "Property %s.%s doesn't take value %" PRIu64
>>> +                   " (minimum: " MIN_BLOCK_SIZE_STR
>>> +                   ", maximum: " MAX_BLOCK_SIZE_STR ")",
>>> +                   dev->id ? : "", name, value);
>>>            return;
>>>        }
>>> @@ -768,9 +781,10 @@ static void set_blocksize(Object *obj, Visitor *v, const char *name,
>>>    }
>>>    const PropertyInfo qdev_prop_blocksize = {
>>> -    .name  = "uint16",
>>> -    .description = "A power of two between 512 and 32768",
>>> -    .get   = get_uint16,
>>> +    .name  = "size",
>>> +    .description = "A power of two between " MIN_BLOCK_SIZE_STR
>>> +                   " and " MAX_BLOCK_SIZE_STR,
>>> +    .get   = get_uint32,
>>>        .set   = set_blocksize,
>>>        .set_default_value = set_default_value_uint,
>>>    };
>>>
>>
>> 1/ Don't you need to update SCSIBlockLimits too?
> 
> I guess you mean SCSIBlockLimits.min_io_size which is the only uint16_t
> field there, do you?

Yes.

> 
>> 2/ It seems hw/block/virtio-blk.c can get underflow now.
> 
> Both SCSIBlockLimits.min_io_size and virtio_blk_config.min_io_size are
> expressed in logical blocks so there appears to be no problem here.
> 
>> Maybe you miss this change:
>>
>> -- >8 --
>> diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
>> --- a/hw/block/virtio-blk.c
>> +++ b/hw/block/virtio-blk.c
>> @@ -917,7 +917,7 @@ static void virtio_blk_update_config(VirtIODevice *vdev,
>> uint8_t *config)
>>                    s->conf.seg_max_adjust ? s->conf.queue_size - 2 : 128 -
>> 2);
>>       virtio_stw_p(vdev, &blkcfg.geometry.cylinders, conf->cyls);
>>       virtio_stl_p(vdev, &blkcfg.blk_size, blk_size);
>> -    virtio_stw_p(vdev, &blkcfg.min_io_size, conf->min_io_size / blk_size);
>> +    virtio_stl_p(vdev, &blkcfg.min_io_size, conf->min_io_size / blk_size);
> 
> The width of this field in the device's config space is defined in the
> spec and can't be changed.
> 
> Nor is there any need due to this patch.

OK, thanks :)

> 
> Thanks,
> Roman.
> 
>>       virtio_stw_p(vdev, &blkcfg.opt_io_size, conf->opt_io_size / blk_size);
>>       blkcfg.geometry.heads = conf->heads;
>>       /*
>> ---
>>
>