Re: [PATCH v4 3/3] block: make BlockConf.*_size properties 32-bit

[Roman Kagan <rvkagan@yandex-team.ru>]

On Wed, May 20, 2020 at 11:04:44AM +0200, Philippe Mathieu-Daudé wrote:
> On 5/20/20 10:06 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).
> > 
> > Also as the devices which use min_io_size (virtio-blk and scsi) pass its
> > value to the guest in units of logical blocks in a 16bit field, to
> > prevent its silent truncation add a corresponding check to
> > blkconf_blocksizes.
> > 
> > Signed-off-by: Roman Kagan <rvkagan@yandex-team.ru>
> > ---
> > v3 -> v4:
> > - check min_io_size against truncation [Kevin]
> > 
> > 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/block/block.c             | 11 +++++++++++
> >   hw/core/qdev-properties.c    | 34 ++++++++++++++++++++++++----------
> >   4 files changed, 40 insertions(+), 15 deletions(-)
> > 
> > diff --git a/include/hw/block/block.h b/include/hw/block/block.h
> > index 784953a237..2fa09aa0b1 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/block/block.c b/hw/block/block.c
> > index 5f8ebff59c..cd95e7e38f 100644
> > --- a/hw/block/block.c
> > +++ b/hw/block/block.c
> > @@ -96,6 +96,17 @@ bool blkconf_blocksizes(BlockConf *conf, Error **errp)
> >           return false;
> >       }
> > +    /*
> > +     * all devices which support min_io_size (scsi and virtio-blk) expose it to
> > +     * the guest as a uint16_t in units of logical blocks
> > +     */
> > +    if ((conf->min_io_size / conf->logical_block_size) > UINT16_MAX) {
> > +        error_setg(errp,
> > +                   "min_io_size must be no more than " stringify(UINT16_MAX)
> > +                   " of logical_block_size");
> > +        return false;
> > +    }
> > +
> >       if (conf->opt_io_size % conf->logical_block_size) {
> >           error_setg(errp,
> >                      "opt_io_size must be a multple of logical_block_size");
> > diff --git a/hw/core/qdev-properties.c b/hw/core/qdev-properties.c
> > index cc924815da..fd03cc7597 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)
> 
> Can you split this patch?
> 
> - add/use definitions (here MAX_BLOCK_SIZE = 32 * KiB)
> - use 32-bit
> - raise limit to 2MB

I can see the value of splitting out the rework of the blocksize
property, but I'm struggling to justify expanding the fields without
increasing the limits.  Do you mind if I do it in two patches rather
than three?

Thanks,
Roman.

> 
> Feel free to refuse, but having atomic changes is better for bisectability
> and cherry-picking/reverting.
> 
> Thanks,
> 
> Phil.
> 
> > +#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,
> >   };
> > 
>