Re: [Qemu-block] [PULL 2/5] block/nvme: support larger that 512 bytes sector devices

[Max Reitz]

On 29.07.19 15:16, Peter Maydell wrote:
> On Mon, 22 Jul 2019 at 18:26, Max Reitz <address@hidden> wrote:
>>
>> From: Maxim Levitsky <address@hidden>
>>
>> Currently the driver hardcodes the sector size to 512,
>> and doesn't check the underlying device. Fix that.
>>
>> Also fail if underlying nvme device is formatted with metadata
>> as this needs special support.
>>
>> Signed-off-by: Maxim Levitsky <address@hidden>
>> Message-id: address@hidden
>> Signed-off-by: Max Reitz <address@hidden>
> 
>> +static int64_t nvme_get_blocksize(BlockDriverState *bs)
>> +{
>> +    BDRVNVMeState *s = bs->opaque;
>> +    assert(s->blkshift >= BDRV_SECTOR_BITS);
>> +    return 1 << s->blkshift;
>> +}
> 
> Hi -- Coverity points out here that we calculate the
> "1 << s->blkshift" as a 32-bit shift, but then return an
> int64_t type (CID 1403771).
> 
> Can the blkshift ever really be 31 or more ?
> 
> The types here seem weird anyway -- we return an int64_t,
> but the only user of this is nvme_probe_blocksizes(),
> which uses the value only to set BlockSizes::phys and ::log,
> both of which are of type "uint32_t". That leads me to think
> that the right return type for the function is uint32_t.
> 
> PS: this is the only Coverity issue currently outstanding so
> if it's a trivial fix it might be nice to put it into rc3.

Maxim, what do you think?

How about we let nvme_identify() limit blkshift to something sane and
then return a uint32_t here?

In theory it would be limited by page_size, and that has a maximum value
of 2^27.  In practice, though, that limit is checked by another 32-bit
shift...

Max

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