Re: [Qemu-devel] [PATCH v3 5/5] s390x/css: support ccw IDA

[Halil Pasic <pasic@linux.vnet.ibm.com>]

On 09/20/2017 10:11 AM, Cornelia Huck wrote:
> On Tue, 19 Sep 2017 20:27:45 +0200
> Halil Pasic <pasic@linux.vnet.ibm.com> wrote:
> 
>> Let's add indirect data addressing support for our virtual channel
>> subsystem. This implementation does not bother with any kind of
>> prefetching. We simply step through the IDAL on demand.
>>
>> Signed-off-by: Halil Pasic <pasic@linux.vnet.ibm.com>
>> Signed-off-by: Cornelia Huck <cohuck@redhat.com>
> 
> My s-o-b is a bit preliminary ;)
> 
>> ---
>>  hw/s390x/css.c | 117 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
>>  1 file changed, 116 insertions(+), 1 deletion(-)
>>
>> diff --git a/hw/s390x/css.c b/hw/s390x/css.c
>> index 2d37a9ddde..a3ce6d89b6 100644
>> --- a/hw/s390x/css.c
>> +++ b/hw/s390x/css.c
>> @@ -827,6 +827,121 @@ incr:
>>      return 0;
>>  }
>>  
>> +/* returns values between 1 and bsz, where bsz is a power of 2 */
>> +static inline uint16_t ida_continuous_left(hwaddr cda, uint64_t bsz)
>> +{
>> +    return bsz - (cda & (bsz - 1));
>> +}
>> +
>> +static inline uint64_t ccw_ida_block_size(uint8_t flags)
>> +{
>> +    if ((flags & CDS_F_C64) && !(flags & CDS_F_I2K)) {
>> +        return 1ULL << 12;
>> +    }
>> +    return 1ULL << 11;
>> +}
>> +
>> +static inline int ida_read_next_idaw(CcwDataStream *cds, bool ccw_fmt1,
>> +                                     bool idaw_fmt_2)
>> +{
>> +    union {uint64_t fmt2; uint32_t fmt1; } idaw;
>> +    int ret;
>> +    hwaddr idaw_addr;
>> +
>> +    if (idaw_fmt_2) {
>> +        idaw_addr = cds->cda_orig + sizeof(idaw.fmt2) * cds->at_idaw;
>> +        if (idaw_addr & 0x07 && cds_ccw_addrs_ok(idaw_addr, 0, ccw_fmt1)) {
> 
> So, what is supposed to happen if the idaw_addr is not aligned
> correctly _and_ is violating the limits?

You are right this is obviously wrong.

Should have been 
if (idaw_addr & 0x07 || !cds_ccw_addrs_ok(idaw_addr, 0, ccw_fmt1)) {

> 
>> +            return -EINVAL; /* channel program check */
>> +        }
>> +        ret = address_space_rw(&address_space_memory, idaw_addr,
>> +                               MEMTXATTRS_UNSPECIFIED, (void *) &idaw.fmt2,
>> +                               sizeof(idaw.fmt2), false);
>> +        cds->cda = be64_to_cpu(idaw.fmt2);
>> +    } else {
>> +        idaw_addr = cds->cda_orig + sizeof(idaw.fmt1) * cds->at_idaw;
>> +        if (idaw_addr & 0x03 && cds_ccw_addrs_ok(idaw_addr, 0, ccw_fmt1)) {

Same here.

>> +            return -EINVAL; /* channel program check */
>> +        }
>> +        ret = address_space_rw(&address_space_memory, idaw_addr,
>> +                               MEMTXATTRS_UNSPECIFIED, (void *) &idaw.fmt1,
>> +                               sizeof(idaw.fmt1), false);
>> +        cds->cda = be64_to_cpu(idaw.fmt1);
>> +    }
>> +    ++(cds->at_idaw);
>> +    if (ret != MEMTX_OK) {
>> +        /* assume inaccessible address */
>> +        return -EINVAL; /* channel program check */
>> +
>> +    }
>> +    return 0;
>> +}
>