On 25 September 2018 at 17:14, Cornelia Huck <coh...@redhat.com> wrote: > On Tue, 25 Sep 2018 17:20:08 +0200 > Thomas Huth <th...@redhat.com> wrote: > >> The uint16_t member cu_type of struct SenseId is not naturally aligned, >> and since the struct is marked with QEMU_PACKED, this can lead to >> unaligned memory accesses - which does not work on architectures like >> Sparc. Thus remove the QEMU_PACKED here and rather copy the struct >> byte by byte when we do copy_sense_id_to_guest(). > > Hm... would it look nicer if we chopped up {cu,dev}_type into a hi/lo > byte and keep the QEMU_PACKED? (The ciws should be ok, I think.)
>> -static void copy_sense_id_to_guest(SenseId *dest, SenseId *src) >> +static void copy_sense_id_to_guest(uint8_t *dest, SenseId *src) >> { >> int i; >> >> - dest->reserved = src->reserved; >> - dest->cu_type = cpu_to_be16(src->cu_type); >> - dest->cu_model = src->cu_model; >> - dest->dev_type = cpu_to_be16(src->dev_type); >> - dest->dev_model = src->dev_model; >> - dest->unused = src->unused; >> - for (i = 0; i < ARRAY_SIZE(dest->ciw); i++) { >> - dest->ciw[i].type = src->ciw[i].type; >> - dest->ciw[i].command = src->ciw[i].command; >> - dest->ciw[i].count = cpu_to_be16(src->ciw[i].count); >> + dest[0] = src->reserved; >> + dest[1] = src->cu_type >> 8; >> + dest[2] = src->cu_type & 0xff; >> + dest[3] = src->cu_model; >> + dest[4] = src->dev_type >> 8; >> + dest[5] = src->dev_type & 0xff; >> + dest[6] = src->dev_model; >> + dest[7] = src->unused; >> + for (i = 0; i < ARRAY_SIZE(src->ciw); i++) { >> + dest[8 + i * 4] = src->ciw[i].type; >> + dest[9 + i * 4] = src->ciw[i].command; >> + dest[10 + i * 4] = src->ciw[i].count >> 8; >> + dest[11 + i * 4] = src->ciw[i].count & 0xff; > > /me gets a headache while trying to understand the endianness here... Possibly easier to understand written as: stw_be_p(dest + 10 + i * 4, src->ciw[i].count); (There is also an stb_p(ptr, value) if you want all the filling in of the dest buffer here to look consistent, though it doesn't do anything more magical than *(uint8_t *)ptr = value.) thanks -- PMM