On 2018-09-25 17:37, David Hildenbrand wrote:
> On 25/09/2018 17:20, Thomas Huth wrote:
>> The IplParameterBlock and QemuIplParameters structures are declared
>> with QEMU_PACKED, so the compiler assumes that the structures do not
>> need to be aligned in memory. Since the are listed after a "bool"
>> within the S390IPLState, the IplParameterBlock and QemuIplParameters
>> are also indeed mis-aligned in memory. This causes problems on Sparc
>> during migration, since we use VMSTATE_UINT16 in vmstate_iplb to access
>> the devno member for example, and the corresponding migration functions
>> (like qemu_get_be16s) then try to access a 16-bit value from a mis-
>> aligned memory address.
>> The easiest solution to fix this problem is to move the packed structures
>> to the beginning of the S390IPLState. Also add some additional comments
>> here to prevent that this problem will be introduced again in the future.
>>
>> Signed-off-by: Thomas Huth <th...@redhat.com>
>> ---
>> hw/s390x/ipl.h | 6 ++++--
>> 1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/hw/s390x/ipl.h b/hw/s390x/ipl.h
>> index 4e87b89..f72a82f 100644
>> --- a/hw/s390x/ipl.h
>> +++ b/hw/s390x/ipl.h
>> @@ -132,15 +132,17 @@ typedef struct QemuIplParameters QemuIplParameters;
>> struct S390IPLState {
>> /*< private >*/
>> DeviceState parent_obj;
>> + /* Packed structs first (to make sure we've got a proper alignment): */
>
> Is that a sad smiley at the end? ;)
>
>> + IplParameterBlock iplb;
>> + QemuIplParameters qipl;
>> + /* Other private members without packed attribute: */
>> uint64_t start_addr;
>> uint64_t compat_start_addr;
>> uint64_t bios_start_addr;
>> uint64_t compat_bios_start_addr;
>> bool enforce_bios;
>> - IplParameterBlock iplb;
>> bool iplb_valid;
>> bool netboot;
>> - QemuIplParameters qipl;
>> /* reset related properties don't have to be migrated or reset */
>> enum s390_reset reset_type;
>> int reset_cpu_index;
>>
>
> Instead of the comment, compile time asserts using offsetof?
Good idea, let's do that instead!
Thomas
