On 05.04.2018 17:11, David Hildenbrand wrote:
> On 05.04.2018 17:07, Viktor Mihajlovski wrote:
>> IPL over a virtio-scsi device requires special handling not
>> available in the real architecture. For this purpose the IPL
>> type 0xFF has been chosen as means of communication between
>> QEMU and the pc-bios. However, a guest OS could be confused
>> by seeing an unknown IPL type.
>>
>> This change sets the IPL parameter type to 0x02 (CCW) to prevent
>> this. Pre-existing Linux has looked up the IPL parameters only in
>> the case of FCP IPL. This means that the behavior should stay
>> the same even if Linux checks for the IPL type unconditionally.
>>
>> Signed-off-by: Viktor Mihajlovski <mihaj...@linux.vnet.ibm.com>
>> ---
>> pc-bios/s390-ccw/bootmap.c | 7 +++++++
>> pc-bios/s390-ccw/iplb.h | 15 +++++++++++++--
>> 2 files changed, 20 insertions(+), 2 deletions(-)
>>
>> diff --git a/pc-bios/s390-ccw/bootmap.c b/pc-bios/s390-ccw/bootmap.c
>> index fc2a9fe..9287b7a 100644
>> --- a/pc-bios/s390-ccw/bootmap.c
>> +++ b/pc-bios/s390-ccw/bootmap.c
>> @@ -70,6 +70,13 @@ static void jump_to_IPL_code(uint64_t address)
>> {
>> /* store the subsystem information _after_ the bootmap was loaded */
>> write_subsystem_identification();
>> +
>> + /* prevent unknown IPL types in the guest */
>> + if (iplb.pbt == S390_IPL_TYPE_QEMU_SCSI) {
>> + iplb.pbt = S390_IPL_TYPE_CCW;
>> + set_iplb(&iplb);
>> + }
>
> Confused, doesn't this imply that a system reset immediately after this
> instruction will result in something different getting booted?
>
Not if the other (QEMU) patches of this series are applied. Without
them, the behavior is the same as with an re-ipl (Today's Linux will
always request a CCW re-ipl).
[...]
--
Regards,
Viktor Mihajlovski
