Re: [PATCH 08/18] pc-bios/s390-ccw: Remove panics from ECKD IPL path

[Jared Rossi <jrossi@linux.ibm.com>]

On 9/27/24 11:29 AM, Thomas Huth wrote:
> On 27/09/2024 02.51, jrossi@linux.ibm.com wrote:
>> From: Jared Rossi <jrossi@linux.ibm.com>
>>
>> Remove panic-on-error from ECKD block device IPL specific functions 
>> so that
>> error recovery may be possible in the future.
>>
>> Functions that would previously panic now provide a return code.
>>
>> Signed-off-by: Jared Rossi <jrossi@linux.ibm.com>
>>
>> ---
>>   pc-bios/s390-ccw/bootmap.c | 183 +++++++++++++++++++++++++------------
>>   1 file changed, 125 insertions(+), 58 deletions(-)
>>
>> diff --git a/pc-bios/s390-ccw/bootmap.c b/pc-bios/s390-ccw/bootmap.c
>> index 0751a225cd..dc7200c264 100644
>> --- a/pc-bios/s390-ccw/bootmap.c
>> +++ b/pc-bios/s390-ccw/bootmap.c
>> @@ -145,14 +145,17 @@ static block_number_t 
>> load_eckd_segments(block_number_t blk, bool ldipl,
>>       bool more_data;
>>         memset(_bprs, FREE_SPACE_FILLER, sizeof(_bprs));
>> -    read_block(blk, bprs, "BPRS read failed");
>> +    if (virtio_read(blk, bprs)) {
>> +        puts("BPRS read failed");
>> +        return -EIO;
>> +    }
>>         do {
>>           more_data = false;
>>           for (j = 0;; j++) {
>>               block_nr = gen_eckd_block_num(&bprs[j].xeckd, ldipl);
>>               if (is_null_block_number(block_nr)) { /* end of chunk */
>> -                break;
>> +                return 0; /* use 0 to indicate end of load, not real 
>> block 0 */
>
> Can we be very sure that block 0 is never a valid one, so that 
> returning 0 is OK here? Maybe you could use an error code instead 
> (intruducing e.g. ENOENT ?)

Yes, because block 0 is an administrative block and is reserved in both CDL
and LDL disk formats.  That being said, it is simple enough to use a 
specific
RC instead, which would be more resilient to format changes in the future
(e.g. if CDL and LDL are no longer written for list-directed IPL formatted
disks), so it is probably worth while to add a new code as you suggest.