Re: [kvm-unit-tests PATCH v4 2/2] s390x: sclp: Implement SCLP_RC_INSUFFICIENT_SCCB_LENGTH

[Pierre Morel <pmorel@linux.ibm.com>]

On 5/30/23 17:35, Claudio Imbrenda wrote:
> On Tue, 30 May 2023 14:52:43 +0200
> Pierre Morel <pmorel@linux.ibm.com> wrote:
>
>> If SCLP_CMDW_READ_SCP_INFO fails due to a short buffer, retry
>> with a greater buffer.
> the idea is good, but I wonder if the code can be simplified (see below)
>
>> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
>> ---
>>   lib/s390x/sclp.c | 58 +++++++++++++++++++++++++++++++++++++++++-------
>>   1 file changed, 50 insertions(+), 8 deletions(-)
>>
>> diff --git a/lib/s390x/sclp.c b/lib/s390x/sclp.c
>> index 34a31da..9d51ca4 100644
>> --- a/lib/s390x/sclp.c
>> +++ b/lib/s390x/sclp.c
>> @@ -17,13 +17,14 @@
>>   #include "sclp.h"
>>   #include <alloc_phys.h>
>>   #include <alloc_page.h>
>> +#include <asm/facility.h>
>>   
>>   extern unsigned long stacktop;
>>   
>>   static uint64_t storage_increment_size;
>>   static uint64_t max_ram_size;
>>   static uint64_t ram_size;
>> -char _read_info[PAGE_SIZE] __attribute__((__aligned__(PAGE_SIZE)));
>> +char _read_info[2 * PAGE_SIZE] __attribute__((__aligned__(PAGE_SIZE)));
> this is ok ^
>
> [skip everything else]
>
>>   void sclp_read_info(void)
>>   {
>> -	sclp_read_scp_info((void *)_read_info, SCCB_SIZE);
> 	sclp_read_scp_info((void *)_read_info,
> 		test_facility(140) ? sizeof(_read_info) : SCCB_SIZE;
>
>> +	sclp_read_scp_info((void *)_read_info);
>>   	read_info = (ReadInfo *)_read_info;
>>   }
>>   

You are right, no need to begin with a short buffer if we can go with a 
big one at first try.

I take it

thx