Re: [kvm-unit-tests PATCH v2 3/3] s390x: Ultravisor guest API test

[Thomas Huth <thuth@redhat.com>]

On 30/07/2020 13.16, Cornelia Huck wrote:
> On Mon, 27 Jul 2020 05:54:15 -0400
> Janosch Frank <frankja@linux.ibm.com> wrote:
> 
>> Test the error conditions of guest 2 Ultravisor calls, namely:
>>      * Query Ultravisor information
>>      * Set shared access
>>      * Remove shared access
>>
>> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
>> Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
>> ---
>>  lib/s390x/asm/uv.h  |  68 +++++++++++++++++++
>>  s390x/Makefile      |   1 +
>>  s390x/unittests.cfg |   3 +
>>  s390x/uv-guest.c    | 159 ++++++++++++++++++++++++++++++++++++++++++++
>>  4 files changed, 231 insertions(+)
>>  create mode 100644 lib/s390x/asm/uv.h
>>  create mode 100644 s390x/uv-guest.c
>>
> 
> (...)
> 
>> +static inline int uv_call(unsigned long r1, unsigned long r2)
>> +{
>> +	int cc;
>> +
>> +	asm volatile(
>> +		"0:	.insn rrf,0xB9A40000,%[r1],%[r2],0,0\n"
>> +		"		brc	3,0b\n"
>> +		"		ipm	%[cc]\n"
>> +		"		srl	%[cc],28\n"
>> +		: [cc] "=d" (cc)
>> +		: [r1] "a" (r1), [r2] "a" (r2)
>> +		: "memory", "cc");
>> +	return cc;
>> +}
> 
> This returns the condition code, but no caller seems to check it
> (instead, they look at header.rc, which is presumably only set if the
> instruction executed successfully in some way?)
> 
> Looking at the kernel, it retries for cc > 1 (presumably busy
> conditions), and cc != 0 seems to be considered a failure. Do we want
> to look at the cc here as well?

It's there - but here it's in the assembly code, the "brc 3,0b".

Patch looks ok to me (but I didn't do a full review):

Acked-by: Thomas Huth <thuth@redhat.com>