Re: [kvm-unit-tests PATCH v2] s390x: Interception tests

[Thomas Huth <thuth@redhat.com>]

On 02.06.2017 18:22, David Hildenbrand wrote:
> 
>>>> +static uint8_t pagebuf[PAGE_SIZE * 2] __attribute__((aligned(PAGE_SIZE)));
>>>> +
>>>> +/* Enable or disable low-address protection */
>>>> +static void set_low_prot(bool enable)
>>>> +{
>>>> +	uint64_t cr0;
>>>> +
>>>> +	asm volatile (" stctg 0,0,%0 " : : "Q"(cr0));
>>>
>>> Use %c0 instead?
>>
>> It's got to be %%c0 ... not sure whether this looks really nicer here?
> 
> %c0 should work, e.g. do a "git grep "%c0" in linux.git
> 
> arch/s390/kernel/base.S:        lctlg   %c0,%c0,0(%r4)

Well, that's a .S file ... for inline assembly in .c files, you need two
percentage characters.

>>>> +/* Test the TEST BLOCK instruction */
>>>> +static void test_testblock(void)
>>>> +{
>>>> +	int cc;
>>>> +
>>>> +	memset(pagebuf, 0xaa, PAGE_SIZE);
>>>> +
>>>> +	asm volatile (
>>>> +		" lghi	0,0\n"
>>>
>>> %0,0 ?
>>
>> That's certainly wrong, since %0 is the reference to the first output
>> parameter (cc). You likely mean %%0 or %%r0 ... and that looks rather
>> cumbersome, too. I think I prefer the plain "0" here, what do you think?
> 
> Sorry, of course I meant %r0. My keyboard ate one character ;)
> 
> (again, only one % is required, see e.g. arch/s390/kernel/entry.S)

Dito, also %% required here, since we're not in a .S file.

 Thomas