Re: [Qemu-devel] [PATCH v3 29/29] tests/tcg: target/s390x: Test MVO

[David Hildenbrand <david@redhat.com>]

On 18.09.19 13:24, Alex Bennée wrote:
> 
> David Hildenbrand <david@redhat.com> writes:
> 
>> On 18.09.19 11:47, Alex Bennée wrote:
>>>
>>> David Hildenbrand <david@redhat.com> writes:
>>>
>>>> Let's add the simple test based on the example from the PoP.
>>>>
>>>> Signed-off-by: David Hildenbrand <david@redhat.com>
>>>> ---
>>>>  tests/tcg/s390x/Makefile.target |  1 +
>>>>  tests/tcg/s390x/mvo.c           | 25 +++++++++++++++++++++++++
>>>>  2 files changed, 26 insertions(+)
>>>>  create mode 100644 tests/tcg/s390x/mvo.c
>>>>
>>>> diff --git a/tests/tcg/s390x/Makefile.target b/tests/tcg/s390x/Makefile.target
>>>> index 151dc075aa..6a3bfa8b29 100644
>>>> --- a/tests/tcg/s390x/Makefile.target
>>>> +++ b/tests/tcg/s390x/Makefile.target
>>>> @@ -6,3 +6,4 @@ TESTS+=ipm
>>>>  TESTS+=exrl-trt
>>>>  TESTS+=exrl-trtr
>>>>  TESTS+=pack
>>>> +TESTS+=mvo
>>>> diff --git a/tests/tcg/s390x/mvo.c b/tests/tcg/s390x/mvo.c
>>>> new file mode 100644
>>>> index 0000000000..5546fe2a97
>>>> --- /dev/null
>>>> +++ b/tests/tcg/s390x/mvo.c
>>>> @@ -0,0 +1,25 @@
>>>> +#include <stdint.h>
>>>> +#include <stdio.h>
>>>> +
>>>> +int main(void)
>>>> +{
>>>> +    uint8_t dest[6] = {0xff, 0x77, 0x88, 0x99, 0x0c, 0xff};
>>>> +    uint8_t src[5] = {0xee, 0x12, 0x34, 0x56, 0xee};
>>>> +    uint8_t expected[6] = {0xff, 0x01, 0x23, 0x45, 0x6c, 0xff};
>>>> +    int i;
>>>> +
>>>> +    asm volatile (
>>>> +        "    mvo 0(4,%[dest]),0(3,%[src])\n"
>>>> +        :
>>>> +        : [dest] "d" (dest + 1),
>>>> +          [src] "d" (src + 1)
>>>> +        : "memory");
>>>> +
>>>> +    for (i = 0; i < sizeof(expected); i++) {
>>>> +        if (dest[i] != expected[i]) {
>>>> +            fprintf(stderr, "bad data\n");
>>>> +            return 1;
>>>> +        }
>>>> +    }
>>>> +    return 0;
>>>> +}
>>>
>>> Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
>>>
>>> but...
>>>
>>> can this test be expanded to check the page cross cases that caused you
>>> so much trouble to track down?
>>
>> I might add a MVC test that tries to reproduce this. But with
>> speculative page faults and things like that it might not be very easy
>> to reproduce. However, I can give it a try.
> 
> I may not be fully understanding the correct behaviour but wouldn't the
> test be:
> 
>   * map two page's worth of address space
>   * mprot(!write) the top page
>   * attempt mvc based copy to mmap region (say p0+(PAGE_SIZE>>1) to p1+(PAGE_SIZE>>1))
>   * catch the fault
>   * check the bottom page wasn't written to

No, you are absolutely right, with memmap/mprot hackery + signal handler
this can be tested just fine. I'll craft something for the MVC instruction!

Thanks!

-- 

Thanks,

David / dhildenb