On 07/07/2020 17.09, Janosch Frank wrote:
> On 7/7/20 1:45 PM, David Hildenbrand wrote:
>> On 07.07.20 13:44, Cornelia Huck wrote:
>>> On Tue, 7 Jul 2020 12:42:05 +0200
>>> Thomas Huth <thuth@xxxxxxxxxx> wrote:
>>>
>>>> When running the kvm-unit-tests with TCG on s390x, the cpumodel test
>>>> always reports the error about the missing DFP (decimal floating point)
>>>> facility. This is kind of expected, since DFP is not required for
>>>> running Linux and thus nobody is really interested in implementing
>>>> this facility in TCG. Thus let's mark this as an expected error instead,
>>>> so that we can run the kvm-unit-tests also with TCG without getting
>>>> test failures that we do not care about.
>>>>
>>>> Signed-off-by: Thomas Huth <thuth@xxxxxxxxxx>
>>>> ---
>>>> v2:
>>>> - Rewrote the logic, introduced expected_tcg_fail flag
>>>> - Use manufacturer string instead of VM name to detect TCG
>>>>
>>>> s390x/cpumodel.c | 49 ++++++++++++++++++++++++++++++++++++++++++------
>>>> 1 file changed, 43 insertions(+), 6 deletions(-)
>>>
>>> (...)
>>>
>>>> +static bool is_tcg(void)
>>>> +{
>>>> + const char qemu_ebcdic[] = { 0xd8, 0xc5, 0xd4, 0xe4 };
>>>> + bool ret = false;
>>>> + uint8_t *buf;
>>>> +
>>>> + buf = alloc_page();
>>>> + if (!buf)
>>>> + return false;
>>>> +
>>>> + if (stsi(buf, 1, 1, 1)) {
>>>> + goto out;
>>>> + }
>>>
>>> This does an alloc_page() and a stsi() every time you call it...
>>>
>>>> +
>>>> + /*
>>>> + * If the manufacturer string is "QEMU" in EBCDIC, then we are on TCG
>>>> + * (otherwise the string is "IBM" in EBCDIC)
>>>> + */
>>>> + if (!memcmp(&buf[32], qemu_ebcdic, sizeof(qemu_ebcdic)))
>>>> + ret = true;
>>>> +out:
>>>> + free_page(buf);
>>>> + return ret;
>>>> +}
>>>> +
>>>> +
>>>> int main(void)
>>>> {
>>>> int i;
>>>> @@ -46,11 +81,13 @@ int main(void)
>>>>
>>>> report_prefix_push("dependency");
>>>
>>> ...so maybe cache the value for is_tcg() here instead of checking
>>> multiple times in the loop?
>>
>> Maybe move it to common code and do the detection early during boot? The
>> n provide is_tcg() or sth. like that. Could be helpful in other context
>> maybe.
>>
>
> Well we also already have a check for zvm 6 with stsi 3.2.2 in skey.c
> I'm not completely convinced that I want to loose two pages and a few
> cycles on every startup for two separate test cases.
It certainly does not make sense to run the stsi calls during each and
every startup ... but I can move the is_tcg() function to the library
and make it a little bit smarter. I'll prepare a v3...
Thomas
