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.
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