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From: Thomas Huth <thuth@redhat.com>
Message-ID: <ae4dba44-c634-062c-d412-201d1f10be32@redhat.com>
Date: Mon, 27 Feb 2017 08:30:16 +0100
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Subject: Re: [Qemu-devel] [PATCH v3] target-s390x: Implement stfl and stfle
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To: Michal Marek <mmarek@suse.com>, Richard Henderson <rth@twiddle.net>, Alexander Graf <agraf@suse.de>
Cc: Eric Bischoff <ebischoff@suse.com>, Miroslav Benes <mbenes@suse.cz>, qemu-devel@nongnu.org, David Hildenbrand <david@redhat.com>

On 26.02.2017 19:57, Michal Marek wrote:
> Dne 26.2.2017 v 12:22 Thomas Huth napsal(a):
>> On 26.02.2017 00:38, Michal Marek wrote:
>>> The implementation is partially cargo cult based, but it works for the
>>> linux kernel use case.
>>>
>>> Signed-off-by: Michal Marek <mmarek@suse.com>
>>> ---
>>> v3:
>>>  - Initialize the buffer in do_stfle()
>>> v2:
>>>  - STFLE is not a privileged instruction, go through the MMU to store the
>>>    result
>>>  - annotate the stfl helper with TCG_CALL_NO_RWG
>>>  - Use a large enough buffer to hold the feature bitmap
>>>  - Fix coding style of the stfle helper
>>> ---
>>>  target/s390x/cpu_features.c |  6 ++++--
>>>  target/s390x/cpu_features.h |  2 +-
>>>  target/s390x/helper.h       |  2 ++
>>>  target/s390x/insn-data.def  |  2 ++
>>>  target/s390x/misc_helper.c  | 36 ++++++++++++++++++++++++++++++++++++
>>>  target/s390x/translate.c    | 17 +++++++++--------
>>>  6 files changed, 54 insertions(+), 11 deletions(-)
[...]
>>> +uint64_t HELPER(stfle)(CPUS390XState *env, uint64_t a0, uint64_t r0)
>>> +{
>>> +    int need, len = r0 & 0xff;
>>
>> According to the POP spec, the address "must be designated on a
>> doubleword boundary; otherwise, a specification exception is recognized."
>> Could you please add this check here (or in translate.c)?
> 
> Dumb question, but how do I signal a specification exception?
> s390_cpu_do_interrupt() does not seem to be prepared for it.

Not sure, but I think something like

 program_interrupt(env, PGM_SPECIFICATION, 4);

should do the job here.

 Thomas