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From: David Hildenbrand <david@redhat.com>
Message-ID: <fea39dac-e9da-c466-a7a2-d55a726272b0@redhat.com>
Date: Thu, 2 Mar 2017 14:09:48 +0100
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Subject: Re: [Qemu-devel] [PATCH v4] target-s390x: Implement stfl and stfle
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To: Richard Henderson <rth@twiddle.net>, Thomas Huth <thuth@redhat.com>, Michal Marek <mmarek@suse.com>, Alexander Graf <agraf@suse.de>
Cc: Eric Bischoff <ebischoff@suse.com>, Miroslav Benes <mbenes@suse.cz>, qemu-devel@nongnu.org

>>> Of course, in practice we could reduce this to just one cpu_stl_data for
>>> STFL and one or two cpu_stq_data for STFLE.
>>
>> I think STFLE can store more than two 64-bit words, can't it?
> 
> Technically, yes.  But there are less than 128 bits defined.  Certainly much 
> less than the 4k bits that Michal prepares for.
> 

The architectural limit is 2k bytes (yes I said bytes).

Check out "struct kvm_s390_vm_cpu_machine - fac_list" /
KVM_S390_VM_CPU_MACHINE in
arch/s390/include/uapi/asm/kvm.h. Here we prepared for that.

Also note preparations for new stfl bits for future HW:

cd1836f583d7 (KVM: s390: instruction-execution-protection support)
-> bit 130
a679c547d19d (KVM: s390: gaccess: add ESOP2 handling)
-> bit 131

However, for now 128 bit should be more then enough, as TCG still misses
loads of features. CPU model still isn't properly wired up for TCG yet.

-- 
Thanks,

David