From mboxrd@z Thu Jan  1 00:00:00 1970
From: Heiko Carstens <heiko.carstens@de.ibm.com>
Subject: Re: [PATCH 0/2] KVM: s390: avoid jump tables
Date: Thu, 8 Feb 2018 09:58:19 +0100
Message-ID: <20180208085819.GC3937@osiris>
References: <20180206112127.19014-1-borntraeger@de.ibm.com>
 <7e9bb181-cec9-0781-03c0-b74d5d087c8a@redhat.com>
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Cc: Christian Borntraeger <borntraeger@de.ibm.com>,
        Janosch Frank <frankja@linux.vnet.ibm.com>,
        KVM <kvm@vger.kernel.org>, Cornelia Huck <cohuck@redhat.com>,
        linux-s390 <linux-s390@vger.kernel.org>
To: David Hildenbrand <david@redhat.com>
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On Tue, Feb 06, 2018 at 01:30:28PM +0100, David Hildenbrand wrote:
> On 06.02.2018 12:21, Christian Borntraeger wrote:
> > Some old patches refreshed.
> > 
> 
> Certainly the right thing to do. Especially also interesting due to
> retpotline (if we get something like that on s390x). If I remember
> correctly, x86 highly benefits by replacing magic function pointer by
> switch statements.

If you look at the generated code for the first patch: gcc now generates
its own jump table which then jumps (indirectly) to a brasl... So it's two
instead of one branch.
I'm not saying that this patch is not good, but there seem be a wrong
assumptions about the benefit here.