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Subject: Re: [PATCH 4/6] s390: add system call to run tasks with modified
 branch prediction
To: Florian Weimer <fweimer@redhat.com>,
        Martin Schwidefsky <schwidefsky@de.ibm.com>,
        linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org,
        kvm@vger.kernel.org
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Cornelia Huck <cohuck@redhat.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jon Masters <jcm@redhat.com>,
        Marcus Meissner <meissner@suse.de>,
        Jiri Kosina <jkosina@suse.cz>
References: <1516182519-10623-1-git-send-email-schwidefsky@de.ibm.com>
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 <5bda76be-0fec-8165-20bf-5cd8e51e955a@redhat.com>
From: Christian Borntraeger <borntraeger@de.ibm.com>
Date: Wed, 17 Jan 2018 12:14:52 +0100
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On 01/17/2018 11:03 AM, Florian Weimer wrote:
> On 01/17/2018 10:48 AM, Martin Schwidefsky wrote:
>>          rc = syscall(__NR_s390_modify_bp);
>>          if (rc) {
>>                  perror("s390_modify_bp");
>>                  exit(EXIT_FAILURE);
>>          }
> 
> Isn't this traditionally done through personality or prctl?

I think we want this per thread (and not per process). So I assume personality
will not work out. Can a prctl be done per thread?

> 
> This looks like something other architectures may want as well.

Probably.