linux-kernel - Re: [PATCH 4/6] s390: add system call to run tasks with modified branch prediction

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Message-Id: <c80554d9-a7e0-00cf-9f03-b16ce34205c5@de.ibm.com>
Date:   Wed, 17 Jan 2018 12:14:52 +0100
From:   Christian Borntraeger <borntraeger@...ibm.com>
To:     Florian Weimer <fweimer@...hat.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     Heiko Carstens <heiko.carstens@...ibm.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jon Masters <jcm@...hat.com>,
        Marcus Meissner <meissner@...e.de>,
        Jiri Kosina <jkosina@...e.cz>
Subject: Re: [PATCH 4/6] s390: add system call to run tasks with modified
 branch prediction



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.