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Date:   Tue, 26 May 2020 14:33:00 +0200
From:   Greg KH <gregkh@linuxfoundation.org>
To:     Alexander Graf <graf@amazon.de>
Cc:     Andra Paraschiv <andraprs@amazon.com>,
        linux-kernel@vger.kernel.org,
        Anthony Liguori <aliguori@amazon.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Colm MacCarthaigh <colmmacc@amazon.com>,
        Bjoern Doebel <doebel@amazon.de>,
        David Woodhouse <dwmw@amazon.co.uk>,
        Frank van der Linden <fllinden@amazon.com>,
        Martin Pohlack <mpohlack@amazon.de>,
        Matt Wilson <msw@amazon.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Balbir Singh <sblbir@amazon.com>,
        Stefano Garzarella <sgarzare@redhat.com>,
        Stefan Hajnoczi <stefanha@redhat.com>,
        Stewart Smith <trawets@amazon.com>,
        Uwe Dannowski <uwed@amazon.de>, kvm@vger.kernel.org,
        ne-devel-upstream@amazon.com
Subject: Re: [PATCH v3 07/18] nitro_enclaves: Init misc device providing the
 ioctl interface
Message-ID: <20200526123300.GA2798@kroah.com>
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On Tue, May 26, 2020 at 01:42:41PM +0200, Alexander Graf wrote:
> 
> 
> On 26.05.20 08:51, Greg KH wrote:
> > 
> > On Tue, May 26, 2020 at 01:13:23AM +0300, Andra Paraschiv wrote:
> > > +#define NE "nitro_enclaves: "
> > 
> > Again, no need for this.
> > 
> > > +#define NE_DEV_NAME "nitro_enclaves"
> > 
> > KBUILD_MODNAME?
> > 
> > > +#define NE_IMAGE_LOAD_OFFSET (8 * 1024UL * 1024UL)
> > > +
> > > +static char *ne_cpus;
> > > +module_param(ne_cpus, charp, 0644);
> > > +MODULE_PARM_DESC(ne_cpus, "<cpu-list> - CPU pool used for Nitro Enclaves");
> > 
> > Again, please do not do this.
> 
> I actually asked her to put this one in specifically.
> 
> The concept of this parameter is very similar to isolcpus= and maxcpus= in
> that it takes CPUs away from Linux and instead donates them to the
> underlying hypervisor, so that it can spawn enclaves using them.
> 
> From an admin's point of view, this is a setting I would like to keep
> persisted across reboots. How would this work with sysfs?

How about just as the "initial" ioctl command to set things up?  Don't
grab any cpu pools until asked to.  Otherwise, what happens when you
load this module on a system that can't support it?

module parameters are a major pain, you know this :)

> So yes, let's give everyone in CC the change to review v3 properly first
> before v4 goes out.
> 
> > And get them to sign off on it too, showing they agree with the design
> > decisions here :)
> 
> I would expect a Reviewed-by tag as a result from the above would satisfy
> this? :)

That would be most appreciated.

thanks,

greg k-h