linux-kernel - Re: [RFC PATCH 10/10] vfio/type1: Register device notifier

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Message-ID: <20210226054706.GB2764758@infradead.org>
Date:   Fri, 26 Feb 2021 05:47:06 +0000
From:   Christoph Hellwig <hch@...radead.org>
To:     Jason Gunthorpe <jgg@...dia.com>
Cc:     Alex Williamson <alex.williamson@...hat.com>, cohuck@...hat.com,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        peterx@...hat.com
Subject: Re: [RFC PATCH 10/10] vfio/type1: Register device notifier

On Mon, Feb 22, 2021 at 01:55:23PM -0400, Jason Gunthorpe wrote:
> > +static bool strict_mmio_maps = true;
> > +module_param_named(strict_mmio_maps, strict_mmio_maps, bool, 0644);
> > +MODULE_PARM_DESC(strict_mmio_maps,
> > +		 "Restrict to safe DMA mappings of device memory (true).");
> 
> I think this should be a kconfig, historically we've required kconfig
> to opt-in to unsafe things that could violate kernel security. Someone
> building a secure boot trusted kernel system should not have an
> options for userspace to just turn off protections.

Agreed, but I'd go one step further:  Why should we allow the unsafe
mode at all?