linux-kernel - Re: [PATCH 2/5] vfio: introduce the VFIO_DMA_MAP_FLAG

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Message-ID: <CALCETrWzxjpKrou6J63_T75x=ZEGWCGbc4KEWT_AMvzSQNn1eg@mail.gmail.com>
Date:	Mon, 20 Oct 2014 14:37:17 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Antonios Motakis <a.motakis@...tualopensystems.com>
Cc:	kvmarm@...ts.cs.columbia.edu, iommu@...ts.linux-foundation.org,
	Alex Williamson <alex.williamson@...hat.com>,
	Will Deacon <will.deacon@....com>, tech@...tualopensystems.com,
	christoffer.dall@...aro.org, eric.auger@...aro.org,
	kim.phillips@...escale.com, marc.zyngier@....com,
	"open list:VFIO DRIVER" <kvm@...r.kernel.org>,
	"open list:ABI/API" <linux-api@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/5] vfio: introduce the VFIO_DMA_MAP_FLAG_NOEXEC flag

On Mon, Oct 13, 2014 at 6:09 AM, Antonios Motakis
<a.motakis@...tualopensystems.com> wrote:
> We introduce the VFIO_DMA_MAP_FLAG_NOEXEC flag to the VFIO dma map call,
> and expose its availability via the capability VFIO_DMA_NOEXEC_IOMMU.
> This way the user can control whether the XN flag will be set on the
> requested mappings. The IOMMU_NOEXEC flag needs to be available for all
> the IOMMUs of the container used.

Since you sent this to the linux-api list, I'll bite: what's the XN
flag?  I know what PROT_EXEC does when you mmap something, and I
presume that vfio is mmappable, but I don't actually have any clue
what this patch does.

I assume that this does not have anything to do with a non-CPU DMA
master executing code in main memory, because that makes rather little
sense.  (Or maybe it really does, in which case: weird.)

--Andy
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