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Date: Tue, 6 Oct 2015 15:15:57 +0300 From: Avi Kivity <avi@...lladb.com> To: Stephen Hemminger <stephen@...workplumber.org>, "Michael S. Tsirkin" <mst@...hat.com> Cc: dev@...k.org, hjk@...sjkoch.de, gregkh@...ux-foundation.org, linux-kernel@...r.kernel.org Subject: Re: [dpdk-dev] [PATCH 2/2] uio: new driver to support PCI MSI-X On 10/06/2015 10:33 AM, Stephen Hemminger wrote: > Other than implementation objections, so far the two main arguments > against this reduce to: > 1. If you allow UIO ioctl then it opens an API hook for all the crap out > of tree UIO drivers to do what they want. > 2. If you allow UIO MSI-X then you are expanding the usage of userspace > device access in an insecure manner. > > Another alternative which I explored was making a version of VFIO that > works without IOMMU. It solves #1 but actually increases the likely negative > response to arguent #2. This would keep same API, and avoid having to > modify UIO. But we would still have the same (if not more resistance) > from IOMMU developers who believe all systems have to be secure against > root. vfio's charter was explicitly aiming for modern setups with iommus. This could be revisited, but I agree it will have even more resistance, justified IMO. btw, (2) doesn't really add any insecurity. The user could already poke at the msix tables (as well as perform DMA); they just couldn't get a useful interrupt out of them. Maybe a module parameter "allow_insecure_dma" can be added to uio_pci_generic. Without the parameter, bus mastering and msix is disabled, with the parameter it is allowed. This requires the sysadmin to take a positive step in order to make use of their hardware. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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