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Re: [Xen-devel] asterisk, ztdummy, and usb (and HZ = 100 under xen ???)

On 22 May 2005, at 08:56, James Harper wrote:

Assuming you have restricted the domain to just accessing registers
IRQs belonging to the device it controls, I think the only way would
by programming the device to wreak havoc on its behalf (by DMAing
arbitrary memory).

Is there a way to protect against rogue DMA writes (without knowing the
details of every particular piece of hardware) or is it just the price
to be paid for direct hardware access?

You need an IOMMU. Then the 'bus addresses' you program into the device are checked and translated by the IOMMU when it attempts to access memory.

Chipset extensions to support protection from rogue devices is likely to appear for commodity x86 systems in the next couple of years, I think.

 -- Keir

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