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

On 22 May 2005, at 03:15, James Harper wrote:

Just on that subject, under what conditions would a domain with
permissions to access a pci device be able to bring down the machine if
I did something stupid in the kernel driver?

Assuming you have restricted the domain to just accessing registers and IRQs belonging to the device it controls, I think the only way would be by programming the device to wreak havoc on its behalf (by DMAing arbitrary memory). It also has control of an interrupt line, so if that is shared it might be possible for the domain to arrange an interrupt storm that either you mask, affecting servicing of other devices on that line, or you end up in interrupt livelock. This could be fixed by masking the interrupt, terminating the domain, clearing the enable bits in the device's PCI space, then unmasking the interrupt. In any case, legacy interrupts are on their way out, replaced with message-based interrupts.

 -- Keir

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