Re: [RFC PATCH] virtio_ring: Use DMA API if guest memory is encrypted

On Wed, Apr 17, 2019 at 06:42:00PM -0300, Thiago Jung Bauermann wrote:

I rephrased it in terms of address translation. What do you think of
this version? The flag name is slightly different too:


VIRTIO_F_ACCESS_PLATFORM_NO_TRANSLATION This feature has the same
    meaning as VIRTIO_F_ACCESS_PLATFORM both when set and when not set,
    with the exception that address translation is guaranteed to be
    unnecessary when accessing memory addresses supplied to the device
    by the driver. Which is to say, the device will always use physical
    addresses matching addresses used by the driver (typically meaning
    physical addresses used by the CPU) and not translated further. This
    flag should be set by the guest if offered, but to allow for
    backward-compatibility device implementations allow for it to be
    left unset by the guest. It is an error to set both this flag and
    VIRTIO_F_ACCESS_PLATFORM.

OK so VIRTIO_F_ACCESS_PLATFORM is designed to allow unpriveledged
drivers. This is why devices fail when it's not negotiated.

This confuses me.
If driver is unpriveledged then what happens with this flag?
It can supply any address it wants. Will that corrupt kernel
memory?

-- 
MST