tree fa6c81a40a36d2c0da1cf20c5deb45cb9bd7ba95
parent f0fe510864a4520a85dfa35ae14f5f376c56efc7
author Avi Kivity <avi@qumranet.com> 1174387610 +0200
committer Avi Kivity <avi@qumranet.com> 1178178745 +0300

KVM: Avoid guest virtual addresses in string pio userspace interface

The current string pio interface communicates using guest virtual addresses,
relying on userspace to translate addresses and to check permissions.  This
interface cannot fully support guest smp, as the check needs to take into
account two pages at one in case an unaligned string transfer straddles a
page boundary.

Change the interface not to communicate guest addresses at all; instead use
a buffer page (mmaped by userspace) and do transfers there.  The kernel
manages the virtual to physical translation and can perform the checks
atomically by taking the appropriate locks.

Signed-off-by: Avi Kivity <avi@qumranet.com>