tree 7de693ac6a137dfab2f07a606874f58cf3618fb1
parent 0c7ffc977195c1f71c8132eb5616827e589d4a0f
author Max Erenberg <merenber@uwaterloo.ca> 1703547872 -0500
committer Michael Tokarev <mjt@tls.msk.ru> 1704482934 +0300

edu: fix DMA range upper bound check

The edu_check_range function checks that start <= end1 < end2, where
end1 is the upper bound (exclusive) of the guest-supplied DMA range and
end2 is the upper bound (exclusive) of the device's allowed DMA range.
When the guest tries to transfer exactly DMA_SIZE (4096) bytes, end1
will be equal to end2, so the check fails and QEMU aborts with this
puzzling error message (newlines added for formatting):

  qemu: hardware error: EDU: DMA range
    0x0000000000040000-0x0000000000040fff out of bounds
   (0x0000000000040000-0x0000000000040fff)!

By checking end1 <= end2 instead, guests will be allowed to transfer
exactly 4096 bytes. It is not necessary to explicitly check for
start <= end1 because the previous two checks (within(addr, start, end2)
and end1 > addr) imply start < end1.

Fixes: b30934cb52a7 ("hw: misc, add educational driver", 2015-01-21)
Signed-off-by: Max Erenberg <merenber@uwaterloo.ca>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>