To prevent speculative intruction fetches from MMIO ranges that may have side effects on reads, the architecture requires device mappings to be created with the XN or UXN/PXN bits set (for the ARM/EL2 and EL1&0 translation regimes, respectively.) Note that, in the ARM case, this involves moving all accesses to a client domain since permission attributes like XN are ignored from a manager domain. The use of a client domain is actually mandated explicitly by the UEFI spec. Reported-by: Heyi Guo <heyi.guo@linaro.org> Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org> git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18891 6f19259b-4bc3-4df7-8a09-765794883524