Thursday, 27 February 2014

arm - How does TTBCR affect low addresses in ARMv8-A?


While reading about translation tables in ARMv8-A, I came across the following:



Depending on the size of the possible VA range, there can be even fewer levels. With a 4KB granule, for example, if the TTBCR is set so that low addresses span only 1GB, then levels 0 and 1 are not required and the translation starts at level 2, going down to level 3 for 4KB pages.



TTBCR selects if translation table walk is allowed and whether TTBR0 or TTBR1 is used. How does it affect the range of low addresses?




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