Architectures and Processors forum DBM bit in descriptor

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DBM bit in descriptor

digital_kevin over 6 years ago

Dear all:

As described in armv8 reference manual, DBM means " Dirty Bit Modifier".

My understanding is:

If DBM =1, it means that the page or block is dirty.

If DBM =0, it means the page or block is not dirty.

Is that rignt?

Top replies

Martin Weidmann over 6 years ago +1 suggested

Not exactly. When mapping in a "clean" write-able page the OS would set the attributes to AP="read-only" and DBM==1. On the first write, the hardware automatically updates AP from "read-only" to "read...
42Bastian Schick over 6 years ago in reply to digital_kevin +1 suggested

"When the hardware management of dirty state is enabled, if the Block or Page descriptor in a translation table indicates that a data access does not have write permission, then in situations where, without...