Messages in this thread | | | From | Pavel Tatashin <> | Date | Sat, 13 Feb 2021 13:17:11 -0500 | Subject | Re: [PATCH] arm64: mm: correct the start of physical address in linear map |
| |
> We're ignoring the portion from the linear mapping's start PA to the > point of wraparound. Could the start and end of the hot plugged memory > fall within this range and, as a result, the hot plug operation be > incorrectly blocked?
Hi Tyler,
Thank you for looking at this fix. The maximum addressable PA's can be seen in this function: id_aa64mmfr0_parange_to_phys_shift(). For example for PA shift 32, the linear map must be able to cover any physical addresses from 0 to "1 << 32". Therefore, 0 to __pa(PAGE_END - 1); must include 0 to "1<<32".
The randomization of the linear map tries to hide where exactly within the linear map the [0 to max_phys] addresses are located by changing PHYS_OFFSET (linear map space is usually much bigger than PA space). Therefore, the beginning or end of a linear map can actually convert to completely bagus high PA addresses, but this is normal.
Thank you, Pasha
> > Tyler > > > + > > /* > > * Linear mapping region is the range [PAGE_OFFSET..(PAGE_END - 1)] > > * accommodating both its ends but excluding PAGE_END. Max physical > > * range which can be mapped inside this linear mapping range, must > > * also be derived from its end points. > > */ > > - return start >= __pa(_PAGE_OFFSET(vabits_actual)) && > > - (start + size - 1) <= __pa(PAGE_END - 1); > > + return start >= start_linear_pa && (start + size - 1) <= end_linear_pa; > > } > > > > int arch_add_memory(int nid, u64 start, u64 size, > > -- > > 2.25.1 > >
| |