On 01/10/2018 05:42 AM, Laurent Vivier wrote: > Le 10/01/2018 à 09:43, David Hildenbrand a écrit : >> On 09.01.2018 00:10, Laurent Vivier wrote: >>> The MC68040 MMU provides the size of the access that >>> triggers the page fault. >>> >>> This size is set in the Special Status Word which >>> is written in the stack frame of the access fault >>> exception. >>> >>> So we need the size in m68k_cpu_unassigned_access() and >>> m68k_cpu_handle_mmu_fault(). >>> >>> To be able to do that, this patch modifies the prototype of >>> handle_mmu_fault handler, tlb_fill() and probe_write(). >>> do_unassigned_access() already includes a size parameter. >>> >>> This patch also updates handle_mmu_fault handlers and >>> tlb_fill() of all targets (only parameter, no code change). >>> >> >> There are a couple of places where you use "1" (when no other size is >> available). e.g. in get_page_addr_code(). >> >> Wonder if that's the right thing to do - are there any architectures >> that e.g. always fetch at least 2 bytes in these conditions? >> > > It's a good question. > > "1" is passed to probe_write() and tlb_fill() and handle_mmu_fault(). > probe_write() calls tlb_fill(), and tlb_fill() calls machine > handle_mmu_fault handler. > > As no existing handle_mmu_fault takes care of the access size, I think > passing 1 and ignoring it doesn't change the existing behavior. > > probe_write() is used to check if a page is writable, and none of the > callers is guessing the write can cross a page boundary, so 1 is the > good value in this case. > > get_page_addr_code() is the only user of tlb_fill() with 1. and callers > of get_page_addr_code() never guess the code address can run across a > page boundary. Some of them calls get_page_addr_code() a second time to > check this case. So I think using 1 is good solution, but perhaps the > code could be improved by adding the size parameter to get_page_addr_code(). > > My purpose was not to change the functions behavior, only to add the new > parameter. So using "1" when the size is not obvious is a good solution > to me.
I guess I don't really have a problem with "1". I do wonder if "0" might be a better value for "I don't know", because it is not mistakable with a real access of 1 byte. r~
