Quoting Linus Torvalds (2020-08-21 13:41:03) > On Fri, Aug 21, 2020 at 1:50 AM Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote: > > > > Since synchronising the PTE after assignment is a manual step, use the > > newly exported interface to flush the PTE after assigning via > > alloc_vm_area(). > > This commit message doesn't make much sense to me. > > Are you talking about synchronizing the page directory structure > across processes after possibly creating new kernel page tables? > > Because that has nothing to do with the PTE. It's all about making > sure the _upper_ layers of the page directories are populated > everywhere.. > > The name seems off to me too - what are you "flushing"? (And yes, I > know about the flush_cache_vmap(), but that looks just bogus, since > any non-mapped area shouldn't have any virtual caches to begin with, > so I suspect that is just the crazy architectures being confused - > flush_cache_vmap() is a no-op on any sane architecture - and powerpc > that mis-uses it for other things). I was trying to mimic map_kernel_range() which does the arch_sync_kernel_mappings and flush_cache_vmap on top of the apply_to_page_range performed by alloc_vm_area, because buried away in there, on x86-32, is a set_pmd(). Since map_kernel_range() wrapped map_kernel_range_noflush(), flush seemed like the right verb. Joerg pointed out that the sync belonged to __apply_to_page_range and fixed it in situ. -Chris
