> So, in the start, the page might have kernel mode address, but in the > end it has user mode address. But kernel is still the one that tracks > all the page...be it anonymous or non anonymous ones. Not really. In this particular case of .nopage (page fault handler) of vma, we already have a user space virtual address for the faulty page, we just need it to map it with a physical page frame (RAM or device memory). Just allocate a physical page frame without any address, caller for .nopage will take care of properly setting its user space virtual address (page->va). So, no association with kernel space virtual address is required, e.g. it can be high memory page too without any kernel mapping. Rajat On Sat, Feb 19, 2011 at 2:10 PM, Mulyadi Santosa <mulyadi.santosa@xxxxxxxxx> wrote: > Hi :) > > I'll try to help... > > On Sat, Feb 19, 2011 at 13:10, anish singh <anish198519851985@xxxxxxxxx> wrote: >> As i understood whenver a user space program is run it is represented in >> kernel using VMA which is managed by struct mm_struct >> and whenever the program is trying to read/write to a memory location in >> user space it will be directed to physical address using PAGE TABLE >> translation done by struct mm_struct(done in kernel space).Am i right? > > i think not "done" but mm_struct points to PGD that represent's the > whole process address space. Using information provided there, MMU > does translation. > >> Suppose a simple driver wants the user to directly access its device memory >> then we use mmap.This mmap associates a set of user space virtual address >> with device driver memory and it is done by creating kernel page tables for >> the user space virtual addresses.Is the page table translation done >> everytime whenever user space does read/write to the device memory?? > > if it's recently translated, quite likely it is already cached in TLB > (translation look aside buffer) > >> In .nopage function call we return the page associated with the physical >> address which the user wants to associate with user space virtual address.Is >> the page address returned by the nopage function same as seen by the user or >> will it be converted to user space virtual address(range between 0-2 GB)? > > AFAIK, nopage is one of the functions that handle minor page fault, no? > > Anyway, memory allocation, usually start by kernel allocates a page. > Then it is "handed" to user space memory allocator. > > So, in the start, the page might have kernel mode address, but in the > end it has user mode address. But kernel is still the one that tracks > all the page...be it anonymous or non anonymous ones. > > Does it help? :) > > > > -- > regards, > > Mulyadi Santosa > Freelance Linux trainer and consultant > > blog: the-hydra.blogspot.com > training: mulyaditraining.blogspot.com > > _______________________________________________ > Kernelnewbies mailing list > Kernelnewbies@xxxxxxxxxxxxxxxxx > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
