I'm having a problem where the method I am using for translation from virtual to physical address is not reliable. I am working on an application where multiple programs access a shared memory segmet allocated with shmget(), and a device must directly access the memory. I am using kiobuf_map_user() and virt_to_bus() to create a page table the hardware uses to convert a user logical address into a PCI bus address for the shared memory. Sometimes it comes up working fine, and seems to continue to work until the system is restarted. Other times after a restart, the virt_to_bus() returns 0x40000000 for every address. I've tried __pa() instead of virt_to_bus, but it had the same result. This is on an x86 type CPU, so virt_to_bus() is the same as virt_to_phys(). My driver module is like this: unsigned int user_virtual_address; // task virtual shared memory address struct kiobuf *iobuf; // structure containing map info long pci_address; // bus address for the hardware to use if (map_user_kiobuf(READ, iobuf, (unsigned long) user_virtual_address, 1) != 0) pci_address = virt_to_bus(page_address(iobuf->maplist[0])); I believe map_user_kiobuf() forces the pages in, but I also tried adding mem_map_reserve(virt_to_page(page_address(iobuf->maplist[0]))); before virt_to_bus() and had the same result. Can anyone tell me how I can reliably translate a user virtual address for host dram into a PCI bus address? Dave Z -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
