On Wed, Jul 11, 2012 at 12:04 PM, Arun KS <getarunks@xxxxxxxxx> wrote: > Hello Mulyadi, > > On Tue, Jul 10, 2012 at 9:42 PM, Mulyadi Santosa > <mulyadi.santosa@xxxxxxxxx> wrote: >> Hi.. >> >> On Tue, Jul 10, 2012 at 6:51 PM, Arun KS <getarunks@xxxxxxxxx> wrote: >>> Hello Experts, >>> >>> I have a requirement to change __log_buf memory(kernel printk buffer) >>> as non cacheable memory. >>> How can I change the page attributes for changing cache policy to non cacheable? >> >> I just can give short clue. I think somehow you must find its PTE >> entry...there, IIRC there is page attribute that can be changed to >> make it uncacheable. >> >> cross check the Intel processor manual for further clarification (if >> it's indeed x86 arch) > > __log_buf size is 512KB and PTE is mapped to a 1MB section. So if I > change the attribute for this 1MB section, lot of other stuffs(in this > 1MB bss section) will also become non-cachable. Looks like it is not > possible unless my __log_buf is 1MB in size. > Or I need to create another section like .init, .data, .bss and create > 4KB pages(with two levels of Page Tables) instead of 1M section. > > My arch is arm-v7 I went ahead and made my __log_buf size to 1MB. But the memory is not aligned to 1MB boundary. Here is what system.map shows. c08ac400 b __warned.32427 c08ac404 b __log_buf c09ac404 B console_set_on_cmdline c09ac408 b idle_notifier c09ac40c B sys_tz so __log_buf resides in two 1M sections in parts and it needs two PTEs. Then I added __aligned__(1024*1024) attribute to __log_buf array. This time compiler error "Error: alignment too large: 15 assumed" But __aligned_(32*1024) is working fine as below c08b84c0 b __warned.32427 c08c0000 b __log_buf c09c0000 B console_set_on_cmdline c09c8000 b idle_notifier c09c8004 B sys_tz Is it not possible to align more than 32KB? Any pointers? Thanks, Arun > > Thanks, > Arun >> >> -- >> 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
