(2013/05/17 9:06), H. Peter Anvin wrote: > On 05/15/2013 02:05 AM, HATAYAMA Daisuke wrote: >> Currently, read to /proc/vmcore is done by read_oldmem() that uses >> ioremap/iounmap per a single page. For example, if memory is 1GB, >> ioremap/iounmap is called (1GB / 4KB)-times, that is, 262144 >> times. This causes big performance degradation. > > read_oldmem() is fundamentally broken and unsafe. It needs to be > unified with the plain /dev/mem code and any missing functionality fixed > instead of "let's just do a whole new driver". > > -hpa Do you mean range_is_allowed should be extended so that it checks according to memory map passed from the 1st kernel? BTW, read request to read_oldmem via read_vmcore and mmap on some part of the 1st kernel, seems safe since it's always restrected to within the memory map. Or is there other missing point? -- Thanks. HATAYAMA, Daisuke
