Messages in this thread | | | Date | Fri, 17 May 2013 10:45:36 +0900 | From | HATAYAMA Daisuke <> | Subject | Re: [PATCH v6 0/8] kdump, vmcore: support mmap() on /proc/vmcore |
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(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
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