Vivek Goyal <vgoyal at redhat.com> writes: > Hi Bob, > > I am CCing this thread to kexec mailing list. It is good to discuss > the issue there to get the ideas. > > I will summarize the discussion so far. > > Bob is running into MCA in second kernel in kdump. Reason seems to be > that second kernel is trying to access the memory area marked as > GART aperture (by first kernel). Because GART aperture does not appear > as "reserved" or something else in /proc/iomem (in case kernel has > overridden the BIOS settings and has reserved a memory area), second > kernel thinks it is a valid RAM area and tries to dump it and runs into > issues. > > Few options Bob is considering are. > > - Update "e820" memory map to mark GART aperture as reserved, which will > be reflected in /proc/iomem also. Kexec-tools will not pass reserved > area to second kernel and it will not try to dump this area. > > > - Mark GART aperture as "GART aperture" in /proc/iomem and modify > kexec-tools to filter out this memroy from memory map passed to second > kernel. We should definitely reserve the resource, and it should definitely show up in /proc/iomem. > - Disable cpu side GART access in first kernel so that even if second > kernel tries to access it, it does not run into isseus. This is an interesting one. When I looked at this years ago I had the feeling that if we did this we could actually always use a 2G Aperture at a fixed address, and require going through the gart for all of lowmem. But that is a little more than we are talking about. Eric
