On Mon, Jul 28, 2008 at 09:31:10AM -0400, Vivek Goyal wrote: > On Mon, Jul 28, 2008 at 11:51:19AM +1000, Simon Horman wrote: > > [ Updated Vivek's email address to his vgoyal@xxxxxxxxxx in CC list > > Added Terry Loftin, Tony Luck, Erik Biedermann and linux-ia64 to CC list ] [snip] > > 1) Always parse the elfcorehdr kernel command line option > > and set elfcorehdr_addr accordingly - currently this is only > > done if CONFIG_PROC_VMCORE is set. > > > > This is nice as it won't need any modifications to kexec-tools > > nor any command line bloat. > > > > A minor difficulty is working out where to initialise elfcorehdr_addr. > > Sometimes in include/linux/crash_dump.h and sometimes in > > fs/proc/vmcore.c seems horrible to me. > > > > Another problem is that would be alive and well in > > code that really only uses it to check if kdump was activated or not > > - a minor naming issue. > > > > Hi Simon, > > There are some kernel bits (like iommu initialization patch), which need to > take special action if they are booting after a kexec on panic (Generally we > are referring it to booting into kdump kernel) and that's why the notion > is_kdump_kernel(). > > To me, is_kdump_kernel() symbolizes whether I am booting after kexec on > panic and not just the fact if CONFIG_CRASH_DUMP is enabled or not in this > kernel. > > So I would think that lets not rename it to kernel_has_vmcore(), instead > lets write few lines of comments before function is_kdump_kernel() to > clarify its meaning. > > Secondly, we are using elfcorehdr_addr to determine whether this kernel > is booting after a panic so elfcorehdr_addr is not just limited to > CONFIG_PROC_VMCORE now and we should probably pull it out of > fs/proc/vmcore.c. How about declaring and initializing this variable in > kernel/kexec.c under CONFIG_CRASH_DUMP and always parse elfcorehdr_addr > irrespective of the setting of CONFIG_PROC_VMCORE? Agreed. Like Eric I think that this is a reasonable solution given the current state of things. I'll reply to your patches after looking at them a bit more closely. > > 2) Add a new kernel command line option, perhaps in_kdump > > > > This is bloat to get around elfcorehdr_addr initialisation and > > naming awkwardness above. > > > > 3) Make select CONFIG_PROC_VMCORE when CONFIG_CRASH_DUMP is selected, > > or perhaps even just remove CONFIG_PROC_VMCORE and only use > > CONFIG_CRASH_DUMP instead. The effect would be the same either way. > > > > Pro: One less thing to be confused about > > > > Con: Bloat for people who want kdump without vmcore. > > I wonder what usage case that is. > > Argument was people can use /dev/oldmem and not use /proc/vmcore. So far > I don't know anybody who uses /dev/oldmem to capture dump and not > /proc/vmcore. What I was getting at is that frangly the three variables CONFIG_KEXEC, CONFIG_CRASH_DUMP and CONFIG_PROC_VMCORE seem to confuse people. I've seen them used incorrectly several times now. So if there is a way to simplyfy things, even slightly, I think that would be a good idea. But if there isn't, so be it. -- Horms -- To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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