On Thu, 2014-01-09 at 16:27 -0500, Vivek Goyal wrote: > On Thu, Jan 09, 2014 at 11:34:30AM -0700, Toshi Kani wrote: > > On Thu, 2014-01-09 at 13:23 -0500, Vivek Goyal wrote: > > > On Thu, Jan 09, 2014 at 10:24:25AM -0700, Toshi Kani wrote: > > > > > > [..] > > > > > I think creating a new command line option is simpler as compared to > > > > > creating a new flag in bootparam which in turn disables memory > > > > > hotplug. > > > > > More users can use that option. For example, if for some reason > > > > > hotplug > > > > > code is crashing, one can just disable it on command line as work > > > > > around > > > > > and move on. > > > > > > > > I do not have a strong opinion about having such option. However, I > > > > think it is more user friendly to keep the exactmap option works alone > > > > on any platforms. > > > > > > I think we should create internally a variable which will disable memory > > > hotplug. And set that variable based on memmap=exactmap, mem=X and also > > > provide a way to disable memory hotplug directly using command line > > > option. > > > > > > Current kexec-tools can use memmap=exactmap and be happy. I am writing > > > a new kexec syscall and will not be using memmap=exactmap and would need > > > to use that command line option to disable memory hotplug behavior. > > > > Sounds good to me. > > Nobody responded to my other question, so I would ask it again. > > Assume we have disabled hotplug memory in second kernel. First kernel > saw hotplug memory and assume crash kernel reserved region came from > there. We will pass this memory in bootparams to second kernel and it > will show up in E820 map. It should still be accessible in second kernel, > is that right?
Yes. > Or there is some dependency on ACPI doing some magic before this memory > range is available in second kernel? No. The 1st kernel reserves the crash kernel region, which cannot be hot-deleted. So, this region continues to be accessible by the 2nd kernel without any operation. I am more curious to know how makedumpfile decides what memory ranges to dump. The 1st kernel may have performed memory hot-add / delete operations before a crash, so it needs to know the valid physical address range at the time of crash, and may not rely on the E820 map from BIOS (which is stale). Am I right to assume that makedumpfile gets it from the page tables of the 1st kernel? Thanks, -Toshi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
