On Thu, Mar 10, 2016 at 1:56 AM, Ingo Molnar <mingo@xxxxxxxxxx> wrote: > > * Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote: > >> On Fri, Feb 12, 2016 at 11:04 AM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote: >> > On Mon, Sep 21, 2015 at 11:23 PM, Ingo Molnar <mingo@xxxxxxxxxx> wrote: >> >> So when memory hotplug removes a piece of physical memory from pagetable >> >> mappings, it also frees the underlying PGD entry. >> >> >> >> This complicates PGD management, so don't do this. We can keep the >> >> PGD mapped and the PUD table all clear - it's only a single 4K page >> >> per 512 GB of memory hotplugged. >> > >> > Ressurecting an ancient thread: I want this particular change to make >> > it (much) easier to make vmapped stacks work correctly. Could it be >> > applied by itself? >> > >> >> It's incomplete. pageattr.c has another instance of the same thing. >> I'll see if I can make it work, but I may end up doing something a >> little different. > > If so then mind picking up (and fixing ;-) tip:WIP.x86/mm in its entirety? It's > well tested so shouldn't have too many easy to hit bugs. Feel free to rebase and > restructure it, it's a WIP tree. I'll chew on this one patch a bit and see where the whole things go. If I can rebase the rest on top, I'll use them. BTW, how are current kernels possibly correct when this code runs? We zap a pgd from the init pgd. I can't find any code that would try to propagate that zapped pgd to other pgds. Then, if we hotplug in some more memory or claim the slot for vmap, we'll install a new pgd entry, and we might access *that* through a different pgd. There vmalloc fault fixup won't help because the MMU will chase a stale pointer in the old pgd. So we might actually need this patch sooner rather than later. > > I keep getting distracted with other things but I'd hate if this got dropped on > the floor. > > Thanks, > > Ingo -- Andy Lutomirski AMA Capital Management, LLC -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>