Messages in this thread | | | Date | Wed, 20 Dec 2017 20:50:11 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [patch V163 27/51] x86/mm/pti: Populate user PGD |
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On Wed, 20 Dec 2017, Juergen Gross wrote: > On 20/12/17 01:22, Thomas Gleixner wrote: > > On Tue, 19 Dec 2017, Thomas Gleixner wrote: > >> On Tue, 19 Dec 2017, Ingo Molnar wrote: > >> We don't run out of space, but the 0-day robot triggered a nasty issue. > >> > >> The fixmap bottom address, which contains the early_ioremap fixmap area, is: > >> > >> vaddr_bt = FIXADDR_TOP - FIX_BTMAP_BEGIN * PAGE_SIZE > >> > >> If that address is lower than: > >> > >> vaddr_end = __START_KERNEL_map + KERNEL_IMAGE_SIZE; > >> > >> then cleanup_highmap() will happily 0 out the PMD entry for the PTE page of > >> FIX_BTMAP. That entry was set up earlier in early_ioremap_init(). > >> > >> As a consequence the first call to __early_set_fixmap() which tries to > >> install a PTE for early_ioremap() will crash and burn. > >> > >> Below is a nasty hack which fixes the problem. Ideally we get all of this > >> cpu_entry_stuff out of the fixmap. I'll look into that later, but for now > >> the patch 'fixes' the issue. > > > > I had a stab on moving the cpu_entry_area to some other place. > > > > The patch below works, but: > > > > - it breaks i386 build because I have not yet found a way to place the > > CPU_ENTRY_AREA_BASE without creating include recursion hell > > > > - it probably does not work on XEN_PV, but I'm too tired now to figure > > that out. > > The attached patch lets the system come up as XEN_PV.
I folded it back to the proper place.
Thanks for looking!
tglx
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