From: David Vrabel Date: Fri, 10 Jan 2014 16:46:33 +0000 (+0100) Subject: x86: map portion of kexec crash area that is within the direct map area X-Git-Tag: archive/raspbian/4.8.0-1+rpi1~1^2~5676 X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=0896bd8bea84526b00e00d2d076f4f953a3d73cb;p=xen.git x86: map portion of kexec crash area that is within the direct map area Commit 7113a45451a9f656deeff070e47672043ed83664 (kexec/x86: do not map crash kernel area) causes fatal page faults when loading a crash image. The attempt to zero the first control page allocated from the crash region will fault as the VA return by map_domain_page() has no mapping. The fault will occur on non-debug builds of Xen when the crash area is below 5 TiB (which will be most systems). The assumption that the crash area mapping was not used is incorrect. map_domain_page() is used when loading an image and building the image's page tables to temporarily map the crash area, thus the mapping is required if the crash area is in the direct map area. Reintroduce the mapping, but only the portions of the crash area that are within the direct map area. Reported-by: Don Slutz Signed-off-by: David Vrabel Tested-by: Don Slutz Reviewed-by: Daniel Kiper Tested-by: Daniel Kiper This is really just a band aid - kexec shouldn't rely on the crash area being always mapped when in the direct mapping range (and it didn't use to in its previous form). That's primarily because map_domain_page() (needed when the area is outside the direct mapping range) may be unusable when wanting to kexec due to a crash, but also because in the case of PFN compression the kexec range (if specified on the command line) could fall into a hole between used memory ranges (while we're currently only ignoring memory at the top of the physical address space, it's pretty clear that sooner or later we will want that selection to become more sophisticated in order to maximize the memory made use of). Acked-by: Jan Beulich --- diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c index 4833ca33bd..b49256d5ad 100644 --- a/xen/arch/x86/setup.c +++ b/xen/arch/x86/setup.c @@ -1098,6 +1098,17 @@ void __init __start_xen(unsigned long mbi_p) PFN_UP(mod[i].mod_end), PAGE_HYPERVISOR); } + if ( kexec_crash_area.size ) + { + unsigned long s = PFN_DOWN(kexec_crash_area.start); + unsigned long e = min(s + PFN_UP(kexec_crash_area.size), + PFN_UP(__pa(HYPERVISOR_VIRT_END - 1))); + + if ( e > s ) + map_pages_to_xen((unsigned long)__va(kexec_crash_area.start), + s, e - s, PAGE_HYPERVISOR); + } + xen_virt_end = ((unsigned long)_end + (1UL << L2_PAGETABLE_SHIFT) - 1) & ~((1UL << L2_PAGETABLE_SHIFT) - 1); destroy_xen_mappings(xen_virt_end, XEN_VIRT_START + BOOTSTRAP_MAP_BASE);