From: Vitaly Kuznetsov Date: Fri, 8 Aug 2014 21:22:05 +0000 (-0700) Subject: fs/proc/vmcore.c:mmap_vmcore: skip non-ram pages reported by hypervisors X-Git-Tag: omap-for-v3.17/fixes-against-rc2~116^2~115 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0692dedcf64bf3cdcfb9f6a51c70d49c8db351d2;p=pandora-kernel.git fs/proc/vmcore.c:mmap_vmcore: skip non-ram pages reported by hypervisors We have a special check in read_vmcore() handler to check if the page was reported as ram or not by the hypervisor (pfn_is_ram()). However, when vmcore is read with mmap() no such check is performed. That can lead to unpredictable results, e.g. when running Xen PVHVM guest memcpy() after mmap() on /proc/vmcore will hang processing HVMMEM_mmio_dm pages creating enormous load in both DomU and Dom0. Fix the issue by mapping each non-ram page to the zero page. Keep direct path with remap_oldmem_pfn_range() to avoid looping through all pages on bare metal. The issue can also be solved by overriding remap_oldmem_pfn_range() in xen-specific code, as remap_oldmem_pfn_range() was been designed for. That, however, would involve non-obvious xen code path for all x86 builds with CONFIG_XEN_PVHVM=y and would prevent all other hypervisor-specific code on x86 arch from doing the same override. [fengguang.wu@intel.com: remap_oldmem_pfn_checked() can be static] [akpm@linux-foundation.org: clean up layout] Signed-off-by: Vitaly Kuznetsov Reviewed-by: Andrew Jones Cc: Michael Holzheu Acked-by: Vivek Goyal Cc: David Vrabel Signed-off-by: Fengguang Wu Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Reading git-diff-tree failed