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authorJiri Bohac <jbohac@suse.cz>2018-01-06 04:00:13 +0300
committerThomas Gleixner <tglx@linutronix.de>2018-01-11 17:09:24 +0300
commit2a3e83c6f96c513f43ce5a8c9034608ea584a255 (patch)
tree16b19f7be5c0d4aba45652409632325504fad62b /arch/x86/xen
parentb2cd1df66037e7c4697c7e40496bf7e4a5e16a2d (diff)
downloadlinux-2a3e83c6f96c513f43ce5a8c9034608ea584a255.tar.xz
x86/gart: Exclude GART aperture from vmcore
On machines where the GART aperture is mapped over physical RAM /proc/vmcore contains the remapped range and reading it may cause hangs or reboots. In the past, the GART region was added into the resource map, implemented by commit 56dd669a138c ("[PATCH] Insert GART region into resource map") However, inserting the iomem_resource from the early GART code caused resource conflicts with some AGP drivers (bko#72201), which got avoided by reverting the patch in commit 707d4eefbdb3 ("Revert [PATCH] Insert GART region into resource map"). This revert introduced the /proc/vmcore bug. The vmcore ELF header is either prepared by the kernel (when using the kexec_file_load syscall) or by the kexec userspace (when using the kexec_load syscall). Since we no longer have the GART iomem resource, the userspace kexec has no way of knowing which region to exclude from the ELF header. Changes from v1 of this patch: Instead of excluding the aperture from the ELF header, this patch makes /proc/vmcore return zeroes in the second kernel when attempting to read the aperture region. This is done by reusing the gart_oldmem_pfn_is_ram infrastructure originally intended to exclude XEN balooned memory. This works for both, the kexec_file_load and kexec_load syscalls. [Note that the GART region is the same in the first and second kernels: regardless whether the first kernel fixed up the northbridge/bios setting and mapped the aperture over physical memory, the second kernel finds the northbridge properly configured by the first kernel and the aperture never overlaps with e820 memory because the second kernel has a fake e820 map created from the crashkernel memory regions. Thus, the second kernel keeps the aperture address/size as configured by the first kernel.] register_oldmem_pfn_is_ram can only register one callback and returns an error if the callback has been registered already. Since XEN used to be the only user of this function, it never checks the return value. Now that we have more than one user, I added a WARN_ON just in case agp, XEN, or any other future user of register_oldmem_pfn_is_ram were to step on each other's toes. Fixes: 707d4eefbdb3 ("Revert [PATCH] Insert GART region into resource map") Signed-off-by: Jiri Bohac <jbohac@suse.cz> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Baoquan He <bhe@redhat.com> Cc: Toshi Kani <toshi.kani@hpe.com> Cc: David Airlie <airlied@linux.ie> Cc: yinghai@kernel.org Cc: joro@8bytes.org Cc: kexec@lists.infradead.org Cc: Borislav Petkov <bp@alien8.de> Cc: Bjorn Helgaas <bhelgaas@google.com> Cc: Dave Young <dyoung@redhat.com> Cc: Vivek Goyal <vgoyal@redhat.com> Link: https://lkml.kernel.org/r/20180106010013.73suskgxm7lox7g6@dwarf.suse.cz
Diffstat (limited to 'arch/x86/xen')
-rw-r--r--arch/x86/xen/mmu_hvm.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/xen/mmu_hvm.c b/arch/x86/xen/mmu_hvm.c
index 2cfcfe4f6b2a..dd2ad82eee80 100644
--- a/arch/x86/xen/mmu_hvm.c
+++ b/arch/x86/xen/mmu_hvm.c
@@ -75,6 +75,6 @@ void __init xen_hvm_init_mmu_ops(void)
if (is_pagetable_dying_supported())
pv_mmu_ops.exit_mmap = xen_hvm_exit_mmap;
#ifdef CONFIG_PROC_VMCORE
- register_oldmem_pfn_is_ram(&xen_oldmem_pfn_is_ram);
+ WARN_ON(register_oldmem_pfn_is_ram(&xen_oldmem_pfn_is_ram));
#endif
}