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authorLinus Torvalds <torvalds@linux-foundation.org>2018-01-29 18:58:16 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2018-01-29 18:58:16 -0800
commit942633523cde99c5bfa0329996dd839ca66a87aa (patch)
tree7e3c3851caccf1a84239717e0c9c601b7dfd2b08
parent36c289e72a63c3a4fbb14f84e220a2a75a5bf656 (diff)
parent2a3e83c6f96c513f43ce5a8c9034608ea584a255 (diff)
Merge branch 'x86-mm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 mm update from Thomas Gleixner: "A single patch which excludes the GART aperture from vmcore as accessing that area from a dump kernel can crash the kernel. Not necessarily the nicest way to fix this, but curing this from ground up requires a more thorough rewrite of the whole kexec/kdump magic" * 'x86-mm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86/gart: Exclude GART aperture from vmcore
-rw-r--r--arch/x86/kernel/aperture_64.c46
-rw-r--r--arch/x86/xen/mmu_hvm.c2
2 files changed, 46 insertions, 2 deletions
diff --git a/arch/x86/kernel/aperture_64.c b/arch/x86/kernel/aperture_64.c
index f5d92bc3b884..2c4d5ece7456 100644
--- a/arch/x86/kernel/aperture_64.c
+++ b/arch/x86/kernel/aperture_64.c
@@ -30,6 +30,7 @@
#include <asm/dma.h>
#include <asm/amd_nb.h>
#include <asm/x86_init.h>
+#include <linux/crash_dump.h>
/*
* Using 512M as goal, in case kexec will load kernel_big
@@ -56,6 +57,33 @@ int fallback_aper_force __initdata;
int fix_aperture __initdata = 1;
+#ifdef CONFIG_PROC_VMCORE
+/*
+ * If the first kernel maps the aperture over e820 RAM, the kdump kernel will
+ * use the same range because it will remain configured in the northbridge.
+ * Trying to dump this area via /proc/vmcore may crash the machine, so exclude
+ * it from vmcore.
+ */
+static unsigned long aperture_pfn_start, aperture_page_count;
+
+static int gart_oldmem_pfn_is_ram(unsigned long pfn)
+{
+ return likely((pfn < aperture_pfn_start) ||
+ (pfn >= aperture_pfn_start + aperture_page_count));
+}
+
+static void exclude_from_vmcore(u64 aper_base, u32 aper_order)
+{
+ aperture_pfn_start = aper_base >> PAGE_SHIFT;
+ aperture_page_count = (32 * 1024 * 1024) << aper_order >> PAGE_SHIFT;
+ WARN_ON(register_oldmem_pfn_is_ram(&gart_oldmem_pfn_is_ram));
+}
+#else
+static void exclude_from_vmcore(u64 aper_base, u32 aper_order)
+{
+}
+#endif
+
/* This code runs before the PCI subsystem is initialized, so just
access the northbridge directly. */
@@ -435,8 +463,16 @@ int __init gart_iommu_hole_init(void)
out:
if (!fix && !fallback_aper_force) {
- if (last_aper_base)
+ if (last_aper_base) {
+ /*
+ * If this is the kdump kernel, the first kernel
+ * may have allocated the range over its e820 RAM
+ * and fixed up the northbridge
+ */
+ exclude_from_vmcore(last_aper_base, last_aper_order);
+
return 1;
+ }
return 0;
}
@@ -473,6 +509,14 @@ out:
return 0;
}
+ /*
+ * If this is the kdump kernel _and_ the first kernel did not
+ * configure the aperture in the northbridge, this range may
+ * overlap with the first kernel's memory. We can't access the
+ * range through vmcore even though it should be part of the dump.
+ */
+ exclude_from_vmcore(aper_alloc, aper_order);
+
/* Fix up the north bridges */
for (i = 0; i < amd_nb_bus_dev_ranges[i].dev_limit; i++) {
int bus, dev_base, dev_limit;
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
}

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