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Subject[GIT pull] x86/mm updates for 4.16
Linus,

please pull the latest x86-mm-for-linus git tree from:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86-mm-for-linus

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.

Thanks,

tglx

------------------>
Jiri Bohac (1):
x86/gart: Exclude GART aperture from vmcore


arch/x86/kernel/aperture_64.c | 46 ++++++++++++++++++++++++++++++++++++++++++-
arch/x86/xen/mmu_hvm.c | 2 +-
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 @@ int __init gart_iommu_hole_init(void)
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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