In commit ec776ef6bbe1 "x86/mm: Add support for the non-standard
protected e820 type" Christoph references the original patch I wrote
implementing pmem support.  The intent of the 'max_pfn' changes in that
commit were to enable persistent memory ranges to be covered by the
struct page memmap by default.  However, that approach was abandoned
when Christoph ported the patches [1], and that functionality has since
been replaced by devm_memremap_pages().

In the meantime, this max_pfn manipulation is confusing kdump [2] that
assumes that everything covered by the max_pfn is "System RAM".  This
results in kdump hanging or crashing.

[1]: https://lists.01.org/pipermail/linux-nvdimm/2015-March/000348.html
[2]: https://bugzilla.redhat.com/show_bug.cgi?id=1351098

Cc: Christoph Hellwig <h...@lst.de>
Cc: Ross Zwisler <ross.zwis...@linux.intel.com>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Boaz Harrosh <b...@plexistor.com>
Cc: H. Peter Anvin <h...@zytor.com>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Ingo Molnar <mi...@kernel.org>
Reported-by: Zhang Yi <yiz...@redhat.com>
Reported-by: Jeff Moyer <jmo...@redhat.com>
Tested-by: Zhang Yi <yiz...@redhat.com>
Fixes: ec776ef6bbe1 ("x86/mm: Add support for the non-standard protected e820 
type")
Signed-off-by: Dan Williams <dan.j.willi...@intel.com>
---
 arch/x86/kernel/e820.c |   14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index 621b501f8935..8a90f1517837 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -348,7 +348,7 @@ int __init sanitize_e820_map(struct e820entry *biosmap, int 
max_nr_map,
                 * continue building up new bios map based on this
                 * information
                 */
-               if (current_type != last_type || current_type == E820_PRAM) {
+               if (current_type != last_type) {
                        if (last_type != 0)      {
                                new_bios[new_bios_entry].size =
                                        change_point[chgidx]->addr - last_addr;
@@ -754,7 +754,7 @@ u64 __init early_reserve_e820(u64 size, u64 align)
 /*
  * Find the highest page frame number we have available
  */
-static unsigned long __init e820_end_pfn(unsigned long limit_pfn)
+static unsigned long __init e820_end_pfn(unsigned long limit_pfn, unsigned 
type)
 {
        int i;
        unsigned long last_pfn = 0;
@@ -765,11 +765,7 @@ static unsigned long __init e820_end_pfn(unsigned long 
limit_pfn)
                unsigned long start_pfn;
                unsigned long end_pfn;
 
-               /*
-                * Persistent memory is accounted as ram for purposes of
-                * establishing max_pfn and mem_map.
-                */
-               if (ei->type != E820_RAM && ei->type != E820_PRAM)
+               if (ei->type != type)
                        continue;
 
                start_pfn = ei->addr >> PAGE_SHIFT;
@@ -794,12 +790,12 @@ static unsigned long __init e820_end_pfn(unsigned long 
limit_pfn)
 }
 unsigned long __init e820_end_of_ram_pfn(void)
 {
-       return e820_end_pfn(MAX_ARCH_PFN);
+       return e820_end_pfn(MAX_ARCH_PFN, E820_RAM);
 }
 
 unsigned long __init e820_end_of_low_ram_pfn(void)
 {
-       return e820_end_pfn(1UL << (32-PAGE_SHIFT));
+       return e820_end_pfn(1UL << (32 - PAGE_SHIFT), E820_RAM);
 }
 
 static void early_panic(char *msg)

Reply via email to