I found that the kdump is broken on linux-4.11.0-rc2+, probably
due to the 5level-paging feature that "#define p4d_present(p4d) 1",
as a result in ident_p4d_init(), it will go into ident_pud_init()
directly without allocating the new pud.
Looks like this patch can make it work again.
Cc: Kirill A. Shutemov <[email protected]>
Signed-off-by: Xunlei Pang <[email protected]>
---
arch/x86/mm/ident_map.c | 22 ++++++++++------------
include/asm-generic/5level-fixup.h | 6 +++---
2 files changed, 13 insertions(+), 15 deletions(-)
diff --git a/arch/x86/mm/ident_map.c b/arch/x86/mm/ident_map.c
index 04210a2..d14bb52 100644
--- a/arch/x86/mm/ident_map.c
+++ b/arch/x86/mm/ident_map.c
@@ -97,22 +97,20 @@ int kernel_ident_mapping_init(struct x86_mapping_info *info, pgd_t *pgd_page,
continue;
}
- p4d = (p4d_t *)info->alloc_pgt_page(info->context);
- if (!p4d)
- return -ENOMEM;
+ if (IS_ENABLED(CONFIG_X86_5LEVEL)) {
+ p4d = (p4d_t *)info->alloc_pgt_page(info->context);
+ if (!p4d)
+ return -ENOMEM;
+ } else {
+ p4d = pgd;
+ }
+
result = ident_p4d_init(info, p4d, addr, next);
if (result)
return result;
- if (IS_ENABLED(CONFIG_X86_5LEVEL)) {
+
+ if (IS_ENABLED(CONFIG_X86_5LEVEL))
set_pgd(pgd, __pgd(__pa(p4d) | _KERNPG_TABLE));
- } else {
- /*
- * With p4d folded, pgd is equal to p4d.
- * The pgd entry has to point to the pud page table in this case.
- */
- pud_t *pud = pud_offset(p4d, 0);
- set_pgd(pgd, __pgd(__pa(pud) | _KERNPG_TABLE));
- }
}
return 0;
diff --git a/include/asm-generic/5level-fixup.h b/include/asm-generic/5level-fixup.h
index b5ca82d..3131ada 100644
--- a/include/asm-generic/5level-fixup.h
+++ b/include/asm-generic/5level-fixup.h
@@ -17,9 +17,9 @@
#define p4d_alloc(mm, pgd, address) (pgd)
#define p4d_offset(pgd, start) (pgd)
-#define p4d_none(p4d) 0
-#define p4d_bad(p4d) 0
-#define p4d_present(p4d) 1
+#define p4d_none(p4d) pgd_none(p4d)
+#define p4d_bad(p4d) pgd_bad(p4d)
+#define p4d_present(p4d) pgd_present(p4d)
#define p4d_ERROR(p4d) do { } while (0)
#define p4d_clear(p4d) pgd_clear(p4d)
#define p4d_val(p4d) pgd_val(p4d)
--
1.8.3.1
On Mon, Mar 20, 2017 at 02:11:31PM +0800, Xunlei Pang wrote:
> I found that the kdump is broken on linux-4.11.0-rc2+
That's actually tip tree or linux-next. The problematic change is not in
Linus' tree.
> , probably
> due to the 5level-paging feature that "#define p4d_present(p4d) 1",
> as a result in ident_p4d_init(), it will go into ident_pud_init()
> directly without allocating the new pud.
>
> Looks like this patch can make it work again.
Okay, that's bisectability issue. Uncovered by splitting my patchset into
parts.
Could you check if applying "Part 2" of 5-level paging changes[1] would
help you?
Making the code work with both <asm-generic/5level-fixup.h> and
<asm-generic/pgtable-nop4d.h> would make it even uglier. Not sure if it
makes sense to address it on its own if second part fixes the situation.
[1] http://lkml.kernel.org/r/[email protected]
--
Kirill A. Shutemov
On 03/24/2017 at 08:04 PM, Kirill A. Shutemov wrote:
> On Mon, Mar 20, 2017 at 02:11:31PM +0800, Xunlei Pang wrote:
>> I found that the kdump is broken on linux-4.11.0-rc2+
> That's actually tip tree or linux-next. The problematic change is not in
> Linus' tree.
>
>> , probably
>> due to the 5level-paging feature that "#define p4d_present(p4d) 1",
>> as a result in ident_p4d_init(), it will go into ident_pud_init()
>> directly without allocating the new pud.
>>
>> Looks like this patch can make it work again.
> Okay, that's bisectability issue. Uncovered by splitting my patchset into
> parts.
>
> Could you check if applying "Part 2" of 5-level paging changes[1] would
> help you?
I confirmed that it works after applying your following patches:
x86: Convert the rest of the code to support p4d_t
x86/xen: Change __xen_pgd_walk() and xen_cleanmfnmap() to support p4d
x86/kasan: Prepare clear_pgds() to switch to <asm-generic/pgtable-nop4d.h>
x86/mm/pat: Add 5-level paging support
x86/efi: Add 5-level paging support
x86/kexec: Add 5-level paging support
Regards,
Xunlei
>
> Making the code work with both <asm-generic/5level-fixup.h> and
> <asm-generic/pgtable-nop4d.h> would make it even uglier. Not sure if it
> makes sense to address it on its own if second part fixes the situation.
>
> [1] http://lkml.kernel.org/r/[email protected]
>
On 03/30/2017 at 07:21 PM, Xunlei Pang wrote:
> On 03/24/2017 at 08:04 PM, Kirill A. Shutemov wrote:
>> On Mon, Mar 20, 2017 at 02:11:31PM +0800, Xunlei Pang wrote:
>>> I found that the kdump is broken on linux-4.11.0-rc2+
>> That's actually tip tree or linux-next. The problematic change is not in
>> Linus' tree.
>>
>>> , probably
>>> due to the 5level-paging feature that "#define p4d_present(p4d) 1",
>>> as a result in ident_p4d_init(), it will go into ident_pud_init()
>>> directly without allocating the new pud.
>>>
>>> Looks like this patch can make it work again.
>> Okay, that's bisectability issue. Uncovered by splitting my patchset into
>> parts.
>>
>> Could you check if applying "Part 2" of 5-level paging changes[1] would
>> help you?
> I confirmed that it works after applying your following patches:
> x86: Convert the rest of the code to support p4d_t
To be exact, this one("x86: Convert the rest of the code to support p4d_t") fixes the issue.
> x86/xen: Change __xen_pgd_walk() and xen_cleanmfnmap() to support p4d
> x86/kasan: Prepare clear_pgds() to switch to <asm-generic/pgtable-nop4d.h>
> x86/mm/pat: Add 5-level paging support
> x86/efi: Add 5-level paging support
> x86/kexec: Add 5-level paging support
>
> Regards,
> Xunlei
>
>> Making the code work with both <asm-generic/5level-fixup.h> and
>> <asm-generic/pgtable-nop4d.h> would make it even uglier. Not sure if it
>> makes sense to address it on its own if second part fixes the situation.
>>
>> [1] http://lkml.kernel.org/r/[email protected]
>>
>
> _______________________________________________
> kexec mailing list
> [email protected]
> http://lists.infradead.org/mailman/listinfo/kexec