This is a note to let you know that I've just added the patch titled
mm: don't defer struct page initialization for Xen pv guests
to the 4.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: mm-don-t-defer-struct-page-initialization-for-xen-pv-guests.patch and it can be found in the queue-4.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From 895f7b8e90200cf1a5dc313329369adf30e51f9a Mon Sep 17 00:00:00 2001
From: Juergen Gross jgross@suse.com Date: Wed, 21 Feb 2018 14:46:09 -0800 Subject: mm: don't defer struct page initialization for Xen pv guests
From: Juergen Gross jgross@suse.com
commit 895f7b8e90200cf1a5dc313329369adf30e51f9a upstream.
Commit f7f99100d8d9 ("mm: stop zeroing memory during allocation in vmemmap") broke Xen pv domains in some configurations, as the "Pinned" information in struct page of early page tables could get lost.
This will lead to the kernel trying to write directly into the page tables instead of asking the hypervisor to do so. The result is a crash like the following:
BUG: unable to handle kernel paging request at ffff8801ead19008 IP: xen_set_pud+0x4e/0xd0 PGD 1c0a067 P4D 1c0a067 PUD 23a0067 PMD 1e9de0067 PTE 80100001ead19065 Oops: 0003 [#1] PREEMPT SMP Modules linked in: CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.14.0-default+ #271 Hardware name: Dell Inc. Latitude E6440/0159N7, BIOS A07 06/26/2014 task: ffffffff81c10480 task.stack: ffffffff81c00000 RIP: e030:xen_set_pud+0x4e/0xd0 Call Trace: __pmd_alloc+0x128/0x140 ioremap_page_range+0x3f4/0x410 __ioremap_caller+0x1c3/0x2e0 acpi_os_map_iomem+0x175/0x1b0 acpi_tb_acquire_table+0x39/0x66 acpi_tb_validate_table+0x44/0x7c acpi_tb_verify_temp_table+0x45/0x304 acpi_reallocate_root_table+0x12d/0x141 acpi_early_init+0x4d/0x10a start_kernel+0x3eb/0x4a1 xen_start_kernel+0x528/0x532 Code: 48 01 e8 48 0f 42 15 a2 fd be 00 48 01 d0 48 ba 00 00 00 00 00 ea ff ff 48 c1 e8 0c 48 c1 e0 06 48 01 d0 48 8b 00 f6 c4 02 75 5d <4c> 89 65 00 5b 5d 41 5c c3 65 8b 05 52 9f fe 7e 89 c0 48 0f a3 RIP: xen_set_pud+0x4e/0xd0 RSP: ffffffff81c03cd8 CR2: ffff8801ead19008 ---[ end trace 38eca2e56f1b642e ]---
Avoid this problem by not deferring struct page initialization when running as Xen pv guest.
Pavel said:
: This is unique for Xen, so this particular issue won't effect other : configurations. I am going to investigate if there is a way to : re-enable deferred page initialization on xen guests.
[akpm@linux-foundation.org: explicitly include xen.h] Link: http://lkml.kernel.org/r/20180216154101.22865-1-jgross@suse.com Fixes: f7f99100d8d95d ("mm: stop zeroing memory during allocation in vmemmap") Signed-off-by: Juergen Gross jgross@suse.com Reviewed-by: Pavel Tatashin pasha.tatashin@oracle.com Cc: Steven Sistare steven.sistare@oracle.com Cc: Daniel Jordan daniel.m.jordan@oracle.com Cc: Bob Picco bob.picco@oracle.com Cc: stable@vger.kernel.org [4.15.x] Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- mm/page_alloc.c | 4 ++++ 1 file changed, 4 insertions(+)
--- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -46,6 +46,7 @@ #include <linux/stop_machine.h> #include <linux/sort.h> #include <linux/pfn.h> +#include <xen/xen.h> #include <linux/backing-dev.h> #include <linux/fault-inject.h> #include <linux/page-isolation.h> @@ -347,6 +348,9 @@ static inline bool update_defer_init(pg_ /* Always populate low zones for address-contrained allocations */ if (zone_end < pgdat_end_pfn(pgdat)) return true; + /* Xen PV domains need page structures early */ + if (xen_pv_domain()) + return true; (*nr_initialised)++; if ((*nr_initialised > pgdat->static_init_pgcnt) && (pfn & (PAGES_PER_SECTION - 1)) == 0) {
Patches currently in stable-queue which might be from jgross@suse.com are
queue-4.15/mm-don-t-defer-struct-page-initialization-for-xen-pv-guests.patch queue-4.15/mm-swap-frontswap-fix-thp-swap-if-frontswap-enabled.patch