| Message ID | 20200424081218.6919-1-david@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v1] s390: drop memory notifier for protecting kdump crash kernel area | expand |
On 24.04.20 10:12, David Hildenbrand wrote: > Assume we have a crashkernel area of 256MB reserved: > > root@vm0:~# cat /proc/iomem > 00000000-6fffffff : System RAM > 0f258000-0fcfffff : Kernel code > 0fd00000-101d10e3 : Kernel data > 105b3000-1068dfff : Kernel bss > 70000000-7fffffff : Crash kernel > > This exactly corresponds to memory block 7 (memory block size is 256MB). > Trying to offline that memory block results in: > > root@vm0:~# echo "offline" > /sys/devices/system/memory/memory7/state > -bash: echo: write error: Device or resource busy > > [ 128.458762] page:000003d081c00000 refcount:1 mapcount:0 mapping:00000000d01cecd4 index:0x0 > [ 128.458773] flags: 0x1ffff00000001000(reserved) > [ 128.458781] raw: 1ffff00000001000 000003d081c00008 000003d081c00008 0000000000000000 > [ 128.458781] raw: 0000000000000000 0000000000000000 ffffffff00000001 0000000000000000 > [ 128.458783] page dumped because: unmovable page > > The craskernel area is marked reserved in the bootmem allocator. This > results in the memmap getting initialized (refcount=1, PG_reserved), but > the pages are never freed to the page allocator. > > So these pages look like allocated pages that are unmovable (esp. > PG_reserved), and therefore, memory offlining fails early, when trying to > isolate the page range. > > We don't need a special memory notifier and can drop it. Repeating the > above test with this patch results in the same behavior. > > Cc: Heiko Carstens <heiko.carstens@de.ibm.com> > Cc: Vasily Gorbik <gor@linux.ibm.com> > Cc: Christian Borntraeger <borntraeger@de.ibm.com> > Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> > Cc: Philipp Rudo <prudo@linux.ibm.com> > Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com> > Cc: Eric W. Biederman <ebiederm@xmission.com> > Cc: Michal Hocko <mhocko@kernel.org> > Signed-off-by: David Hildenbrand <david@redhat.com> > --- > arch/s390/kernel/setup.c | 33 --------------------------------- > 1 file changed, 33 deletions(-) > > diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c > index 0f0b140b5558..95d4fba0d811 100644 > --- a/arch/s390/kernel/setup.c > +++ b/arch/s390/kernel/setup.c > @@ -39,7 +39,6 @@ > #include <linux/kernel_stat.h> > #include <linux/dma-contiguous.h> > #include <linux/device.h> > -#include <linux/notifier.h> > #include <linux/pfn.h> > #include <linux/ctype.h> > #include <linux/reboot.h> > @@ -591,35 +590,6 @@ static void __init setup_memory_end(void) > pr_notice("The maximum memory size is %luMB\n", memory_end >> 20); > } > > -#ifdef CONFIG_CRASH_DUMP > - > -/* > - * When kdump is enabled, we have to ensure that no memory from > - * the area [0 - crashkernel memory size] and > - * [crashk_res.start - crashk_res.end] is set offline. > - */ Re-reading that comment, I missed the [0 - crashkernel memory size] part (for relocation IIRC). So we might want to keep checking for [0 - crashkernel memory size] - will double check.
diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c index 0f0b140b5558..95d4fba0d811 100644 --- a/arch/s390/kernel/setup.c +++ b/arch/s390/kernel/setup.c @@ -39,7 +39,6 @@ #include <linux/kernel_stat.h> #include <linux/dma-contiguous.h> #include <linux/device.h> -#include <linux/notifier.h> #include <linux/pfn.h> #include <linux/ctype.h> #include <linux/reboot.h> @@ -591,35 +590,6 @@ static void __init setup_memory_end(void) pr_notice("The maximum memory size is %luMB\n", memory_end >> 20); } -#ifdef CONFIG_CRASH_DUMP - -/* - * When kdump is enabled, we have to ensure that no memory from - * the area [0 - crashkernel memory size] and - * [crashk_res.start - crashk_res.end] is set offline. - */ -static int kdump_mem_notifier(struct notifier_block *nb, - unsigned long action, void *data) -{ - struct memory_notify *arg = data; - - if (action != MEM_GOING_OFFLINE) - return NOTIFY_OK; - if (arg->start_pfn < PFN_DOWN(resource_size(&crashk_res))) - return NOTIFY_BAD; - if (arg->start_pfn > PFN_DOWN(crashk_res.end)) - return NOTIFY_OK; - if (arg->start_pfn + arg->nr_pages - 1 < PFN_DOWN(crashk_res.start)) - return NOTIFY_OK; - return NOTIFY_BAD; -} - -static struct notifier_block kdump_mem_nb = { - .notifier_call = kdump_mem_notifier, -}; - -#endif - /* * Make sure that the area behind memory_end is protected */ @@ -703,9 +673,6 @@ static void __init reserve_crashkernel(void) return; } - if (register_memory_notifier(&kdump_mem_nb)) - return; - if (!OLDMEM_BASE && MACHINE_IS_VM) diag10_range(PFN_DOWN(crash_base), PFN_DOWN(crash_size)); crashk_res.start = crash_base;
Assume we have a crashkernel area of 256MB reserved: root@vm0:~# cat /proc/iomem 00000000-6fffffff : System RAM 0f258000-0fcfffff : Kernel code 0fd00000-101d10e3 : Kernel data 105b3000-1068dfff : Kernel bss 70000000-7fffffff : Crash kernel This exactly corresponds to memory block 7 (memory block size is 256MB). Trying to offline that memory block results in: root@vm0:~# echo "offline" > /sys/devices/system/memory/memory7/state -bash: echo: write error: Device or resource busy [ 128.458762] page:000003d081c00000 refcount:1 mapcount:0 mapping:00000000d01cecd4 index:0x0 [ 128.458773] flags: 0x1ffff00000001000(reserved) [ 128.458781] raw: 1ffff00000001000 000003d081c00008 000003d081c00008 0000000000000000 [ 128.458781] raw: 0000000000000000 0000000000000000 ffffffff00000001 0000000000000000 [ 128.458783] page dumped because: unmovable page The craskernel area is marked reserved in the bootmem allocator. This results in the memmap getting initialized (refcount=1, PG_reserved), but the pages are never freed to the page allocator. So these pages look like allocated pages that are unmovable (esp. PG_reserved), and therefore, memory offlining fails early, when trying to isolate the page range. We don't need a special memory notifier and can drop it. Repeating the above test with this patch results in the same behavior. Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Philipp Rudo <prudo@linux.ibm.com> Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com> Cc: Eric W. Biederman <ebiederm@xmission.com> Cc: Michal Hocko <mhocko@kernel.org> Signed-off-by: David Hildenbrand <david@redhat.com> --- arch/s390/kernel/setup.c | 33 --------------------------------- 1 file changed, 33 deletions(-)