Hello Xunlei,
On Sat, 2 Apr 2016 09:23:50 +0800
Xunlei Pang <xpang at redhat.com> wrote:
> On 2016/04/02 at 01:41, Michael Holzheu wrote:
> > Hello Xunlei again,
> >
> > Some initial comments below...
> >
> > On Wed, 30 Mar 2016 19:47:21 +0800
> > Xunlei Pang <xlpang at redhat.com> wrote:
> >
[snip]
> >> + os_info_crashkernel_add(0, 0);
> >> + }
> >> +}
> > Please do not move these functions in the file. If you leave it at their
> > old location, the patch will be *much* smaller.
>
> In fact, I did this wanting avoiding adding extra declaration.
IMHO no extra declaration is necessary (see patch below).
[snip]
> >> +/*
> >> * PM notifier callback for kdump
> >> */
> >> static int machine_kdump_pm_cb(struct notifier_block *nb, unsigned long action,
> >> @@ -43,12 +89,12 @@ static int machine_kdump_pm_cb(struct notifier_block *nb, unsigned long action,
> >> switch (action) {
> >> case PM_SUSPEND_PREPARE:
> >> case PM_HIBERNATION_PREPARE:
> >> - if (crashk_res.start)
> >> + if (kexec_crash_image)
> > Why this change?
>
> arch_kexec_protect_crashkres() will do the unmapping once kdump kernel is loaded
> (i.e. kexec_crash_image is non-NULL), so we should check "kexec_crash_image" here
> and do the corresponding re-mapping.
>
> NULL crashk_res_image means that kdump kernel is not loaded, in this case mapping is
> already setup either initially in reserve_crashkernel() or by arch_kexec_unprotect_crashkres().
Sorry, I missed this obvious part. So your change seems to be ok here.
There is another problem with your patch: The vmem_remove_mapping() function
can only remove mappings which have been added by vmem_add_mapping() before.
Therefore currently the vmem_remove_mapping() call is a nop and we still have
a RW mapping after the kexec system call.
If you check "/sys/kernel/debug/kernel_page_tables" you will see that the
crashkernel memory is still mapped RW after loading kdump.
To fix this we could keep the memblock_remove() and call vmem_add_mapping()
from a init function (see patch below).
[snip]
> >> --- a/arch/s390/kernel/setup.c
> >> +++ b/arch/s390/kernel/setup.c
> >> @@ -603,7 +603,7 @@ static void __init reserve_crashkernel(void)
> >> crashk_res.start = crash_base;
> >> crashk_res.end = crash_base + crash_size - 1;
> >> insert_resource(&iomem_resource, &crashk_res);
> >> - memblock_remove(crash_base, crash_size);
> >> + memblock_reserve(crash_base, crash_size);
> > I will discuss this next week in our team.
>
> This can address the bad page warning when shrinking crashk_res.
Yes, shrinking crashkernel memory is currently broken on s390. Heiko Carstens
(on cc) plans to do some general rework that probably will automatically fix
this issue.
So I would suggest that you merge the following with your initial patch and
then resend the merged patch.
What do you think?
Michael
---------------8<----
s390/kdump: Consolidate crash_map/unmap_reserved_pages() - update
- Move functions back to keep the patch small
- Consolidate crash_map_reserved_pages/arch_kexec_unprotect_crashkres()
- Re-introduce memblock_remove()
- Call arch_kexec_unprotect_crashkres() in machine_kdump_pm_init()
Signed-off-by: Michael Holzheu <holzheu at linux.vnet.ibm.com>
---
arch/s390/kernel/machine_kexec.c | 88 +++++++++++++++++----------------------
1 file changed, 40 insertions(+), 48 deletions(-)
--- a/arch/s390/kernel/machine_kexec.c
+++ b/arch/s390/kernel/machine_kexec.c
@@ -35,52 +35,6 @@ extern const unsigned long long relocate
#ifdef CONFIG_CRASH_DUMP
/*
- * Map or unmap crashkernel memory
- */
-static void crash_map_pages(int enable)
-{
- unsigned long size = resource_size(&crashk_res);
-
- BUG_ON(crashk_res.start % KEXEC_CRASH_MEM_ALIGN ||
- size % KEXEC_CRASH_MEM_ALIGN);
- if (enable)
- vmem_add_mapping(crashk_res.start, size);
- else {
- vmem_remove_mapping(crashk_res.start, size);
- if (size)
- os_info_crashkernel_add(crashk_res.start, size);
- else
- os_info_crashkernel_add(0, 0);
- }
-}
-
-/*
- * Map crashkernel memory
- */
-static void crash_map_reserved_pages(void)
-{
- crash_map_pages(1);
-}
-
-/*
- * Unmap crashkernel memory
- */
-static void crash_unmap_reserved_pages(void)
-{
- crash_map_pages(0);
-}
-
-void arch_kexec_protect_crashkres(void)
-{
- crash_unmap_reserved_pages();
-}
-
-void arch_kexec_unprotect_crashkres(void)
-{
- crash_map_reserved_pages();
-}
-
-/*
* PM notifier callback for kdump
*/
static int machine_kdump_pm_cb(struct notifier_block *nb, unsigned long action,
@@ -90,12 +44,12 @@ static int machine_kdump_pm_cb(struct no
case PM_SUSPEND_PREPARE:
case PM_HIBERNATION_PREPARE:
if (kexec_crash_image)
- crash_map_reserved_pages();
+ arch_kexec_unprotect_crashkres();
break;
case PM_POST_SUSPEND:
case PM_POST_HIBERNATION:
if (kexec_crash_image)
- crash_unmap_reserved_pages();
+ arch_kexec_protect_crashkres();
break;
default:
return NOTIFY_DONE;
@@ -106,6 +60,8 @@ static int machine_kdump_pm_cb(struct no
static int __init machine_kdump_pm_init(void)
{
pm_notifier(machine_kdump_pm_cb, 0);
+ /* Create initial mapping for crashkernel memory */
+ arch_kexec_unprotect_crashkres();
return 0;
}
arch_initcall(machine_kdump_pm_init);
@@ -193,6 +149,42 @@ static int kdump_csum_valid(struct kimag
}
/*
+ * Map or unmap crashkernel memory
+ */
+static void crash_map_pages(int enable)
+{
+ unsigned long size = resource_size(&crashk_res);
+
+ BUG_ON(crashk_res.start % KEXEC_CRASH_MEM_ALIGN ||
+ size % KEXEC_CRASH_MEM_ALIGN);
+ if (enable)
+ vmem_add_mapping(crashk_res.start, size);
+ else {
+ vmem_remove_mapping(crashk_res.start, size);
+ if (size)
+ os_info_crashkernel_add(crashk_res.start, size);
+ else
+ os_info_crashkernel_add(0, 0);
+ }
+}
+
+/*
+ * Unmap crashkernel memory
+ */
+void arch_kexec_protect_crashkres(void)
+{
+ crash_map_pages(0);
+}
+
+/*
+ * Map crashkernel memory
+ */
+void arch_kexec_unprotect_crashkres(void)
+{
+ crash_map_pages(1);
+}
+
+/*
* Give back memory to hypervisor before new kdump is loaded
*/
static int machine_kexec_prepare_kdump(void)
