* Chen Yu <yu.c.c...@intel.com> wrote:
> Sometimes the resuming of hibernation might fail, because the
> system before/after hibernation have different number of page
> frames, and in current implementation, this situation will be
> regarded as invalud resuming process. However, consider the following
> scenario: The resuming system has a larger memory capacity than
> the one before hibernation, and the former memory region is a
> superset of the latter, it should be allowed to resume. For example,
> someone plugs more DRAMs before resuming from hibernation.
> Here's a case for this situation:
>
> e820 memory map before hibernation:
> BIOS-e820: [mem 0x0000000020200000-0x0000000077517fff] usable
> BIOS-e820: [mem 0x0000000077518000-0x0000000077567fff] reserved
>
> e820 memory map during resuming:
> BIOS-e820: [mem 0x0000000020200000-0x000000007753ffff] usable
> BIOS-e820: [mem 0x0000000077540000-0x0000000077567fff] reserved
>
> In current code, the resuming process will be terminated, because
> they have different memory size(usable region), but actually we should
> let it continue to resume because [0x0000000020200000-0x000000007753ffff]
> is a superset of [0x0000000020200000-0x0000000077517fff].
>
> This patch removes the constraint that number of page frames should
> be strictly the same before/after hibernation.
>
> Note: This patch can only work after:
> Commit ec93ef809f34 ("PM / hibernate: avoid unsafe pages in e820
> reserved regions") applied.
>
> Signed-off-by: Chen Yu <yu.c.c...@intel.com>
> ---
> kernel/power/snapshot.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
> index c24d5a2..5b1a071 100644
> --- a/kernel/power/snapshot.c
> +++ b/kernel/power/snapshot.c
> @@ -2072,8 +2072,12 @@ static int check_header(struct swsusp_info *info)
> char *reason;
>
> reason = check_image_kernel(info);
> - if (!reason && info->num_physpages != get_num_physpages())
> - reason = "memory size";
> + /*
> + * No need to check num_physpages with get_num_physpages
> + * as we did before(please refer to git log), because
> + * is_nosave_page will ensure that each page is safe
> + * to be restored.
> + */
> if (reason) {
> printk(KERN_ERR "PM: Image mismatch: %s\n", reason);
> return -EPERM;
No, this removes a useful sanity check that protects against data corruption.
If you want to relax it then you should add code that checks whether the
before/after memory image is truly a superset of each other, and warn and deny
the
hibernation in any other case. (For example when RAM got removed or moved.)
Thanks,
Ingo
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