+ crash-export-page_unaccepted_mapcount_value-to-vmcoreinfo.patch added to mm-nonmm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: crash: export PAGE_UNACCEPTED_MAPCOUNT_VALUE to vmcoreinfo
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     crash-export-page_unaccepted_mapcount_value-to-vmcoreinfo.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/crash-export-page_unaccepted_mapcount_value-to-vmcoreinfo.patch

This patch will later appear in the mm-nonmm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Zhiquan Li <zhiquan1.li@intel.com>
Subject: crash: export PAGE_UNACCEPTED_MAPCOUNT_VALUE to vmcoreinfo
Date: Thu, 3 Apr 2025 11:08:01 +0800

On Intel TDX guest, unaccepted memory is unusable free memory which is not
managed by buddy, until it's accepted by guest.  Before that, it cannot be
accessed by the first kernel as well as the kexec'ed kernel.  The kexec'ed
kernel will skip these pages and fill in zero data for the reader of
vmcore.

A dump tool like makedumpfile creates a page descriptor (size 24 bytes)
for each non-free page, including zero data page, but it will not create
descriptor for free pages.  If it is not able to distinguish these
unaccepted pages with zero data pages, a certain amount of space will be
wasted in proportion (~1/170).  In fact, as a special kind of free page
the unaccepted pages should be excluded, like the real free pages.

Export the page type PAGE_UNACCEPTED_MAPCOUNT_VALUE to vmcoreinfo, so that
dump tool can identify whether a page is unaccepted.

Link: https://lore.kernel.org/all/20240809114854.3745464-5-kirill.shutemov@linux.intel.com/
Link: https://lkml.kernel.org/r/20250403030801.758687-1-zhiquan1.li@intel.com
Signed-off-by: Zhiquan Li <zhiquan1.li@intel.com>
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Baoquan He <bhe@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Zhiquan Li <zhiquan1.li@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 Documentation/admin-guide/kdump/vmcoreinfo.rst |    2 +-
 kernel/vmcore_info.c                           |    4 ++++
 2 files changed, 5 insertions(+), 1 deletion(-)

--- a/Documentation/admin-guide/kdump/vmcoreinfo.rst~crash-export-page_unaccepted_mapcount_value-to-vmcoreinfo
+++ a/Documentation/admin-guide/kdump/vmcoreinfo.rst
@@ -331,7 +331,7 @@ PG_lru|PG_private|PG_swapcache|PG_swapba
 Page attributes. These flags are used to filter various unnecessary for
 dumping pages.
 
-PAGE_BUDDY_MAPCOUNT_VALUE(~PG_buddy)|PAGE_OFFLINE_MAPCOUNT_VALUE(~PG_offline)
+PAGE_BUDDY_MAPCOUNT_VALUE(~PG_buddy)|PAGE_OFFLINE_MAPCOUNT_VALUE(~PG_offline)|PAGE_OFFLINE_MAPCOUNT_VALUE(~PG_unaccepted)
 -----------------------------------------------------------------------------
 
 More page attributes. These flags are used to filter various unnecessary for
--- a/kernel/vmcore_info.c~crash-export-page_unaccepted_mapcount_value-to-vmcoreinfo
+++ a/kernel/vmcore_info.c
@@ -210,6 +210,10 @@ static int __init crash_save_vmcoreinfo_
 	VMCOREINFO_NUMBER(PAGE_HUGETLB_MAPCOUNT_VALUE);
 #define PAGE_OFFLINE_MAPCOUNT_VALUE	(PGTY_offline << 24)
 	VMCOREINFO_NUMBER(PAGE_OFFLINE_MAPCOUNT_VALUE);
+#ifdef CONFIG_UNACCEPTED_MEMORY
+#define PAGE_UNACCEPTED_MAPCOUNT_VALUE	(PGTY_unaccepted << 24)
+	VMCOREINFO_NUMBER(PAGE_UNACCEPTED_MAPCOUNT_VALUE);
+#endif
 
 #ifdef CONFIG_KALLSYMS
 	VMCOREINFO_SYMBOL(kallsyms_names);
_

Patches currently in -mm which might be from zhiquan1.li@intel.com are

crash-export-page_unaccepted_mapcount_value-to-vmcoreinfo.patch