[PATCH] crash: Export PAGE_UNACCEPTED_MAPCOUNT_VALUE to vmcoreinfo

[Zhiquan Li]

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.

The 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.  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.

Signed-off-by: Zhiquan Li <zhiquan1.li at intel.com>
---
 kernel/vmcore_info.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/vmcore_info.c b/kernel/vmcore_info.c
index 1fec61603ef3..e066d31d08f8 100644
--- a/kernel/vmcore_info.c
+++ b/kernel/vmcore_info.c
@@ -210,6 +210,10 @@ static int __init crash_save_vmcoreinfo_init(void)
 	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);

base-commit: fc033cf25e612e840e545f8d5ad2edd6ba613ed5
-- 
2.25.1