[PATCH v3 14/21] kho: initialize kho_scratch pointer earlier in boot

[Pratyush Yadav <pratyush@kernel.org>]

From: "Pratyush Yadav (Google)" <pratyush@kernel.org>

In a future patch, mm init will use kho_scratch_overlap() for deciding
the migrate type of pageblocks it initializes. The earliest user
currently is free_area_init(). kho_scratch_overlap()
relies on kho_scratch pointer being initialized. Introduce
kho_memory_init_early() to do this.

kho_populate() would normally be a good place to do this, but
unfortunately, phys_to_virt() does not work at that point on ARM64. So
we need yet another initialization function.

Signed-off-by: Pratyush Yadav (Google) <pratyush@kernel.org>
---
 include/linux/kexec_handover.h     |  3 +++
 kernel/liveupdate/kexec_handover.c | 15 +++++++++++++--
 mm/mm_init.c                       |  1 +
 3 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/include/linux/kexec_handover.h b/include/linux/kexec_handover.h
index 40cb95a80981..18ba417f1ada 100644
--- a/include/linux/kexec_handover.h
+++ b/include/linux/kexec_handover.h
@@ -33,6 +33,7 @@ void kho_remove_subtree(void *blob);
 int kho_retrieve_subtree(const char *name, phys_addr_t *phys, size_t *size);
 
 void kho_memory_init(void);
+void kho_memory_init_early(void);
 
 void kho_populate(phys_addr_t fdt_phys, u64 fdt_len, phys_addr_t scratch_phys,
 		  u64 scratch_len);
@@ -110,6 +111,8 @@ static inline int kho_retrieve_subtree(const char *name, phys_addr_t *phys,
 
 static inline void kho_memory_init(void) { }
 
+static inline void kho_memory_init_early(void) { }
+
 static inline void kho_populate(phys_addr_t fdt_phys, u64 fdt_len,
 				phys_addr_t scratch_phys, u64 scratch_len)
 {
diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c
index b3b97a6ff9c8..2ddfc804cdf7 100644
--- a/kernel/liveupdate/kexec_handover.c
+++ b/kernel/liveupdate/kexec_handover.c
@@ -1534,8 +1534,6 @@ static void __init kho_mem_retrieve(void)
 	const void *fdt = kho_get_fdt();
 	int err;
 
-	kho_scratch = phys_to_virt(kho_in.scratch_phys);
-
 	/*
 	 * kho_get_mem_map() should always succeed. If it fails, kho_populate()
 	 * catches that and never sets kho_in.scratch_phys, which stops memory
@@ -1756,6 +1754,19 @@ static __init int kho_init(void)
 }
 fs_initcall(kho_init);
 
+void __init kho_memory_init_early(void)
+{
+	if (!is_kho_boot())
+		return;
+
+	/*
+	 * kho_scratch_overlap() needs kho_scratch to be initialized. It
+	 * is used by free_area_init() on KHO boots, so initialize it
+	 * early.
+	 */
+	kho_scratch = phys_to_virt(kho_in.scratch_phys);
+}
+
 void __init kho_memory_init(void)
 {
 	if (kho_in.scratch_phys)
diff --git a/mm/mm_init.c b/mm/mm_init.c
index 0f64909e8d20..84d4b1c997bc 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -2687,6 +2687,7 @@ void __init __weak mem_init(void)
 
 void __init mm_core_init_early(void)
 {
+	kho_memory_init_early();
 	hugetlb_cma_reserve();
 	hugetlb_bootmem_alloc();
 
-- 
2.55.0.141.g00534a21ce-goog