[PATCH v6 24/26] arm64: mte: Save tags when hibernating

[Catalin Marinas]

From: Steven Price <steven.price at arm.com>

When hibernating the contents of all pages in the system are written to
disk, however the MTE tags are not visible to the generic hibernation
code. So just before the hibernation image is created copy the tags out
of the physical tag storage into standard memory so they will be
included in the hibernation image. After hibernation apply the tags back
into the physical tag storage.

Signed-off-by: Steven Price <steven.price at arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas at arm.com>
Cc: James Morse <james.morse at arm.com>
Cc: Will Deacon <will at kernel.org>
---

Notes:
    New in v4.

 arch/arm64/kernel/hibernate.c | 118 ++++++++++++++++++++++++++++++++++
 1 file changed, 118 insertions(+)

diff --git a/arch/arm64/kernel/hibernate.c b/arch/arm64/kernel/hibernate.c
index 68e14152d6e9..23467092e24d 100644
--- a/arch/arm64/kernel/hibernate.c
+++ b/arch/arm64/kernel/hibernate.c
@@ -31,6 +31,7 @@
 #include <asm/kexec.h>
 #include <asm/memory.h>
 #include <asm/mmu_context.h>
+#include <asm/mte.h>
 #include <asm/pgalloc.h>
 #include <asm/pgtable-hwdef.h>
 #include <asm/sections.h>
@@ -285,6 +286,117 @@ static int create_safe_exec_page(void *src_start, size_t length,
 
 #define dcache_clean_range(start, end)	__flush_dcache_area(start, (end - start))
 
+#ifdef CONFIG_ARM64_MTE
+
+static DEFINE_XARRAY(mte_pages);
+
+static int save_tags(struct page *page, unsigned long pfn)
+{
+	void *tag_storage, *ret;
+
+	tag_storage = mte_allocate_tag_storage();
+	if (!tag_storage)
+		return -ENOMEM;
+
+	mte_save_page_tags(page_address(page), tag_storage);
+
+	ret = xa_store(&mte_pages, pfn, tag_storage, GFP_KERNEL);
+	if (WARN(xa_is_err(ret), "Failed to store MTE tags")) {
+		mte_free_tag_storage(tag_storage);
+		return xa_err(ret);
+	} else if (WARN(ret, "swsusp: %s: Duplicate entry", __func__)) {
+		mte_free_tag_storage(ret);
+	}
+
+	return 0;
+}
+
+static void swsusp_mte_free_storage(void)
+{
+	XA_STATE(xa_state, &mte_pages, 0);
+	void *tags;
+
+	xa_lock(&mte_pages);
+	xas_for_each(&xa_state, tags, ULONG_MAX) {
+		mte_free_tag_storage(tags);
+	}
+	xa_unlock(&mte_pages);
+
+	xa_destroy(&mte_pages);
+}
+
+static int swsusp_mte_save_tags(void)
+{
+	struct zone *zone;
+	unsigned long pfn, max_zone_pfn;
+	int ret = 0;
+	int n = 0;
+
+	if (!system_supports_mte())
+		return 0;
+
+	for_each_populated_zone(zone) {
+		max_zone_pfn = zone_end_pfn(zone);
+		for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
+			struct page *page = pfn_to_online_page(pfn);
+
+			if (!page)
+				continue;
+
+			if (!test_bit(PG_mte_tagged, &page->flags))
+				continue;
+
+			ret = save_tags(page, pfn);
+			if (ret) {
+				swsusp_mte_free_storage();
+				goto out;
+			}
+
+			n++;
+		}
+	}
+	pr_info("Saved %d MTE pages\n", n);
+
+out:
+	return ret;
+}
+
+static void swsusp_mte_restore_tags(void)
+{
+	XA_STATE(xa_state, &mte_pages, 0);
+	int n = 0;
+	void *tags;
+
+	xa_lock(&mte_pages);
+	xas_for_each(&xa_state, tags, ULONG_MAX) {
+		unsigned long pfn = xa_state.xa_index;
+		struct page *page = pfn_to_online_page(pfn);
+
+		mte_restore_page_tags(page_address(page), tags);
+
+		mte_free_tag_storage(tags);
+		n++;
+	}
+	xa_unlock(&mte_pages);
+
+	pr_info("Restored %d MTE pages\n", n);
+
+	xa_destroy(&mte_pages);
+}
+
+#else	/* CONFIG_ARM64_MTE */
+
+static int swsusp_mte_save_tags(void)
+{
+	return 0;
+}
+
+static void swsusp_mte_restore_tags(void)
+{
+}
+
+#endif	/* CONFIG_ARM64_MTE */
+
 int swsusp_arch_suspend(void)
 {
 	int ret = 0;
@@ -302,6 +414,10 @@ int swsusp_arch_suspend(void)
 		/* make the crash dump kernel image visible/saveable */
 		crash_prepare_suspend();
 
+		ret = swsusp_mte_save_tags();
+		if (ret)
+			return ret;
+
 		sleep_cpu = smp_processor_id();
 		ret = swsusp_save();
 	} else {
@@ -315,6 +431,8 @@ int swsusp_arch_suspend(void)
 			dcache_clean_range(__hyp_text_start, __hyp_text_end);
 		}
 
+		swsusp_mte_restore_tags();
+
 		/* make the crash dump kernel image protected again */
 		crash_post_resume();