linux-kernel - [PATCH V10 26/44] memremap_pages: Introduce pgmap_protection

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Date:   Tue, 19 Apr 2022 10:06:31 -0700
From:   ira.weiny@...el.com
To:     Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Dan Williams <dan.j.williams@...el.com>
Cc:     Ira Weiny <ira.weiny@...el.com>, Fenghua Yu <fenghua.yu@...el.com>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        "Shankar, Ravi V" <ravi.v.shankar@...el.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH V10 26/44] memremap_pages: Introduce pgmap_protection_available()

From: Ira Weiny <ira.weiny@...el.com>

PMEM will flag additional dev_pagemap protection through (struct
dev_pagemap)->flags.  However, it is more efficient to know if that
protection is available prior to requesting it and failing the mapping.

Define pgmap_protection_available() to check if protection is available
prior to being requested.  The name of pgmap_protection_available() was
specifically chosen to isolate the implementation of the protection from
higher level users.

Signed-off-by: Ira Weiny <ira.weiny@...el.com>

---
Changes for V10
	Move code from mm.h to memremap.h
		Upstream separated memremap.h functionality from mm.h
		dc90f0846df4 ("mm: don't include <linux/memremap.h> in <linux/mm.h>")

Changes for V9
	Clean up commit message
	From Dan Williams
		make call stack static inline throughout this call and
			pks_available() such that callers calls
			cpu_feature_enabled() directly

Changes for V8
	Split this out to it's own patch.
	s/pgmap_protection_enabled/pgmap_protection_available
---
 include/linux/memremap.h | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/include/linux/memremap.h b/include/linux/memremap.h
index 8af304f6b504..7980d0db8617 100644
--- a/include/linux/memremap.h
+++ b/include/linux/memremap.h
@@ -6,6 +6,7 @@
 #include <linux/range.h>
 #include <linux/ioport.h>
 #include <linux/percpu-refcount.h>
+#include <linux/pks.h>
 
 struct resource;
 struct device;
@@ -214,4 +215,20 @@ static inline void put_dev_pagemap(struct dev_pagemap *pgmap)
 		percpu_ref_put(&pgmap->ref);
 }
 
+#ifdef CONFIG_DEVMAP_ACCESS_PROTECTION
+
+static inline bool pgmap_protection_available(void)
+{
+	return pks_available();
+}
+
+#else
+
+static inline bool pgmap_protection_available(void)
+{
+	return false;
+}
+
+#endif /* CONFIG_DEVMAP_ACCESS_PROTECTION */
+
 #endif /* _LINUX_MEMREMAP_H_ */
-- 
2.35.1