linux-kernel - [RFC V2 13/37] mm, dmem: introduce PFN_DMEM and pfn_t

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Message-Id: <e0da248a3c9eab661f9302ea153be286874634da.1607332046.git.yuleixzhang@tencent.com>
Date:   Mon,  7 Dec 2020 19:31:06 +0800
From:   yulei.kernel@...il.com
To:     linux-mm@...ck.org, akpm@...ux-foundation.org,
        linux-fsdevel@...r.kernel.org, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, naoya.horiguchi@....com,
        viro@...iv.linux.org.uk, pbonzini@...hat.com
Cc:     joao.m.martins@...cle.com, rdunlap@...radead.org,
        sean.j.christopherson@...el.com, xiaoguangrong.eric@...il.com,
        kernellwp@...il.com, lihaiwei.kernel@...il.com,
        Yulei Zhang <yuleixzhang@...cent.com>,
        Chen Zhuo <sagazchen@...cent.com>
Subject: [RFC V2 13/37] mm, dmem: introduce PFN_DMEM and pfn_t_dmem

From: Yulei Zhang <yuleixzhang@...cent.com>

Introduce PFN_DMEM as a new pfn flag for dmem pfn, define it
by setting (BITS_PER_LONG_LONG - 6) bit.

Introduce pfn_t_dmem() helper to recognize dmem pfn.

Signed-off-by: Chen Zhuo <sagazchen@...cent.com>
Signed-off-by: Yulei Zhang <yuleixzhang@...cent.com>
---
 include/linux/pfn_t.h | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/include/linux/pfn_t.h b/include/linux/pfn_t.h
index 2d91482..c6c0f1f 100644
--- a/include/linux/pfn_t.h
+++ b/include/linux/pfn_t.h
@@ -11,6 +11,7 @@
  * PFN_MAP - pfn has a dynamic page mapping established by a device driver
  * PFN_SPECIAL - for CONFIG_FS_DAX_LIMITED builds to allow XIP, but not
  *		 get_user_pages
+ * PFN_DMEM - pfn references a dmem page
  */
 #define PFN_FLAGS_MASK (((u64) (~PAGE_MASK)) << (BITS_PER_LONG_LONG - PAGE_SHIFT))
 #define PFN_SG_CHAIN (1ULL << (BITS_PER_LONG_LONG - 1))
@@ -18,13 +19,15 @@
 #define PFN_DEV (1ULL << (BITS_PER_LONG_LONG - 3))
 #define PFN_MAP (1ULL << (BITS_PER_LONG_LONG - 4))
 #define PFN_SPECIAL (1ULL << (BITS_PER_LONG_LONG - 5))
+#define PFN_DMEM (1ULL << (BITS_PER_LONG_LONG - 6))
 
 #define PFN_FLAGS_TRACE \
 	{ PFN_SPECIAL,	"SPECIAL" }, \
 	{ PFN_SG_CHAIN,	"SG_CHAIN" }, \
 	{ PFN_SG_LAST,	"SG_LAST" }, \
 	{ PFN_DEV,	"DEV" }, \
-	{ PFN_MAP,	"MAP" }
+	{ PFN_MAP,	"MAP" }, \
+	{ PFN_DMEM,	"DMEM" }
 
 static inline pfn_t __pfn_to_pfn_t(unsigned long pfn, u64 flags)
 {
@@ -128,4 +131,16 @@ static inline bool pfn_t_special(pfn_t pfn)
 	return false;
 }
 #endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */
+
+#ifdef CONFIG_ARCH_HAS_PTE_DMEM
+static inline bool pfn_t_dmem(pfn_t pfn)
+{
+	return (pfn.val & PFN_DMEM) == PFN_DMEM;
+}
+#else
+static inline bool pfn_t_dmem(pfn_t pfn)
+{
+	return false;
+}
+#endif /* CONFIG_ARCH_HAS_PTE_DMEM */
 #endif /* _LINUX_PFN_T_H_ */
-- 
1.8.3.1