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From:   Heiko Carstens <hca@linux.ibm.com>
To:     Marco Elver <elver@google.com>,
        Alexander Potapenko <glider@google.com>
Cc:     Sven Schnelle <svens@linux.ibm.com>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Christian Borntraeger <borntraeger@de.ibm.com>,
        kasan-dev@googlegroups.com, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org
Subject: [PATCH 1/4] s390/mm: implement set_memory_4k()
Date:   Wed, 28 Jul 2021 21:02:51 +0200
Message-Id: <20210728190254.3921642-2-hca@linux.ibm.com>
In-Reply-To: <20210728190254.3921642-1-hca@linux.ibm.com>
References: <20210728190254.3921642-1-hca@linux.ibm.com>
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Implement set_memory_4k() which will split any present large or huge
mapping in the given range to a 4k mapping.

Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
---
 arch/s390/include/asm/set_memory.h |  6 ++++++
 arch/s390/mm/pageattr.c            | 12 ++++++++++--
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/arch/s390/include/asm/set_memory.h b/arch/s390/include/asm/set_memory.h
index a22a5a81811c..950d87bd997a 100644
--- a/arch/s390/include/asm/set_memory.h
+++ b/arch/s390/include/asm/set_memory.h
@@ -10,6 +10,7 @@ extern struct mutex cpa_mutex;
 #define SET_MEMORY_RW	2UL
 #define SET_MEMORY_NX	4UL
 #define SET_MEMORY_X	8UL
+#define SET_MEMORY_4K  16UL
 
 int __set_memory(unsigned long addr, int numpages, unsigned long flags);
 
@@ -33,4 +34,9 @@ static inline int set_memory_x(unsigned long addr, int numpages)
 	return __set_memory(addr, numpages, SET_MEMORY_X);
 }
 
+static inline int set_memory_4k(unsigned long addr, int numpages)
+{
+	return __set_memory(addr, numpages, SET_MEMORY_4K);
+}
+
 #endif
diff --git a/arch/s390/mm/pageattr.c b/arch/s390/mm/pageattr.c
index ed8e5b3575d5..b09fd5c7f85f 100644
--- a/arch/s390/mm/pageattr.c
+++ b/arch/s390/mm/pageattr.c
@@ -155,6 +155,7 @@ static int walk_pmd_level(pud_t *pudp, unsigned long addr, unsigned long end,
 			  unsigned long flags)
 {
 	unsigned long next;
+	int need_split;
 	pmd_t *pmdp;
 	int rc = 0;
 
@@ -164,7 +165,10 @@ static int walk_pmd_level(pud_t *pudp, unsigned long addr, unsigned long end,
 			return -EINVAL;
 		next = pmd_addr_end(addr, end);
 		if (pmd_large(*pmdp)) {
-			if (addr & ~PMD_MASK || addr + PMD_SIZE > next) {
+			need_split  =  (flags & SET_MEMORY_4K) != 0;
+			need_split |= (addr & ~PMD_MASK) != 0;
+			need_split |= addr + PMD_SIZE > next;
+			if (need_split) {
 				rc = split_pmd_page(pmdp, addr);
 				if (rc)
 					return rc;
@@ -232,6 +236,7 @@ static int walk_pud_level(p4d_t *p4d, unsigned long addr, unsigned long end,
 			  unsigned long flags)
 {
 	unsigned long next;
+	int need_split;
 	pud_t *pudp;
 	int rc = 0;
 
@@ -241,7 +246,10 @@ static int walk_pud_level(p4d_t *p4d, unsigned long addr, unsigned long end,
 			return -EINVAL;
 		next = pud_addr_end(addr, end);
 		if (pud_large(*pudp)) {
-			if (addr & ~PUD_MASK || addr + PUD_SIZE > next) {
+			need_split  = (flags & SET_MEMORY_4K) != 0;
+			need_split |= (addr & ~PUD_MASK) != 0;
+			need_split |= addr + PUD_SIZE > next;
+			if (need_split) {
 				rc = split_pud_page(pudp, addr);
 				if (rc)
 					break;
-- 
2.25.1