s390x/mm: simplify gmap_protect_rmap()

PATCH Applied David Hildenbrand 3 participants 3 messages Jan 23, 2018 – Jan 24, 2018

Subsystems (3)

KVM s390 s390 MM

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David Hildenbrand

author

2018-01-23 21:26 UTC #0 lore raw

PATCH 1/1 s390x/mm: simplify gmap_protect_rmap()

We never call it with anything but PROT_READ. This is a left over from an old prototype. For creation of shadow page tables, we always only have to protect the original table in guest memory from write accesses, so we can properly invalidate the shadow on writes. Other protections are not needed.

Signed-off-by David Hildenbrand <[email protected]>

---
 arch/s390/mm/gmap.c | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

arch/s390/mm/gmap.c +8 -9

index 54cfd51a5a27..a7e05c5dea70 100644
@@ -1021,18 +1021,17 @@ static inline void gmap_insert_rmap(struct gmap *sg, unsigned long vmaddr,
 }
 
 /**
- * gmap_protect_rmap - modify access rights to memory and create an rmap
+ * gmap_protect_rmap - restrict access rights to memory (RO) and create an rmap
  * @sg: pointer to the shadow guest address space structure
  * @raddr: rmap address in the shadow gmap
  * @paddr: address in the parent guest address space
  * @len: length of the memory area to protect
- * @prot: indicates access rights: none, read-only or read-write
  *
  * Returns 0 if successfully protected and the rmap was created, -ENOMEM
  * if out of memory and -EFAULT if paddr is invalid.
  */
 static int gmap_protect_rmap(struct gmap *sg, unsigned long raddr,
-			     unsigned long paddr, unsigned long len, int prot)
+			     unsigned long paddr, unsigned long len)
 {
 	struct gmap *parent;
 	struct gmap_rmap *rmap;

@@ -1060,7 +1059,7 @@ static int gmap_protect_rmap(struct gmap *sg, unsigned long raddr,
 		ptep = gmap_pte_op_walk(parent, paddr, &ptl);
 		if (ptep) {
 			spin_lock(&sg->guest_table_lock);
-			rc = ptep_force_prot(parent->mm, paddr, ptep, prot,
+			rc = ptep_force_prot(parent->mm, paddr, ptep, PROT_READ,
 					     PGSTE_VSIE_BIT);
 			if (!rc)
 				gmap_insert_rmap(sg, vmaddr, rmap);

@@ -1070,7 +1069,7 @@ static int gmap_protect_rmap(struct gmap *sg, unsigned long raddr,
 		radix_tree_preload_end();
 		if (rc) {
 			kfree(rmap);
-			rc = gmap_pte_op_fixup(parent, paddr, vmaddr, prot);
+			rc = gmap_pte_op_fixup(parent, paddr, vmaddr, PROT_READ);
 			if (rc)
 				return rc;
 			continue;

@@ -1609,7 +1608,7 @@ int gmap_shadow_r2t(struct gmap *sg, unsigned long saddr, unsigned long r2t,
 	origin = r2t & _REGION_ENTRY_ORIGIN;
 	offset = ((r2t & _REGION_ENTRY_OFFSET) >> 6) * PAGE_SIZE;
 	len = ((r2t & _REGION_ENTRY_LENGTH) + 1) * PAGE_SIZE - offset;
-	rc = gmap_protect_rmap(sg, raddr, origin + offset, len, PROT_READ);
+	rc = gmap_protect_rmap(sg, raddr, origin + offset, len);
 	spin_lock(&sg->guest_table_lock);
 	if (!rc) {
 		table = gmap_table_walk(sg, saddr, 4);

@@ -1692,7 +1691,7 @@ int gmap_shadow_r3t(struct gmap *sg, unsigned long saddr, unsigned long r3t,
 	origin = r3t & _REGION_ENTRY_ORIGIN;
 	offset = ((r3t & _REGION_ENTRY_OFFSET) >> 6) * PAGE_SIZE;
 	len = ((r3t & _REGION_ENTRY_LENGTH) + 1) * PAGE_SIZE - offset;
-	rc = gmap_protect_rmap(sg, raddr, origin + offset, len, PROT_READ);
+	rc = gmap_protect_rmap(sg, raddr, origin + offset, len);
 	spin_lock(&sg->guest_table_lock);
 	if (!rc) {
 		table = gmap_table_walk(sg, saddr, 3);

@@ -1776,7 +1775,7 @@ int gmap_shadow_sgt(struct gmap *sg, unsigned long saddr, unsigned long sgt,
 	origin = sgt & _REGION_ENTRY_ORIGIN;
 	offset = ((sgt & _REGION_ENTRY_OFFSET) >> 6) * PAGE_SIZE;
 	len = ((sgt & _REGION_ENTRY_LENGTH) + 1) * PAGE_SIZE - offset;
-	rc = gmap_protect_rmap(sg, raddr, origin + offset, len, PROT_READ);
+	rc = gmap_protect_rmap(sg, raddr, origin + offset, len);
 	spin_lock(&sg->guest_table_lock);
 	if (!rc) {
 		table = gmap_table_walk(sg, saddr, 2);

@@ -1895,7 +1894,7 @@ int gmap_shadow_pgt(struct gmap *sg, unsigned long saddr, unsigned long pgt,
 	/* Make pgt read-only in parent gmap page table (not the pgste) */
 	raddr = (saddr & _SEGMENT_MASK) | _SHADOW_RMAP_SEGMENT;
 	origin = pgt & _SEGMENT_ENTRY_ORIGIN & PAGE_MASK;
-	rc = gmap_protect_rmap(sg, raddr, origin, PAGE_SIZE, PROT_READ);
+	rc = gmap_protect_rmap(sg, raddr, origin, PAGE_SIZE);
 	spin_lock(&sg->guest_table_lock);
 	if (!rc) {
 		table = gmap_table_walk(sg, saddr, 1);

Signature · 1 line

2.14.3

Janosch Frank

Reviewed-by on v1 1/1

2018-01-24 11:55 UTC #1 lore raw

Quoted 7 lines · David Hildenbrand

We never call it with anything but PROT_READ. This is a left over from an old prototype. For creation of shadow page tables, we always only have to protect the original table in guest memory from write accesses, so we can properly invalidate the shadow on writes. Other protections are not needed.
Signed-off-by David Hildenbrand <[email protected]>

I'm not completely convinced that this is necessary, but it looks right nevertheless:

Reviewed-by Janosch Frank <[email protected]>

Quoted 84 lines

---
 arch/s390/mm/gmap.c | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

arch/s390/mm/gmap.c +8 -9

index 54cfd51a5a27..a7e05c5dea70 100644
@@ -1021,18 +1021,17 @@ static inline void gmap_insert_rmap(struct gmap *sg, unsigned long vmaddr,
 }
 
 /**
- * gmap_protect_rmap - modify access rights to memory and create an rmap
+ * gmap_protect_rmap - restrict access rights to memory (RO) and create an rmap
  * @sg: pointer to the shadow guest address space structure
  * @raddr: rmap address in the shadow gmap
  * @paddr: address in the parent guest address space
  * @len: length of the memory area to protect
- * @prot: indicates access rights: none, read-only or read-write
  *
  * Returns 0 if successfully protected and the rmap was created, -ENOMEM
  * if out of memory and -EFAULT if paddr is invalid.
  */
 static int gmap_protect_rmap(struct gmap *sg, unsigned long raddr,
-			     unsigned long paddr, unsigned long len, int prot)
+			     unsigned long paddr, unsigned long len)
 {
 	struct gmap *parent;
 	struct gmap_rmap *rmap;

@@ -1060,7 +1059,7 @@ static int gmap_protect_rmap(struct gmap *sg, unsigned long raddr,
 		ptep = gmap_pte_op_walk(parent, paddr, &ptl);
 		if (ptep) {
 			spin_lock(&sg->guest_table_lock);
-			rc = ptep_force_prot(parent->mm, paddr, ptep, prot,
+			rc = ptep_force_prot(parent->mm, paddr, ptep, PROT_READ,
 					     PGSTE_VSIE_BIT);
 			if (!rc)
 				gmap_insert_rmap(sg, vmaddr, rmap);

@@ -1070,7 +1069,7 @@ static int gmap_protect_rmap(struct gmap *sg, unsigned long raddr,
 		radix_tree_preload_end();
 		if (rc) {
 			kfree(rmap);
-			rc = gmap_pte_op_fixup(parent, paddr, vmaddr, prot);
+			rc = gmap_pte_op_fixup(parent, paddr, vmaddr, PROT_READ);
 			if (rc)
 				return rc;
 			continue;

@@ -1609,7 +1608,7 @@ int gmap_shadow_r2t(struct gmap *sg, unsigned long saddr, unsigned long r2t,
 	origin = r2t & _REGION_ENTRY_ORIGIN;
 	offset = ((r2t & _REGION_ENTRY_OFFSET) >> 6) * PAGE_SIZE;
 	len = ((r2t & _REGION_ENTRY_LENGTH) + 1) * PAGE_SIZE - offset;
-	rc = gmap_protect_rmap(sg, raddr, origin + offset, len, PROT_READ);
+	rc = gmap_protect_rmap(sg, raddr, origin + offset, len);
 	spin_lock(&sg->guest_table_lock);
 	if (!rc) {
 		table = gmap_table_walk(sg, saddr, 4);

@@ -1692,7 +1691,7 @@ int gmap_shadow_r3t(struct gmap *sg, unsigned long saddr, unsigned long r3t,
 	origin = r3t & _REGION_ENTRY_ORIGIN;
 	offset = ((r3t & _REGION_ENTRY_OFFSET) >> 6) * PAGE_SIZE;
 	len = ((r3t & _REGION_ENTRY_LENGTH) + 1) * PAGE_SIZE - offset;
-	rc = gmap_protect_rmap(sg, raddr, origin + offset, len, PROT_READ);
+	rc = gmap_protect_rmap(sg, raddr, origin + offset, len);
 	spin_lock(&sg->guest_table_lock);
 	if (!rc) {
 		table = gmap_table_walk(sg, saddr, 3);

@@ -1776,7 +1775,7 @@ int gmap_shadow_sgt(struct gmap *sg, unsigned long saddr, unsigned long sgt,
 	origin = sgt & _REGION_ENTRY_ORIGIN;
 	offset = ((sgt & _REGION_ENTRY_OFFSET) >> 6) * PAGE_SIZE;
 	len = ((sgt & _REGION_ENTRY_LENGTH) + 1) * PAGE_SIZE - offset;
-	rc = gmap_protect_rmap(sg, raddr, origin + offset, len, PROT_READ);
+	rc = gmap_protect_rmap(sg, raddr, origin + offset, len);
 	spin_lock(&sg->guest_table_lock);
 	if (!rc) {
 		table = gmap_table_walk(sg, saddr, 2);

@@ -1895,7 +1894,7 @@ int gmap_shadow_pgt(struct gmap *sg, unsigned long saddr, unsigned long pgt,
 	/* Make pgt read-only in parent gmap page table (not the pgste) */
 	raddr = (saddr & _SEGMENT_MASK) | _SHADOW_RMAP_SEGMENT;
 	origin = pgt & _SEGMENT_ENTRY_ORIGIN & PAGE_MASK;
-	rc = gmap_protect_rmap(sg, raddr, origin, PAGE_SIZE, PROT_READ);
+	rc = gmap_protect_rmap(sg, raddr, origin, PAGE_SIZE);
 	spin_lock(&sg->guest_table_lock);
 	if (!rc) {
 		table = gmap_table_walk(sg, saddr, 1);

Christian Borntraeger

Applied

2018-01-24 13:07 UTC #2 lore raw

In reply to David Hildenbrand

Thanks applied.
Martin, I will take that via the kvm tree as well.

Quoted 91 lines · David Hildenbrand

Signed-off-by David Hildenbrand <[email protected]>

---
 arch/s390/mm/gmap.c | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

arch/s390/mm/gmap.c +8 -9

index 54cfd51a5a27..a7e05c5dea70 100644
@@ -1021,18 +1021,17 @@ static inline void gmap_insert_rmap(struct gmap *sg, unsigned long vmaddr,
 }
 
 /**
- * gmap_protect_rmap - modify access rights to memory and create an rmap
+ * gmap_protect_rmap - restrict access rights to memory (RO) and create an rmap
  * @sg: pointer to the shadow guest address space structure
  * @raddr: rmap address in the shadow gmap
  * @paddr: address in the parent guest address space
  * @len: length of the memory area to protect
- * @prot: indicates access rights: none, read-only or read-write
  *
  * Returns 0 if successfully protected and the rmap was created, -ENOMEM
  * if out of memory and -EFAULT if paddr is invalid.
  */
 static int gmap_protect_rmap(struct gmap *sg, unsigned long raddr,
-			     unsigned long paddr, unsigned long len, int prot)
+			     unsigned long paddr, unsigned long len)
 {
 	struct gmap *parent;
 	struct gmap_rmap *rmap;

@@ -1060,7 +1059,7 @@ static int gmap_protect_rmap(struct gmap *sg, unsigned long raddr,
 		ptep = gmap_pte_op_walk(parent, paddr, &ptl);
 		if (ptep) {
 			spin_lock(&sg->guest_table_lock);
-			rc = ptep_force_prot(parent->mm, paddr, ptep, prot,
+			rc = ptep_force_prot(parent->mm, paddr, ptep, PROT_READ,
 					     PGSTE_VSIE_BIT);
 			if (!rc)
 				gmap_insert_rmap(sg, vmaddr, rmap);

@@ -1070,7 +1069,7 @@ static int gmap_protect_rmap(struct gmap *sg, unsigned long raddr,
 		radix_tree_preload_end();
 		if (rc) {
 			kfree(rmap);
-			rc = gmap_pte_op_fixup(parent, paddr, vmaddr, prot);
+			rc = gmap_pte_op_fixup(parent, paddr, vmaddr, PROT_READ);
 			if (rc)
 				return rc;
 			continue;

@@ -1609,7 +1608,7 @@ int gmap_shadow_r2t(struct gmap *sg, unsigned long saddr, unsigned long r2t,
 	origin = r2t & _REGION_ENTRY_ORIGIN;
 	offset = ((r2t & _REGION_ENTRY_OFFSET) >> 6) * PAGE_SIZE;
 	len = ((r2t & _REGION_ENTRY_LENGTH) + 1) * PAGE_SIZE - offset;
-	rc = gmap_protect_rmap(sg, raddr, origin + offset, len, PROT_READ);
+	rc = gmap_protect_rmap(sg, raddr, origin + offset, len);
 	spin_lock(&sg->guest_table_lock);
 	if (!rc) {
 		table = gmap_table_walk(sg, saddr, 4);

@@ -1692,7 +1691,7 @@ int gmap_shadow_r3t(struct gmap *sg, unsigned long saddr, unsigned long r3t,
 	origin = r3t & _REGION_ENTRY_ORIGIN;
 	offset = ((r3t & _REGION_ENTRY_OFFSET) >> 6) * PAGE_SIZE;
 	len = ((r3t & _REGION_ENTRY_LENGTH) + 1) * PAGE_SIZE - offset;
-	rc = gmap_protect_rmap(sg, raddr, origin + offset, len, PROT_READ);
+	rc = gmap_protect_rmap(sg, raddr, origin + offset, len);
 	spin_lock(&sg->guest_table_lock);
 	if (!rc) {
 		table = gmap_table_walk(sg, saddr, 3);

@@ -1776,7 +1775,7 @@ int gmap_shadow_sgt(struct gmap *sg, unsigned long saddr, unsigned long sgt,
 	origin = sgt & _REGION_ENTRY_ORIGIN;
 	offset = ((sgt & _REGION_ENTRY_OFFSET) >> 6) * PAGE_SIZE;
 	len = ((sgt & _REGION_ENTRY_LENGTH) + 1) * PAGE_SIZE - offset;
-	rc = gmap_protect_rmap(sg, raddr, origin + offset, len, PROT_READ);
+	rc = gmap_protect_rmap(sg, raddr, origin + offset, len);
 	spin_lock(&sg->guest_table_lock);
 	if (!rc) {
 		table = gmap_table_walk(sg, saddr, 2);

@@ -1895,7 +1894,7 @@ int gmap_shadow_pgt(struct gmap *sg, unsigned long saddr, unsigned long pgt,
 	/* Make pgt read-only in parent gmap page table (not the pgste) */
 	raddr = (saddr & _SEGMENT_MASK) | _SHADOW_RMAP_SEGMENT;
 	origin = pgt & _SEGMENT_ENTRY_ORIGIN & PAGE_MASK;
-	rc = gmap_protect_rmap(sg, raddr, origin, PAGE_SIZE, PROT_READ);
+	rc = gmap_protect_rmap(sg, raddr, origin, PAGE_SIZE);
 	spin_lock(&sg->guest_table_lock);
 	if (!rc) {
 		table = gmap_table_walk(sg, saddr, 1);