diff mbox series

[v5,05/13] KVM: Integrate gfn_to_memslot_approx() into search_memslots()

Message ID d0d2c6fda0a21962eefcf28b37a603caa4be1819.1632171479.git.maciej.szmigiero@oracle.com (mailing list archive)
State New, archived
Headers show
Series KVM: Scalable memslots implementation | expand

Commit Message

Maciej S. Szmigiero Sept. 20, 2021, 9:38 p.m. UTC 
From: "Maciej S. Szmigiero" <maciej.szmigiero@oracle.com>

s390 arch has gfn_to_memslot_approx() which is almost identical to
search_memslots(), differing only in that in case the gfn falls in a hole
one of the memslots bordering the hole is returned.

Add this lookup mode as an option to search_memslots() so we don't have two
almost identical functions for looking up a memslot by its gfn.

Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
---
 arch/s390/kvm/kvm-s390.c | 39 ++-------------------------------------
 include/linux/kvm_host.h | 25 ++++++++++++++++++++++---
 virt/kvm/kvm_main.c      |  2 +-
 3 files changed, 25 insertions(+), 41 deletions(-)

Comments

Sean Christopherson Oct. 19, 2021, 11:38 p.m. UTC | #1 
On Mon, Sep 20, 2021, Maciej S. Szmigiero wrote:
> @@ -1267,7 +1280,7 @@ search_memslots(struct kvm_memslots *slots, gfn_t gfn, int *index)
>   * itself isn't here as an inline because that would bloat other code too much.
>   */
>  static inline struct kvm_memory_slot *
> -__gfn_to_memslot(struct kvm_memslots *slots, gfn_t gfn)
> +__gfn_to_memslot_approx(struct kvm_memslots *slots, gfn_t gfn, bool approx)

This function name is a misnomer.  The helper is not an "approx" version, it's an
inner helper that takes an @approx param.  Unless someone has a more clever name,
the dreaded four underscores seems like the way to go.  Warning away users is a
good thing in this case...

>  {
>  	struct kvm_memory_slot *slot;
>  	int slot_index = atomic_read(&slots->last_used_slot);
> @@ -1276,7 +1289,7 @@ __gfn_to_memslot(struct kvm_memslots *slots, gfn_t gfn)
>  	if (slot)
>  		return slot;
>  
> -	slot = search_memslots(slots, gfn, &slot_index);
> +	slot = search_memslots(slots, gfn, &slot_index, approx);
>  	if (slot) {
>  		atomic_set(&slots->last_used_slot, slot_index);
>  		return slot;
> @@ -1285,6 +1298,12 @@ __gfn_to_memslot(struct kvm_memslots *slots, gfn_t gfn)
>  	return NULL;
>  }
>  

There's a comment that doesn't show up in this diff that should also be moved,
and opportunistically updated.

> +static inline struct kvm_memory_slot *
> +__gfn_to_memslot(struct kvm_memslots *slots, gfn_t gfn)
> +{
> +	return __gfn_to_memslot_approx(slots, gfn, false);
> +}
> +
>  static inline unsigned long
>  __gfn_to_hva_memslot(const struct kvm_memory_slot *slot, gfn_t gfn)
>  {

E.g. this as fixup?

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 540fa948baa5..2964c773b36c 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -1964,10 +1964,15 @@ static int kvm_s390_peek_cmma(struct kvm *kvm, struct kvm_s390_cmma_log *args,
        return 0;
 }

+static int gfn_to_memslot_approx(struct kvm_memslots *slots, gfn_t gfn)
+{
+       return ____gfn_to_memslot(slots, cur_gfn, true);
+}
+
 static unsigned long kvm_s390_next_dirty_cmma(struct kvm_memslots *slots,
                                              unsigned long cur_gfn)
 {
-       struct kvm_memory_slot *ms = __gfn_to_memslot_approx(slots, cur_gfn, true);
+       struct kvm_memory_slot *ms = gfn_to_memslot_approx(slots, cur_gfn);
        int slotidx = ms - slots->memslots;
        unsigned long ofs = cur_gfn - ms->base_gfn;

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 8fd9644f40b2..ec1a074c2f6e 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1274,13 +1274,8 @@ search_memslots(struct kvm_memslots *slots, gfn_t gfn, int *index, bool approx)
        return NULL;
 }

-/*
- * __gfn_to_memslot() and its descendants are here because it is called from
- * non-modular code in arch/powerpc/kvm/book3s_64_vio{,_hv}.c. gfn_to_memslot()
- * itself isn't here as an inline because that would bloat other code too much.
- */
 static inline struct kvm_memory_slot *
-__gfn_to_memslot_approx(struct kvm_memslots *slots, gfn_t gfn, bool approx)
+____gfn_to_memslot(struct kvm_memslots *slots, gfn_t gfn, bool approx)
 {
        struct kvm_memory_slot *slot;
        int slot_index = atomic_read(&slots->last_used_slot);
@@ -1298,10 +1293,15 @@ __gfn_to_memslot_approx(struct kvm_memslots *slots, gfn_t gfn, bool approx)
        return NULL;
 }

+/*
+ * __gfn_to_memslot() and its descendants are here to allow arch code to inline
+ * the lookups in hot paths.  gfn_to_memslot() itself isn't here as an inline
+ * because that would bloat other code too much.
+ */
 static inline struct kvm_memory_slot *
 __gfn_to_memslot(struct kvm_memslots *slots, gfn_t gfn)
 {
-       return __gfn_to_memslot_approx(slots, gfn, false);
+       return ____gfn_to_memslot(slots, gfn, false);
 }

 static inline unsigned long
Maciej S. Szmigiero Oct. 20, 2021, 6:41 p.m. UTC | #2 
On 20.10.2021 01:38, Sean Christopherson wrote:
> On Mon, Sep 20, 2021, Maciej S. Szmigiero wrote:
>> @@ -1267,7 +1280,7 @@ search_memslots(struct kvm_memslots *slots, gfn_t gfn, int *index)
>>    * itself isn't here as an inline because that would bloat other code too much.
>>    */
>>   static inline struct kvm_memory_slot *
>> -__gfn_to_memslot(struct kvm_memslots *slots, gfn_t gfn)
>> +__gfn_to_memslot_approx(struct kvm_memslots *slots, gfn_t gfn, bool approx)
> 
> This function name is a misnomer.  The helper is not an "approx" version, it's an
> inner helper that takes an @approx param.  Unless someone has a more clever name,
> the dreaded four underscores seems like the way to go.  Warning away users is a
> good thing in this case...
> 
>>   {
>>   	struct kvm_memory_slot *slot;
>>   	int slot_index = atomic_read(&slots->last_used_slot);
>> @@ -1276,7 +1289,7 @@ __gfn_to_memslot(struct kvm_memslots *slots, gfn_t gfn)
>>   	if (slot)
>>   		return slot;
>>   
>> -	slot = search_memslots(slots, gfn, &slot_index);
>> +	slot = search_memslots(slots, gfn, &slot_index, approx);
>>   	if (slot) {
>>   		atomic_set(&slots->last_used_slot, slot_index);
>>   		return slot;
>> @@ -1285,6 +1298,12 @@ __gfn_to_memslot(struct kvm_memslots *slots, gfn_t gfn)
>>   	return NULL;
>>   }
>>   
> 
> There's a comment that doesn't show up in this diff that should also be moved,
> and opportunistically updated.
> 
>> +static inline struct kvm_memory_slot *
>> +__gfn_to_memslot(struct kvm_memslots *slots, gfn_t gfn)
>> +{
>> +	return __gfn_to_memslot_approx(slots, gfn, false);
>> +}
>> +
>>   static inline unsigned long
>>   __gfn_to_hva_memslot(const struct kvm_memory_slot *slot, gfn_t gfn)
>>   {
> 
> E.g. this as fixup?
> 
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 540fa948baa5..2964c773b36c 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -1964,10 +1964,15 @@ static int kvm_s390_peek_cmma(struct kvm *kvm, struct kvm_s390_cmma_log *args,
>          return 0;
>   }
> 
> +static int gfn_to_memslot_approx(struct kvm_memslots *slots, gfn_t gfn)
> +{
> +       return ____gfn_to_memslot(slots, cur_gfn, true);
> +}
> +
>   static unsigned long kvm_s390_next_dirty_cmma(struct kvm_memslots *slots,
>                                                unsigned long cur_gfn)
>   {
> -       struct kvm_memory_slot *ms = __gfn_to_memslot_approx(slots, cur_gfn, true);
> +       struct kvm_memory_slot *ms = gfn_to_memslot_approx(slots, cur_gfn);
>          int slotidx = ms - slots->memslots;
>          unsigned long ofs = cur_gfn - ms->base_gfn;
> 
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 8fd9644f40b2..ec1a074c2f6e 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -1274,13 +1274,8 @@ search_memslots(struct kvm_memslots *slots, gfn_t gfn, int *index, bool approx)
>          return NULL;
>   }
> 
> -/*
> - * __gfn_to_memslot() and its descendants are here because it is called from
> - * non-modular code in arch/powerpc/kvm/book3s_64_vio{,_hv}.c. gfn_to_memslot()
> - * itself isn't here as an inline because that would bloat other code too much.
> - */
>   static inline struct kvm_memory_slot *
> -__gfn_to_memslot_approx(struct kvm_memslots *slots, gfn_t gfn, bool approx)
> +____gfn_to_memslot(struct kvm_memslots *slots, gfn_t gfn, bool approx)
>   {
>          struct kvm_memory_slot *slot;
>          int slot_index = atomic_read(&slots->last_used_slot);
> @@ -1298,10 +1293,15 @@ __gfn_to_memslot_approx(struct kvm_memslots *slots, gfn_t gfn, bool approx)
>          return NULL;
>   }
> 
> +/*
> + * __gfn_to_memslot() and its descendants are here to allow arch code to inline
> + * the lookups in hot paths.  gfn_to_memslot() itself isn't here as an inline
> + * because that would bloat other code too much.
> + */
>   static inline struct kvm_memory_slot *
>   __gfn_to_memslot(struct kvm_memslots *slots, gfn_t gfn)
>   {
> -       return __gfn_to_memslot_approx(slots, gfn, false);
> +       return ____gfn_to_memslot(slots, gfn, false);
>   }
> 
>   static inline unsigned long
> 

Looks sensible, will apply your proposed changes.

Thanks,
Maciej
diff mbox series

Patch

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 3fd0f4afe742..540fa948baa5 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -1941,41 +1941,6 @@  static long kvm_s390_set_skeys(struct kvm *kvm, struct kvm_s390_skeys *args)
 /* for consistency */
 #define KVM_S390_CMMA_SIZE_MAX ((u32)KVM_S390_SKEYS_MAX)
 
-/*
- * Similar to gfn_to_memslot, but returns the index of a memslot also when the
- * address falls in a hole. In that case the index of one of the memslots
- * bordering the hole is returned.
- */
-static int gfn_to_memslot_approx(struct kvm_memslots *slots, gfn_t gfn)
-{
-	int start = 0, end = slots->used_slots;
-	int slot = atomic_read(&slots->last_used_slot);
-	struct kvm_memory_slot *memslots = slots->memslots;
-
-	if (gfn >= memslots[slot].base_gfn &&
-	    gfn < memslots[slot].base_gfn + memslots[slot].npages)
-		return slot;
-
-	while (start < end) {
-		slot = start + (end - start) / 2;
-
-		if (gfn >= memslots[slot].base_gfn)
-			end = slot;
-		else
-			start = slot + 1;
-	}
-
-	if (start >= slots->used_slots)
-		return slots->used_slots - 1;
-
-	if (gfn >= memslots[start].base_gfn &&
-	    gfn < memslots[start].base_gfn + memslots[start].npages) {
-		atomic_set(&slots->last_used_slot, start);
-	}
-
-	return start;
-}
-
 static int kvm_s390_peek_cmma(struct kvm *kvm, struct kvm_s390_cmma_log *args,
 			      u8 *res, unsigned long bufsize)
 {
@@ -2002,8 +1967,8 @@  static int kvm_s390_peek_cmma(struct kvm *kvm, struct kvm_s390_cmma_log *args,
 static unsigned long kvm_s390_next_dirty_cmma(struct kvm_memslots *slots,
 					      unsigned long cur_gfn)
 {
-	int slotidx = gfn_to_memslot_approx(slots, cur_gfn);
-	struct kvm_memory_slot *ms = slots->memslots + slotidx;
+	struct kvm_memory_slot *ms = __gfn_to_memslot_approx(slots, cur_gfn, true);
+	int slotidx = ms - slots->memslots;
 	unsigned long ofs = cur_gfn - ms->base_gfn;
 
 	if (ms->base_gfn + ms->npages <= cur_gfn) {
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index c6963f6f1eb8..8fd9644f40b2 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1231,10 +1231,14 @@  try_get_memslot(struct kvm_memslots *slots, int slot_index, gfn_t gfn)
  * Returns a pointer to the memslot that contains gfn and records the index of
  * the slot in index. Otherwise returns NULL.
  *
+ * With "approx" set returns the memslot also when the address falls
+ * in a hole. In that case one of the memslots bordering the hole is
+ * returned.
+ *
  * IMPORTANT: Slots are sorted from highest GFN to lowest GFN!
  */
 static inline struct kvm_memory_slot *
-search_memslots(struct kvm_memslots *slots, gfn_t gfn, int *index)
+search_memslots(struct kvm_memslots *slots, gfn_t gfn, int *index, bool approx)
 {
 	int start = 0, end = slots->used_slots;
 	struct kvm_memory_slot *memslots = slots->memslots;
@@ -1252,11 +1256,20 @@  search_memslots(struct kvm_memslots *slots, gfn_t gfn, int *index)
 			start = slot + 1;
 	}
 
+	if (approx && start >= slots->used_slots) {
+		*index = slots->used_slots - 1;
+		return &memslots[slots->used_slots - 1];
+	}
+
 	slot = try_get_memslot(slots, start, gfn);
 	if (slot) {
 		*index = start;
 		return slot;
 	}
+	if (approx) {
+		*index = start;
+		return &memslots[start];
+	}
 
 	return NULL;
 }
@@ -1267,7 +1280,7 @@  search_memslots(struct kvm_memslots *slots, gfn_t gfn, int *index)
  * itself isn't here as an inline because that would bloat other code too much.
  */
 static inline struct kvm_memory_slot *
-__gfn_to_memslot(struct kvm_memslots *slots, gfn_t gfn)
+__gfn_to_memslot_approx(struct kvm_memslots *slots, gfn_t gfn, bool approx)
 {
 	struct kvm_memory_slot *slot;
 	int slot_index = atomic_read(&slots->last_used_slot);
@@ -1276,7 +1289,7 @@  __gfn_to_memslot(struct kvm_memslots *slots, gfn_t gfn)
 	if (slot)
 		return slot;
 
-	slot = search_memslots(slots, gfn, &slot_index);
+	slot = search_memslots(slots, gfn, &slot_index, approx);
 	if (slot) {
 		atomic_set(&slots->last_used_slot, slot_index);
 		return slot;
@@ -1285,6 +1298,12 @@  __gfn_to_memslot(struct kvm_memslots *slots, gfn_t gfn)
 	return NULL;
 }
 
+static inline struct kvm_memory_slot *
+__gfn_to_memslot(struct kvm_memslots *slots, gfn_t gfn)
+{
+	return __gfn_to_memslot_approx(slots, gfn, false);
+}
+
 static inline unsigned long
 __gfn_to_hva_memslot(const struct kvm_memory_slot *slot, gfn_t gfn)
 {
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index c3c71a9e85c9..14043a6edb88 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2062,7 +2062,7 @@  struct kvm_memory_slot *kvm_vcpu_gfn_to_memslot(struct kvm_vcpu *vcpu, gfn_t gfn
 	 * search_memslots() instead of __gfn_to_memslot() to avoid
 	 * thrashing the VM-wide last_used_index in kvm_memslots.
 	 */
-	slot = search_memslots(slots, gfn, &slot_index);
+	slot = search_memslots(slots, gfn, &slot_index, false);
 	if (slot) {
 		vcpu->last_used_slot = slot_index;
 		return slot;