[PATCH 1/2] iommu/iova: Retry from last rb tree node if iova search fails

[PATCH 1/2] iommu/iova: Retry from last rb tree node if iova search fails

[vjitta]

From: Vijayanand Jitta <vjitta@codeaurora.org>

When ever a new iova alloc request comes iova is always searched
from the cached node and the nodes which are previous to cached
node. So, even if there is free iova space available in the nodes
which are next to the cached node iova allocation can still fail
because of this approach.

Consider the following sequence of iova alloc and frees on
1GB of iova space

1) alloc - 500MB
2) alloc - 12MB
3) alloc - 499MB
4) free -  12MB which was allocated in step 2
5) alloc - 13MB

After the above sequence we will have 12MB of free iova space and
cached node will be pointing to the iova pfn of last alloc of 13MB
which will be the lowest iova pfn of that iova space. Now if we get an
alloc request of 2MB we just search from cached node and then look
for lower iova pfn's for free iova and as they aren't any, iova alloc
fails though there is 12MB of free iova space.

To avoid such iova search failures do a retry from the last rb tree node
when iova search fails, this will search the entire tree and get an iova
if its available.

Signed-off-by: Vijayanand Jitta <vjitta@codeaurora.org>
---
 drivers/iommu/iova.c | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index 49fc01f..4e77116 100644
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -184,8 +184,9 @@ static int __alloc_and_insert_iova_range(struct iova_domain *iovad,
 	struct rb_node *curr, *prev;
 	struct iova *curr_iova;
 	unsigned long flags;
-	unsigned long new_pfn;
+	unsigned long new_pfn, low_pfn_new;
 	unsigned long align_mask = ~0UL;
+	unsigned long high_pfn = limit_pfn, low_pfn = iovad->start_pfn;
 
 	if (size_aligned)
 		align_mask <<= fls_long(size - 1);
@@ -198,15 +199,25 @@ static int __alloc_and_insert_iova_range(struct iova_domain *iovad,
 
 	curr = __get_cached_rbnode(iovad, limit_pfn);
 	curr_iova = rb_entry(curr, struct iova, node);
+	low_pfn_new = curr_iova->pfn_hi + 1;
+
+retry:
 	do {
-		limit_pfn = min(limit_pfn, curr_iova->pfn_lo);
-		new_pfn = (limit_pfn - size) & align_mask;
+		high_pfn = min(high_pfn, curr_iova->pfn_lo);
+		new_pfn = (high_pfn - size) & align_mask;
 		prev = curr;
 		curr = rb_prev(curr);
 		curr_iova = rb_entry(curr, struct iova, node);
-	} while (curr && new_pfn <= curr_iova->pfn_hi);
-
-	if (limit_pfn < size || new_pfn < iovad->start_pfn) {
+	} while (curr && new_pfn <= curr_iova->pfn_hi && new_pfn >= low_pfn);
+
+	if (high_pfn < size || new_pfn < low_pfn) {
+		if (low_pfn == iovad->start_pfn && low_pfn_new < limit_pfn) {
+			high_pfn = limit_pfn;
+			low_pfn = low_pfn_new;
+			curr = &iovad->anchor.node;
+			curr_iova = rb_entry(curr, struct iova, node);
+			goto retry;
+		}
 		iovad->max32_alloc_size = size;
 		goto iova32_full;
 	}
-- 
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[PATCH 2/2] iommu/iova: Free global iova rcache on iova alloc failure

[vjitta]

From: Vijayanand Jitta <vjitta@codeaurora.org>

When ever an iova alloc request fails we free the iova
ranges present in the percpu iova rcaches and then retry
but the global iova rcache is not freed as a result we could
still see iova alloc failure even after retry as global
rcache is holding the iova's which can cause fragmentation.
So, free the global iova rcache as well and then go for the
retry.

Change-Id: Ib8236dc88ba5516b73d4fbf6bf8e68bbf09bbad2
Signed-off-by: Vijayanand Jitta <vjitta@codeaurora.org>
---
 drivers/iommu/iova.c | 23 +++++++++++++++++++++++
 include/linux/iova.h |  6 ++++++
 2 files changed, 29 insertions(+)

diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index 4e77116..5836c87 100644
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -442,6 +442,7 @@ struct iova *find_iova(struct iova_domain *iovad, unsigned long pfn)
 		flush_rcache = false;
 		for_each_online_cpu(cpu)
 			free_cpu_cached_iovas(cpu, iovad);
+		free_global_cached_iovas(iovad);
 		goto retry;
 	}
 
@@ -1055,5 +1056,27 @@ void free_cpu_cached_iovas(unsigned int cpu, struct iova_domain *iovad)
 	}
 }
 
+/*
+ * free all the IOVA ranges of global cache
+ */
+void free_global_cached_iovas(struct iova_domain *iovad)
+{
+	struct iova_rcache *rcache;
+	unsigned long flags;
+	int i, j;
+
+	for (i = 0; i < IOVA_RANGE_CACHE_MAX_SIZE; ++i) {
+		rcache = &iovad->rcaches[i];
+		spin_lock_irqsave(&rcache->lock, flags);
+		for (j = 0; j < rcache->depot_size; ++j) {
+			iova_magazine_free_pfns(rcache->depot[j], iovad);
+			iova_magazine_free(rcache->depot[j]);
+			rcache->depot[j] = NULL;
+		}
+		rcache->depot_size = 0;
+		spin_unlock_irqrestore(&rcache->lock, flags);
+	}
+}
+
 MODULE_AUTHOR("Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>");
 MODULE_LICENSE("GPL");
diff --git a/include/linux/iova.h b/include/linux/iova.h
index a0637ab..a905726 100644
--- a/include/linux/iova.h
+++ b/include/linux/iova.h
@@ -163,6 +163,7 @@ int init_iova_flush_queue(struct iova_domain *iovad,
 struct iova *split_and_remove_iova(struct iova_domain *iovad,
 	struct iova *iova, unsigned long pfn_lo, unsigned long pfn_hi);
 void free_cpu_cached_iovas(unsigned int cpu, struct iova_domain *iovad);
+void free_global_cached_iovas(struct iova_domain *iovad);
 #else
 static inline int iova_cache_get(void)
 {
@@ -270,6 +271,11 @@ static inline void free_cpu_cached_iovas(unsigned int cpu,
 					 struct iova_domain *iovad)
 {
 }
+
+static inline void free_global_cached_iovas(struct iova_domain *iovad)
+{
+}
+
 #endif
 
 #endif
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Re: [PATCH 2/2] iommu/iova: Free global iova rcache on iova alloc failure

[Vijayanand Jitta]

On 7/3/2020 7:47 PM, vjitta@codeaurora.org wrote:
> From: Vijayanand Jitta <vjitta@codeaurora.org>
> 
> When ever an iova alloc request fails we free the iova
> ranges present in the percpu iova rcaches and then retry
> but the global iova rcache is not freed as a result we could
> still see iova alloc failure even after retry as global
> rcache is holding the iova's which can cause fragmentation.
> So, free the global iova rcache as well and then go for the
> retry.
> 
> Change-Id: Ib8236dc88ba5516b73d4fbf6bf8e68bbf09bbad2
> Signed-off-by: Vijayanand Jitta <vjitta@codeaurora.org>
> ---
>  drivers/iommu/iova.c | 23 +++++++++++++++++++++++
>  include/linux/iova.h |  6 ++++++
>  2 files changed, 29 insertions(+)
> 
> diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
> index 4e77116..5836c87 100644
> --- a/drivers/iommu/iova.c
> +++ b/drivers/iommu/iova.c
> @@ -442,6 +442,7 @@ struct iova *find_iova(struct iova_domain *iovad, unsigned long pfn)
>  		flush_rcache = false;
>  		for_each_online_cpu(cpu)
>  			free_cpu_cached_iovas(cpu, iovad);
> +		free_global_cached_iovas(iovad);
>  		goto retry;
>  	}
>  
> @@ -1055,5 +1056,27 @@ void free_cpu_cached_iovas(unsigned int cpu, struct iova_domain *iovad)
>  	}
>  }
>  
> +/*
> + * free all the IOVA ranges of global cache
> + */
> +void free_global_cached_iovas(struct iova_domain *iovad)
> +{
> +	struct iova_rcache *rcache;
> +	unsigned long flags;
> +	int i, j;
> +
> +	for (i = 0; i < IOVA_RANGE_CACHE_MAX_SIZE; ++i) {
> +		rcache = &iovad->rcaches[i];
> +		spin_lock_irqsave(&rcache->lock, flags);
> +		for (j = 0; j < rcache->depot_size; ++j) {
> +			iova_magazine_free_pfns(rcache->depot[j], iovad);
> +			iova_magazine_free(rcache->depot[j]);
> +			rcache->depot[j] = NULL;
> +		}
> +		rcache->depot_size = 0;
> +		spin_unlock_irqrestore(&rcache->lock, flags);
> +	}
> +}
> +
>  MODULE_AUTHOR("Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>");
>  MODULE_LICENSE("GPL");
> diff --git a/include/linux/iova.h b/include/linux/iova.h
> index a0637ab..a905726 100644
> --- a/include/linux/iova.h
> +++ b/include/linux/iova.h
> @@ -163,6 +163,7 @@ int init_iova_flush_queue(struct iova_domain *iovad,
>  struct iova *split_and_remove_iova(struct iova_domain *iovad,
>  	struct iova *iova, unsigned long pfn_lo, unsigned long pfn_hi);
>  void free_cpu_cached_iovas(unsigned int cpu, struct iova_domain *iovad);
> +void free_global_cached_iovas(struct iova_domain *iovad);
>  #else
>  static inline int iova_cache_get(void)
>  {
> @@ -270,6 +271,11 @@ static inline void free_cpu_cached_iovas(unsigned int cpu,
>  					 struct iova_domain *iovad)
>  {
>  }
> +
> +static inline void free_global_cached_iovas(struct iova_domain *iovad)
> +{
> +}
> +
>  #endif
>  
>  #endif
> 

ping?
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Re: [PATCH 2/2] iommu/iova: Free global iova rcache on iova alloc failure

[Joerg Roedel]

On Mon, Aug 03, 2020 at 03:30:48PM +0530, Vijayanand Jitta wrote:
> ping?

Please repost when v5.9-rc1 is released and add

	Robin Murphy <robin.murphy@arm.com>

on your Cc list.

Thanks,

	Joerg
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Re: [PATCH 2/2] iommu/iova: Free global iova rcache on iova alloc failure

[Vijayanand Jitta]

On 8/12/2020 8:46 PM, Joerg Roedel wrote:
> On Mon, Aug 03, 2020 at 03:30:48PM +0530, Vijayanand Jitta wrote:
>> ping?
> 
> Please repost when v5.9-rc1 is released and add
> 
> 	Robin Murphy <robin.murphy@arm.com>
> 
> on your Cc list.
> 
> Thanks,
> 
> 	Joerg
> 

Sure, will do.

Thanks,
Vijay
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Re: [PATCH 2/2] iommu/iova: Free global iova rcache on iova alloc failure

[John Garry]

On 13/08/2020 06:36, Vijayanand Jitta wrote:
> 
> 
> On 8/12/2020 8:46 PM, Joerg Roedel wrote:
>> On Mon, Aug 03, 2020 at 03:30:48PM +0530, Vijayanand Jitta wrote:
>>> ping?
>>
>> Please repost when v5.9-rc1 is released and add
>>
>> 	Robin Murphy <robin.murphy@arm.com>
>>
>> on your Cc list.
>>
>> Thanks,
>>
>> 	Joerg
>>
> 
> Sure, will do.
> 
> Thanks,
> Vijay
> 

And a cover letter would be useful also, to at least us know what 
changes have been made per version.

 >
 > diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
 > index 4e77116..5836c87 100644
 > --- a/drivers/iommu/iova.c
 > +++ b/drivers/iommu/iova.c
 > @@ -442,6 +442,7 @@ struct iova *find_iova(struct iova_domain *iovad, 
unsigned long pfn)
 >   		flush_rcache = false;
 >   		for_each_online_cpu(cpu)
 >   			free_cpu_cached_iovas(cpu, iovad);
 > +		free_global_cached_iovas(iovad);

Have you seen an issue where this is needed?

If we have filled the IOVA space, then as a measure we flush all the CPU 
rcaches, and then there should be free IOVA space and we can make 
progress. And it may be useful to still have the global depots to use 
straightaway then to swap into empty CPU rcaches.

 >   		goto retry;
 >   	}
 >
 > @@ -1055,5 +1056,27 @@ void free_cpu_cached_iovas(unsigned int cpu, 
struct iova_domain *iovad)
 >   	}
 >   }
 >
 > +/*
 > + * free all the IOVA ranges of global cache
 > + */
 > +void free_global_cached_iovas(struct iova_domain *iovad)
 > +{
 > +	struct iova_rcache *rcache;
 > +	unsigned long flags;
 > +	int i, j;
 > +
 > +	for (i = 0; i < IOVA_RANGE_CACHE_MAX_SIZE; ++i) {
 > +		rcache = &iovad->rcaches[i];
 > +		spin_lock_irqsave(&rcache->lock, flags);
 > +		for (j = 0; j < rcache->depot_size; ++j) {
 > +			iova_magazine_free_pfns(rcache->depot[j], iovad);
 > +			iova_magazine_free(rcache->depot[j]);
 > +			rcache->depot[j] = NULL;
 > +		}
 > +		rcache->depot_size = 0;
 > +		spin_unlock_irqrestore(&rcache->lock, flags);
 > +	}
 > +}
 > +
 >   MODULE_AUTHOR("Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>");
 >   MODULE_LICENSE("GPL");
 > diff --git a/include/linux/iova.h b/include/linux/iova.h
 > index a0637ab..a905726 100644
 > --- a/include/linux/iova.h
 > +++ b/include/linux/iova.h

why is this in the iova.h, when it is only used internally in iova.c?

 > @@ -163,6 +163,7 @@ int init_iova_flush_queue(struct iova_domain *iovad,
 >   struct iova *split_and_remove_iova(struct iova_domain *iovad,
 >   	struct iova *iova, unsigned long pfn_lo, unsigned long pfn_hi);
 >   void free_cpu_cached_iovas(unsigned int cpu, struct iova_domain 
*iovad);
 > +void free_global_cached_iovas(struct iova_domain *iovad);
 >   #else
 >   static inline int iova_cache_get(void)
 >   {
 > @@ -270,6 +271,11 @@ static inline void 
free_cpu_cached_iovas(unsigned int cpu,
 >   					 struct iova_domain *iovad)
 >   {
 >   }
 > +
 > +static inline void free_global_cached_iovas(struct iova_domain *iovad)
 > +{
 > +}
 > +
 >   #endif
 >
 >   #endif


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Re: [PATCH 1/2] iommu/iova: Retry from last rb tree node if iova search fails

[Vijayanand Jitta]

On 7/3/2020 7:47 PM, vjitta@codeaurora.org wrote:
> From: Vijayanand Jitta <vjitta@codeaurora.org>
> 
> When ever a new iova alloc request comes iova is always searched
> from the cached node and the nodes which are previous to cached
> node. So, even if there is free iova space available in the nodes
> which are next to the cached node iova allocation can still fail
> because of this approach.
> 
> Consider the following sequence of iova alloc and frees on
> 1GB of iova space
> 
> 1) alloc - 500MB
> 2) alloc - 12MB
> 3) alloc - 499MB
> 4) free -  12MB which was allocated in step 2
> 5) alloc - 13MB
> 
> After the above sequence we will have 12MB of free iova space and
> cached node will be pointing to the iova pfn of last alloc of 13MB
> which will be the lowest iova pfn of that iova space. Now if we get an
> alloc request of 2MB we just search from cached node and then look
> for lower iova pfn's for free iova and as they aren't any, iova alloc
> fails though there is 12MB of free iova space.
> 
> To avoid such iova search failures do a retry from the last rb tree node
> when iova search fails, this will search the entire tree and get an iova
> if its available.
> 
> Signed-off-by: Vijayanand Jitta <vjitta@codeaurora.org>
> ---
>  drivers/iommu/iova.c | 23 +++++++++++++++++------
>  1 file changed, 17 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
> index 49fc01f..4e77116 100644
> --- a/drivers/iommu/iova.c
> +++ b/drivers/iommu/iova.c
> @@ -184,8 +184,9 @@ static int __alloc_and_insert_iova_range(struct iova_domain *iovad,
>  	struct rb_node *curr, *prev;
>  	struct iova *curr_iova;
>  	unsigned long flags;
> -	unsigned long new_pfn;
> +	unsigned long new_pfn, low_pfn_new;
>  	unsigned long align_mask = ~0UL;
> +	unsigned long high_pfn = limit_pfn, low_pfn = iovad->start_pfn;
>  
>  	if (size_aligned)
>  		align_mask <<= fls_long(size - 1);
> @@ -198,15 +199,25 @@ static int __alloc_and_insert_iova_range(struct iova_domain *iovad,
>  
>  	curr = __get_cached_rbnode(iovad, limit_pfn);
>  	curr_iova = rb_entry(curr, struct iova, node);
> +	low_pfn_new = curr_iova->pfn_hi + 1;
> +
> +retry:
>  	do {
> -		limit_pfn = min(limit_pfn, curr_iova->pfn_lo);
> -		new_pfn = (limit_pfn - size) & align_mask;
> +		high_pfn = min(high_pfn, curr_iova->pfn_lo);
> +		new_pfn = (high_pfn - size) & align_mask;
>  		prev = curr;
>  		curr = rb_prev(curr);
>  		curr_iova = rb_entry(curr, struct iova, node);
> -	} while (curr && new_pfn <= curr_iova->pfn_hi);
> -
> -	if (limit_pfn < size || new_pfn < iovad->start_pfn) {
> +	} while (curr && new_pfn <= curr_iova->pfn_hi && new_pfn >= low_pfn);
> +
> +	if (high_pfn < size || new_pfn < low_pfn) {
> +		if (low_pfn == iovad->start_pfn && low_pfn_new < limit_pfn) {
> +			high_pfn = limit_pfn;
> +			low_pfn = low_pfn_new;
> +			curr = &iovad->anchor.node;
> +			curr_iova = rb_entry(curr, struct iova, node);
> +			goto retry;
> +		}
>  		iovad->max32_alloc_size = size;
>  		goto iova32_full;
>  	}
> 

ping?
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