Re: [PATCH v2 2/2] iommu/iova: Free global iova rcache on iova alloc failure

[Vijayanand Jitta]

On 9/18/2020 8:11 PM, Robin Murphy wrote:
> On 2020-08-20 13:49, vjitta@xxxxxxxxxxxxxx wrote:
>> From: Vijayanand Jitta <vjitta@xxxxxxxxxxxxxx>
>>
>> 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.
>>
>> Signed-off-by: Vijayanand Jitta <vjitta@xxxxxxxxxxxxxx>
>> ---
>>   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)
> 
> As John pointed out last time, this should be static and the header
> changes dropped.
> 
> (TBH we should probably register our own hotplug notifier instance for a
> flush queue, so that external code has no need to poke at the per-CPU
> caches either)
> 
> Robin.
> 

Right, I have made it static and dropped header changes in v3.
can you please review that.

Thanks,
Vijay
>> +{
>> +    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@xxxxxxxxx>");
>>   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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