Re: [PATCH v3 04/18] vfio: powerpc: Move locked_vm accounting to a helper

[Alexey Kardashevskiy]

On 07/28/2014 10:46 AM, Benjamin Herrenschmidt wrote:
> On Thu, 2014-07-24 at 18:47 +1000, Alexey Kardashevskiy wrote:
>> Additional DMA windows support is coming and accounting will include them
>> so let's move this code to a helper for reuse.
> 
> This code looks a LOT like the one you added in the previous patch
> (ie. kvmppc_account_memlimit()), though in a different place. I
> wonder if we should re-arrange things so that there is really
> only one version of it..


One copy is in VFIO driver, another in KVM, they meet in VFIO KVM device
(which may miss) or IOMMU code (drivers/iommu/iommu.c or
arch/powerpc/kernel/iommu.c) but this math has nothing to do with IOMMU. I
fail to see good common place for this.


> 
>> Signed-off-by: Alexey Kardashevskiy <a...@ozlabs.ru>
>> ---
>>  drivers/vfio/vfio_iommu_spapr_tce.c | 54 
>> ++++++++++++++++++++++++-------------
>>  1 file changed, 36 insertions(+), 18 deletions(-)
>>
>> diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c 
>> b/drivers/vfio/vfio_iommu_spapr_tce.c
>> index a84788b..c8f7284 100644
>> --- a/drivers/vfio/vfio_iommu_spapr_tce.c
>> +++ b/drivers/vfio/vfio_iommu_spapr_tce.c
>> @@ -47,10 +47,40 @@ struct tce_container {
>>      bool enabled;
>>  };
>>  
>> +/*
>> + * Checks ulimit in order not to let the user space to pin all
>> + * available memory for TCE tables.
>> + */
>> +static long tce_iommu_account_memlimit(struct iommu_table *tbl, bool inc)
>> +{
>> +    unsigned long ret = 0, locked, lock_limit;
>> +    long npages;
>> +
>> +    if (!current->mm)
>> +            return -ESRCH; /* process exited */
>> +
>> +    npages = (tbl->it_size << IOMMU_PAGE_SHIFT_4K) >> PAGE_SHIFT;
>> +    if (!inc)
>> +            npages = -npages;
>> +
>> +    down_write(&current->mm->mmap_sem);
>> +    locked = current->mm->locked_vm + npages;
>> +    lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
>> +    if (locked > lock_limit && !capable(CAP_IPC_LOCK)) {
>> +            pr_warn("RLIMIT_MEMLOCK (%ld) exceeded\n",
>> +                            rlimit(RLIMIT_MEMLOCK));
>> +            ret = -ENOMEM;
>> +    } else {
>> +            current->mm->locked_vm += npages;
>> +    }
>> +    up_write(&current->mm->mmap_sem);
>> +
>> +    return ret;
>> +}
>> +
>>  static int tce_iommu_enable(struct tce_container *container)
>>  {
>>      int ret = 0;
>> -    unsigned long locked, lock_limit, npages;
>>      struct iommu_table *tbl = container->tbl;
>>  
>>      if (!container->tbl)
>> @@ -80,20 +110,11 @@ static int tce_iommu_enable(struct tce_container 
>> *container)
>>       * that would effectively kill the guest at random points, much better
>>       * enforcing the limit based on the max that the guest can map.
>>       */
>> -    down_write(&current->mm->mmap_sem);
>> -    npages = (tbl->it_size << IOMMU_PAGE_SHIFT_4K) >> PAGE_SHIFT;
>> -    locked = current->mm->locked_vm + npages;
>> -    lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
>> -    if (locked > lock_limit && !capable(CAP_IPC_LOCK)) {
>> -            pr_warn("RLIMIT_MEMLOCK (%ld) exceeded\n",
>> -                            rlimit(RLIMIT_MEMLOCK));
>> -            ret = -ENOMEM;
>> -    } else {
>> +    ret = tce_iommu_account_memlimit(tbl, true);
>> +    if (ret)
>> +            return ret;
>>  
>> -            current->mm->locked_vm += npages;
>> -            container->enabled = true;
>> -    }
>> -    up_write(&current->mm->mmap_sem);
>> +    container->enabled = true;
>>  
>>      return ret;
>>  }
>> @@ -108,10 +129,7 @@ static void tce_iommu_disable(struct tce_container 
>> *container)
>>      if (!container->tbl || !current->mm)
>>              return;
>>  
>> -    down_write(&current->mm->mmap_sem);
>> -    current->mm->locked_vm -= (container->tbl->it_size <<
>> -                    IOMMU_PAGE_SHIFT_4K) >> PAGE_SHIFT;
>> -    up_write(&current->mm->mmap_sem);
>> +    tce_iommu_account_memlimit(container->tbl, false);
>>  }
>>  
>>  static void *tce_iommu_open(unsigned long arg)
> 
> 


-- 
Alexey
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