missing clear bdr in check_ram_in_range_map()?

Posted by Baochen Qiang 1 year ago

Hi,

while checking check_ram_in_range_map() I am confused by the condition set/check on bdr.
If I am reading the code correctly, if bdr is set once, it would never get cleared, hence
that function will always returns 0.

should we clear bdr before each new iteration?

diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 5b4e6d3bf7bc..1605b956b25e 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -611,6 +611,7 @@ static int check_ram_in_range_map(unsigned long start_pfn,
                        return 1;

                start_pfn = PFN_DOWN(bdr->cpu_start) + PFN_DOWN(bdr->size);
+               bdr = NULL;
        }

        return 0;

Re: missing clear bdr in check_ram_in_range_map()?

Posted by Christoph Hellwig 1 year ago

On Mon, Dec 09, 2024 at 06:50:06PM +0800, Baochen Qiang wrote:
> Hi,
> 
> while checking check_ram_in_range_map() I am confused by the condition set/check on bdr.
> If I am reading the code correctly, if bdr is set once, it would never get cleared, hence
> that function will always returns 0.
> 
> should we clear bdr before each new iteration?

I think so.  Even better refactor the code so that the non-NULL bdr
doesn't leak out:

diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 5b4e6d3bf7bc..181e244f410a 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -584,6 +584,22 @@ int dma_direct_supported(struct device *dev, u64 mask)
 	return mask >= phys_to_dma_unencrypted(dev, min_mask);
 }
 
+static const struct bus_dma_region *dma_find_range(struct device *dev,
+		unsigned long start_pfn)
+{
+	const struct bus_dma_region *m;
+
+	for (m = dev->dma_range_map; PFN_DOWN(m->size); m++) {
+		unsigned long cpu_start_pfn = PFN_DOWN(m->cpu_start);
+
+		if (start_pfn >= cpu_start_pfn &&
+		    start_pfn - cpu_start_pfn < PFN_DOWN(m->size))
+			return m;
+	}
+
+	return NULL;
+}
+
 /*
  * To check whether all ram resource ranges are covered by dma range map
  * Returns 0 when further check is needed
@@ -593,23 +609,14 @@ static int check_ram_in_range_map(unsigned long start_pfn,
 				  unsigned long nr_pages, void *data)
 {
 	unsigned long end_pfn = start_pfn + nr_pages;
-	const struct bus_dma_region *bdr = NULL;
-	const struct bus_dma_region *m;
 	struct device *dev = data;
 
 	while (start_pfn < end_pfn) {
-		for (m = dev->dma_range_map; PFN_DOWN(m->size); m++) {
-			unsigned long cpu_start_pfn = PFN_DOWN(m->cpu_start);
+		const struct bus_dma_region *bdr;
 
-			if (start_pfn >= cpu_start_pfn &&
-			    start_pfn - cpu_start_pfn < PFN_DOWN(m->size)) {
-				bdr = m;
-				break;
-			}
-		}
+		bdr = dma_find_range(dev, start_pfn);
 		if (!bdr)
 			return 1;
-
 		start_pfn = PFN_DOWN(bdr->cpu_start) + PFN_DOWN(bdr->size);
 	}

Re: missing clear bdr in check_ram_in_range_map()?

Posted by Baochen Qiang 12 months ago


On 12/12/2024 3:14 PM, Christoph Hellwig wrote:
> On Mon, Dec 09, 2024 at 06:50:06PM +0800, Baochen Qiang wrote:
>> Hi,
>>
>> while checking check_ram_in_range_map() I am confused by the condition set/check on bdr.
>> If I am reading the code correctly, if bdr is set once, it would never get cleared, hence
>> that function will always returns 0.
>>
>> should we clear bdr before each new iteration?
> 
> I think so.  Even better refactor the code so that the non-NULL bdr
> doesn't leak out:
> 
> diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
> index 5b4e6d3bf7bc..181e244f410a 100644
> --- a/kernel/dma/direct.c
> +++ b/kernel/dma/direct.c
> @@ -584,6 +584,22 @@ int dma_direct_supported(struct device *dev, u64 mask)
>  	return mask >= phys_to_dma_unencrypted(dev, min_mask);
>  }
>  
> +static const struct bus_dma_region *dma_find_range(struct device *dev,
> +		unsigned long start_pfn)
> +{
> +	const struct bus_dma_region *m;
> +
> +	for (m = dev->dma_range_map; PFN_DOWN(m->size); m++) {
> +		unsigned long cpu_start_pfn = PFN_DOWN(m->cpu_start);
> +
> +		if (start_pfn >= cpu_start_pfn &&
> +		    start_pfn - cpu_start_pfn < PFN_DOWN(m->size))
> +			return m;
> +	}
> +
> +	return NULL;
> +}
> +
>  /*
>   * To check whether all ram resource ranges are covered by dma range map
>   * Returns 0 when further check is needed
> @@ -593,23 +609,14 @@ static int check_ram_in_range_map(unsigned long start_pfn,
>  				  unsigned long nr_pages, void *data)
>  {
>  	unsigned long end_pfn = start_pfn + nr_pages;
> -	const struct bus_dma_region *bdr = NULL;
> -	const struct bus_dma_region *m;
>  	struct device *dev = data;
>  
>  	while (start_pfn < end_pfn) {
> -		for (m = dev->dma_range_map; PFN_DOWN(m->size); m++) {
> -			unsigned long cpu_start_pfn = PFN_DOWN(m->cpu_start);
> +		const struct bus_dma_region *bdr;
>  
> -			if (start_pfn >= cpu_start_pfn &&
> -			    start_pfn - cpu_start_pfn < PFN_DOWN(m->size)) {
> -				bdr = m;
> -				break;
> -			}
> -		}
> +		bdr = dma_find_range(dev, start_pfn);
>  		if (!bdr)
>  			return 1;
> -
>  		start_pfn = PFN_DOWN(bdr->cpu_start) + PFN_DOWN(bdr->size);
>  	}
>  

looks better. thanks for reply.

Re: missing clear bdr in check_ram_in_range_map()?

Posted by Marek Szyprowski 9 months, 3 weeks ago

Hi,

On 20.12.2024 04:25, Baochen Qiang wrote:
> On 12/12/2024 3:14 PM, Christoph Hellwig wrote:
>> On Mon, Dec 09, 2024 at 06:50:06PM +0800, Baochen Qiang wrote:
>>> Hi,
>>>
>>> while checking check_ram_in_range_map() I am confused by the condition set/check on bdr.
>>> If I am reading the code correctly, if bdr is set once, it would never get cleared, hence
>>> that function will always returns 0.
>>>
>>> should we clear bdr before each new iteration?
>> I think so.  Even better refactor the code so that the non-NULL bdr
>> doesn't leak out:
>>
>> diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
>> index 5b4e6d3bf7bc..181e244f410a 100644
>> --- a/kernel/dma/direct.c
>> +++ b/kernel/dma/direct.c
>> @@ -584,6 +584,22 @@ int dma_direct_supported(struct device *dev, u64 mask)
>>   	return mask >= phys_to_dma_unencrypted(dev, min_mask);
>>   }
>>   
>> +static const struct bus_dma_region *dma_find_range(struct device *dev,
>> +		unsigned long start_pfn)
>> +{
>> +	const struct bus_dma_region *m;
>> +
>> +	for (m = dev->dma_range_map; PFN_DOWN(m->size); m++) {
>> +		unsigned long cpu_start_pfn = PFN_DOWN(m->cpu_start);
>> +
>> +		if (start_pfn >= cpu_start_pfn &&
>> +		    start_pfn - cpu_start_pfn < PFN_DOWN(m->size))
>> +			return m;
>> +	}
>> +
>> +	return NULL;
>> +}
>> +
>>   /*
>>    * To check whether all ram resource ranges are covered by dma range map
>>    * Returns 0 when further check is needed
>> @@ -593,23 +609,14 @@ static int check_ram_in_range_map(unsigned long start_pfn,
>>   				  unsigned long nr_pages, void *data)
>>   {
>>   	unsigned long end_pfn = start_pfn + nr_pages;
>> -	const struct bus_dma_region *bdr = NULL;
>> -	const struct bus_dma_region *m;
>>   	struct device *dev = data;
>>   
>>   	while (start_pfn < end_pfn) {
>> -		for (m = dev->dma_range_map; PFN_DOWN(m->size); m++) {
>> -			unsigned long cpu_start_pfn = PFN_DOWN(m->cpu_start);
>> +		const struct bus_dma_region *bdr;
>>   
>> -			if (start_pfn >= cpu_start_pfn &&
>> -			    start_pfn - cpu_start_pfn < PFN_DOWN(m->size)) {
>> -				bdr = m;
>> -				break;
>> -			}
>> -		}
>> +		bdr = dma_find_range(dev, start_pfn);
>>   		if (!bdr)
>>   			return 1;
>> -
>>   		start_pfn = PFN_DOWN(bdr->cpu_start) + PFN_DOWN(bdr->size);
>>   	}
>>   
> looks better. thanks for reply.

Could you send a formal patch with this fix, description and 
'Suggested-by: Christoph Hellwig' tag?

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland

Re: missing clear bdr in check_ram_in_range_map()?

Posted by Baochen Qiang 9 months, 2 weeks ago


On 2/28/2025 9:22 PM, Marek Szyprowski wrote:
> Hi,
> 
> On 20.12.2024 04:25, Baochen Qiang wrote:
>> On 12/12/2024 3:14 PM, Christoph Hellwig wrote:
>>> On Mon, Dec 09, 2024 at 06:50:06PM +0800, Baochen Qiang wrote:
>>>> Hi,
>>>>
>>>> while checking check_ram_in_range_map() I am confused by the condition set/check on bdr.
>>>> If I am reading the code correctly, if bdr is set once, it would never get cleared, hence
>>>> that function will always returns 0.
>>>>
>>>> should we clear bdr before each new iteration?
>>> I think so.  Even better refactor the code so that the non-NULL bdr
>>> doesn't leak out:
>>>
>>> diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
>>> index 5b4e6d3bf7bc..181e244f410a 100644
>>> --- a/kernel/dma/direct.c
>>> +++ b/kernel/dma/direct.c
>>> @@ -584,6 +584,22 @@ int dma_direct_supported(struct device *dev, u64 mask)
>>>   	return mask >= phys_to_dma_unencrypted(dev, min_mask);
>>>   }
>>>   
>>> +static const struct bus_dma_region *dma_find_range(struct device *dev,
>>> +		unsigned long start_pfn)
>>> +{
>>> +	const struct bus_dma_region *m;
>>> +
>>> +	for (m = dev->dma_range_map; PFN_DOWN(m->size); m++) {
>>> +		unsigned long cpu_start_pfn = PFN_DOWN(m->cpu_start);
>>> +
>>> +		if (start_pfn >= cpu_start_pfn &&
>>> +		    start_pfn - cpu_start_pfn < PFN_DOWN(m->size))
>>> +			return m;
>>> +	}
>>> +
>>> +	return NULL;
>>> +}
>>> +
>>>   /*
>>>    * To check whether all ram resource ranges are covered by dma range map
>>>    * Returns 0 when further check is needed
>>> @@ -593,23 +609,14 @@ static int check_ram_in_range_map(unsigned long start_pfn,
>>>   				  unsigned long nr_pages, void *data)
>>>   {
>>>   	unsigned long end_pfn = start_pfn + nr_pages;
>>> -	const struct bus_dma_region *bdr = NULL;
>>> -	const struct bus_dma_region *m;
>>>   	struct device *dev = data;
>>>   
>>>   	while (start_pfn < end_pfn) {
>>> -		for (m = dev->dma_range_map; PFN_DOWN(m->size); m++) {
>>> -			unsigned long cpu_start_pfn = PFN_DOWN(m->cpu_start);
>>> +		const struct bus_dma_region *bdr;
>>>   
>>> -			if (start_pfn >= cpu_start_pfn &&
>>> -			    start_pfn - cpu_start_pfn < PFN_DOWN(m->size)) {
>>> -				bdr = m;
>>> -				break;
>>> -			}
>>> -		}
>>> +		bdr = dma_find_range(dev, start_pfn);
>>>   		if (!bdr)
>>>   			return 1;
>>> -
>>>   		start_pfn = PFN_DOWN(bdr->cpu_start) + PFN_DOWN(bdr->size);
>>>   	}
>>>   
>> looks better. thanks for reply.
> 
> Could you send a formal patch with this fix, description and 
> 'Suggested-by: Christoph Hellwig' tag?

sure, will submit soon.

> 
> Best regards