Re: [U-Boot] [PATCH v2] bootm: Align cache flush begin address

[Simon Glass]

Hi Bryan,

On 18 April 2018 at 11:22, Bryan O'Donoghue  wrote:
>
>
>
> On 17/04/18 23:21, Simon Glass wrote:
>>
>> Hi Bryan,
>>
>> On 17 April 2018 at 03:27, Bryan O'Donoghue  
>> wrote:
>>>
>>>
>>>
>>>
>>> On 16/04/18 17:49, Simon Glass wrote:


 On 15 April 2018 at 04:48, Bryan O'Donoghue  
 wrote:
>
>
> commit b4d956f6bc0f ("bootm: Align cache flush end address correctly")
> aligns the end address of the cache flush operation to a cache-line size 
> to
> ensure lower-layers in the code accept the range provided and flush.
>
> A similar action should be taken for the begin address of a cache flush
> operation. The load address may not be aligned to a cache-line boundary, 
> so
> ensure the passed address is aligned.
>
> Signed-off-by: Bryan O'Donoghue 
> Reported-by: Breno Matheus Lima 
> Suggested-by: Tom Rini 
> Cc: Simon Glass 
> ---
>common/bootm.c | 8 +++-
>1 file changed, 7 insertions(+), 1 deletion(-)



 I feel that using an unaligned start address should probably be an
 error. Why would that be useful?

 Apart from that:

 Reviewed-by: Simon Glass 

 Regards,
 Simon

>>>
>>> We are booting a kernel that has an entry point aligned a cacheline 
>>> boundary with a header prefix/load-address that is a negative offset from 
>>> that.
>>>
>>> We could go about trying to move the load/ep address of that kernel but, my 
>>> feeling is that's probably the wrong thing to do, we can just as easily 
>>> align-down and add to the flush length.
>>
>>
>> What header is this? Perhaps it should be updated to be a cache-line
>> multiple in size?
>
>
> I don't think so it's a TEE header, that's pretty fixed.
>
>> I suspect the impact of this patch is minimal, since people hopefully
>> don't put data just before the image is loaded. But if they did, and
>> the image is loaded using DMA behind the cache, we might have tricky
>> bugs. That's why in general I'm not keen on silently messing with the
>> cache outside the expected range.
>
>
> Yes, I agree with both points.
>
> How printing a warning ?
>
> if (flush_start < load)
> flush_len += load - flush_start;
>
> if (flush_start < load) {
> printf("WARNING: unaligned load address 0x%08lx flushing 0x%08lx\n",
>load, flush_start);
>
> flush_len += load - flush_start;
> }

That seems like a good idea.

Regards,
Simon
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Re: [U-Boot] [PATCH v2] bootm: Align cache flush begin address

[Bryan O'Donoghue]

On 17/04/18 23:21, Simon Glass wrote:

Hi Bryan,

On 17 April 2018 at 03:27, Bryan O'Donoghue  wrote:




On 16/04/18 17:49, Simon Glass wrote:


On 15 April 2018 at 04:48, Bryan O'Donoghue  wrote:


commit b4d956f6bc0f ("bootm: Align cache flush end address correctly")
aligns the end address of the cache flush operation to a cache-line size to
ensure lower-layers in the code accept the range provided and flush.

A similar action should be taken for the begin address of a cache flush
operation. The load address may not be aligned to a cache-line boundary, so
ensure the passed address is aligned.

Signed-off-by: Bryan O'Donoghue 
Reported-by: Breno Matheus Lima 
Suggested-by: Tom Rini 
Cc: Simon Glass 
---
   common/bootm.c | 8 +++-
   1 file changed, 7 insertions(+), 1 deletion(-)



I feel that using an unaligned start address should probably be an
error. Why would that be useful?

Apart from that:

Reviewed-by: Simon Glass 

Regards,
Simon



We are booting a kernel that has an entry point aligned a cacheline boundary 
with a header prefix/load-address that is a negative offset from that.

We could go about trying to move the load/ep address of that kernel but, my 
feeling is that's probably the wrong thing to do, we can just as easily 
align-down and add to the flush length.


What header is this? Perhaps it should be updated to be a cache-line
multiple in size?


I don't think so it's a TEE header, that's pretty fixed.


I suspect the impact of this patch is minimal, since people hopefully
don't put data just before the image is loaded. But if they did, and
the image is loaded using DMA behind the cache, we might have tricky
bugs. That's why in general I'm not keen on silently messing with the
cache outside the expected range.


Yes, I agree with both points.

How printing a warning ?

if (flush_start < load)
flush_len += load - flush_start;

if (flush_start < load) {
printf("WARNING: unaligned load address 0x%08lx flushing 0x%08lx\n",
   load, flush_start);
flush_len += load - flush_start;
}
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Re: [U-Boot] [PATCH v2] bootm: Align cache flush begin address

[Simon Glass]

Hi Bryan,

On 17 April 2018 at 03:27, Bryan O'Donoghue  wrote:
>
>
>
> On 16/04/18 17:49, Simon Glass wrote:
>>
>> On 15 April 2018 at 04:48, Bryan O'Donoghue  
>> wrote:
>>>
>>> commit b4d956f6bc0f ("bootm: Align cache flush end address correctly")
>>> aligns the end address of the cache flush operation to a cache-line size to
>>> ensure lower-layers in the code accept the range provided and flush.
>>>
>>> A similar action should be taken for the begin address of a cache flush
>>> operation. The load address may not be aligned to a cache-line boundary, so
>>> ensure the passed address is aligned.
>>>
>>> Signed-off-by: Bryan O'Donoghue 
>>> Reported-by: Breno Matheus Lima 
>>> Suggested-by: Tom Rini 
>>> Cc: Simon Glass 
>>> ---
>>>   common/bootm.c | 8 +++-
>>>   1 file changed, 7 insertions(+), 1 deletion(-)
>>
>>
>> I feel that using an unaligned start address should probably be an
>> error. Why would that be useful?
>>
>> Apart from that:
>>
>> Reviewed-by: Simon Glass 
>>
>> Regards,
>> Simon
>>
>
> We are booting a kernel that has an entry point aligned a cacheline boundary 
> with a header prefix/load-address that is a negative offset from that.
>
> We could go about trying to move the load/ep address of that kernel but, my 
> feeling is that's probably the wrong thing to do, we can just as easily 
> align-down and add to the flush length.

What header is this? Perhaps it should be updated to be a cache-line
multiple in size?

I suspect the impact of this patch is minimal, since people hopefully
don't put data just before the image is loaded. But if they did, and
the image is loaded using DMA behind the cache, we might have tricky
bugs. That's why in general I'm not keen on silently messing with the
cache outside the expected range.

Regards,
Simon
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Re: [U-Boot] [PATCH v2] bootm: Align cache flush begin address

[Bryan O'Donoghue]

On 16/04/18 17:49, Simon Glass wrote:

On 15 April 2018 at 04:48, Bryan O'Donoghue  wrote:

commit b4d956f6bc0f ("bootm: Align cache flush end address correctly")
aligns the end address of the cache flush operation to a cache-line size to
ensure lower-layers in the code accept the range provided and flush.

A similar action should be taken for the begin address of a cache flush
operation. The load address may not be aligned to a cache-line boundary, so
ensure the passed address is aligned.

Signed-off-by: Bryan O'Donoghue 
Reported-by: Breno Matheus Lima 
Suggested-by: Tom Rini 
Cc: Simon Glass 
---
  common/bootm.c | 8 +++-
  1 file changed, 7 insertions(+), 1 deletion(-)


I feel that using an unaligned start address should probably be an
error. Why would that be useful?

Apart from that:

Reviewed-by: Simon Glass 

Regards,
Simon



We are booting a kernel that has an entry point aligned a cacheline 
boundary with a header prefix/load-address that is a negative offset 
from that.


We could go about trying to move the load/ep address of that kernel but, 
my feeling is that's probably the wrong thing to do, we can just as 
easily align-down and add to the flush length.


---
bod
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Re: [U-Boot] [PATCH v2] bootm: Align cache flush begin address

[Simon Glass]

On 15 April 2018 at 04:48, Bryan O'Donoghue  wrote:
> commit b4d956f6bc0f ("bootm: Align cache flush end address correctly")
> aligns the end address of the cache flush operation to a cache-line size to
> ensure lower-layers in the code accept the range provided and flush.
>
> A similar action should be taken for the begin address of a cache flush
> operation. The load address may not be aligned to a cache-line boundary, so
> ensure the passed address is aligned.
>
> Signed-off-by: Bryan O'Donoghue 
> Reported-by: Breno Matheus Lima 
> Suggested-by: Tom Rini 
> Cc: Simon Glass 
> ---
>  common/bootm.c | 8 +++-
>  1 file changed, 7 insertions(+), 1 deletion(-)

I feel that using an unaligned start address should probably be an
error. Why would that be useful?

Apart from that:

Reviewed-by: Simon Glass 

Regards,
Simon
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Re: [U-Boot] [PATCH v2] bootm: Align cache flush begin address

[Breno Matheus Lima]

Hi Bryan,

2018-04-15 7:48 GMT-03:00 Bryan O'Donoghue :
> commit b4d956f6bc0f ("bootm: Align cache flush end address correctly")
> aligns the end address of the cache flush operation to a cache-line size to
> ensure lower-layers in the code accept the range provided and flush.
>
> A similar action should be taken for the begin address of a cache flush
> operation. The load address may not be aligned to a cache-line boundary, so
> ensure the passed address is aligned.
>
> Signed-off-by: Bryan O'Donoghue 
> Reported-by: Breno Matheus Lima 
> Suggested-by: Tom Rini 
> Cc: Simon Glass 

Thanks for the fix, I'm not seeing the issue anymore.

Tested-by: Breno Lima 
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