Re: [PATCH 4/4] iommu/io-pgtable-arm: Prepare for TTBR1 usage

[Robin Murphy <robin.murphy@arm.com>]

On 19/08/2019 23:34, Jordan Crouse wrote:
> On Mon, Aug 19, 2019 at 07:19:31PM +0100, Robin Murphy wrote:
>> Now that callers are free to use a given table for TTBR1 if they wish
>> (all they need do is shift the provided attributes when constructing
>> their final TCR value), the only remaining impediment is the address
>> validation on map/unmap. The fact that the LPAE address space split is
>> symmetric makes this easy to accommodate - by simplifying the current
>> range checks into explicit tests that address bits above IAS are all
>> zero, it then follows straightforwardly to add the inverse test to
>> allow the all-ones case as well.
>>
>> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
>> ---
>>   drivers/iommu/io-pgtable-arm.c | 7 ++++---
>>   1 file changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
>> index 09cb20671fbb..f39c50356351 100644
>> --- a/drivers/iommu/io-pgtable-arm.c
>> +++ b/drivers/iommu/io-pgtable-arm.c
>> @@ -475,13 +475,13 @@ static int arm_lpae_map(struct io_pgtable_ops *ops, unsigned long iova,
>>   	arm_lpae_iopte *ptep = data->pgd;
>>   	int ret, lvl = ARM_LPAE_START_LVL(data);
>>   	arm_lpae_iopte prot;
>> +	long iaext = (long)iova >> data->iop.cfg.ias;
>>   
>>   	/* If no access, then nothing to do */
>>   	if (!(iommu_prot & (IOMMU_READ | IOMMU_WRITE)))
>>   		return 0;
>>   
>> -	if (WARN_ON(iova >= (1ULL << data->iop.cfg.ias) ||
>> -		    paddr >= (1ULL << data->iop.cfg.oas)))
>> +	if (WARN_ON((iaext && ~iaext) || paddr >> data->iop.cfg.oas))
>>   		return -ERANGE;
>>   
>>   	prot = arm_lpae_prot_to_pte(data, iommu_prot);
> 
> We'll want to cast away the sign extended bits before mapping the iova, this
> might be a good patch for that too as long as we are calculating the iaext.

Ah good point, I'd forgotten that ARM_LPAE_LVL_IDX() doesn't actually 
cap to IAS if the top level is smaller than bits_per_level (I suppose we 
*could* make it do so for purity, but that's bound to hurt efficiency 
far more than just zeroing out the offending bits here).

Thanks,
Robin.

> 
>> @@ -647,8 +647,9 @@ static size_t arm_lpae_unmap(struct io_pgtable_ops *ops, unsigned long iova,
>>   	struct arm_lpae_io_pgtable *data = io_pgtable_ops_to_data(ops);
>>   	arm_lpae_iopte *ptep = data->pgd;
>>   	int lvl = ARM_LPAE_START_LVL(data);
>> +	long iaext = (long)iova >> data->iop.cfg.ias;
>>   
>> -	if (WARN_ON(iova >= (1ULL << data->iop.cfg.ias)))
>> +	if (WARN_ON(iaext && ~iaext))
>>   		return 0;
>>   
>>   	return __arm_lpae_unmap(data, iova, size, lvl, ptep);
> 
> And here too.
> 
> Jordan
> 
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