回复: Re: [PATCH] iommu/rockchip: prevent iommus dead loop when two masters share one IOMMU

[xxm at rock-chips.com]

Hi Robin,


>On 2025-06-20 8:39 am, Simon Xue wrote:



>> When two masters share an IOMMU, calling ops->of_xlate during



>> the second master's driver init may overwrite iommu->domain set



>> by the first. This causes the check if (iommu->domain == domain)



>> in rk_iommu_attach_device() to fail, resulting in the same



>> iommu->node being added twice to &rk_domain->iommus, which can



>> lead to an infinite loop in subsequent &rk_domain->iommus operations.



>



>Indeed this is a property of the IOMMU instance itself so it really 



>should be initialised before registration, irrespective of client 



>devices. FWIW, if it's possible to take an unexpected 



>RK_MMU_IRQ_PAGE_FAULT immediately after requesting the IRQ (e.g. in a 



>kdump kernel after a crash with the hardware still running) then I think 



>the current code could probably end up dereferencing NULL in 



>report_iommu_fault() as well.


Thanks  for your review and clear explanation, I will add the information as you suggested.

Simon Xue

>



>Reviewed-by: Robin Murphy <robin.murphy at arm.com>



>



>And probably also:



>



>Cc: stable at vger.kernel.org



>Fixes: 25c2325575cc ("iommu/rockchip: Add missing set_platform_dma_ops 



>callback")



>



>Thanks,



>Robin.



>



>> Signed-off-by: Simon Xue <xxm at rock-chips.com>



>> ---



>>   drivers/iommu/rockchip-iommu.c | 3 ++-



>>   1 file changed, 2 insertions(+), 1 deletion(-)



>> 



>> diff --git a/drivers/iommu/rockchip-iommu.c b/drivers/iommu/rockchip-iommu.c



>> index 22f74ba33a0e..e6bb3c784017 100644



>> --- a/drivers/iommu/rockchip-iommu.c



>> +++ b/drivers/iommu/rockchip-iommu.c



>> @@ -1157,7 +1157,6 @@ static int rk_iommu_of_xlate(struct device *dev,



>>   		return -ENOMEM;



>>   



>>   	data->iommu = platform_get_drvdata(iommu_dev);



>> -	data->iommu->domain = &rk_identity_domain;



>>   	dev_iommu_priv_set(dev, data);



>>   



>>   	platform_device_put(iommu_dev);



>> @@ -1195,6 +1194,8 @@ static int rk_iommu_probe(struct platform_device *pdev)



>>   	if (!iommu)



>>   		return -ENOMEM;



>>   



>> +	iommu->domain = &rk_identity_domain;



>> +



>>   	platform_set_drvdata(pdev, iommu);



>>   	iommu->dev = dev;



>>   	iommu->num_mmu = 0;



>



>