linux-kernel - Re: [PATCH v2 2/3] s390/pci: store DMA offset in bus_dma

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Message-ID: <ddebeba2-e32c-4c00-8107-4f4e3850c477@linux.ibm.com>
Date: Mon, 16 Dec 2024 11:51:58 -0500
From: Matthew Rosato <mjrosato@...ux.ibm.com>
To: Niklas Schnelle <schnelle@...ux.ibm.com>, joro@...tes.org, will@...nel.org,
        robin.murphy@....com, gerald.schaefer@...ux.ibm.com
Cc: hca@...ux.ibm.com, gor@...ux.ibm.com, agordeev@...ux.ibm.com,
        svens@...ux.ibm.com, borntraeger@...ux.ibm.com, farman@...ux.ibm.com,
        clegoate@...hat.com, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org
Subject: Re: [PATCH v2 2/3] s390/pci: store DMA offset in bus_dma_region


>>> +	map->cpu_start = 0;
>>> +	map->dma_start = PAGE_ALIGN(zdev->start_dma);
>>> +	map->size = (u64)virt_to_phys(high_memory);
>>
>> I don't think we should restrict the size here to the size of memory.
>> Instead I think it should be zdev->end_dma - zdev->start_dma.
>>
>> Since we handle the restriction to memory size as reserved regions I
>> think that should be compatible. Also I think otherwise this might
>> break the admittedly odd s390_iommu_aperture=X kernel parameter on
>> LPARs.
> 
> Correction, zdev->end_dma - zdev->start_dma + 1 because zdev->end_dma
> is inclusive ;-)
> 

Forgot about that parameter, thanks...  OK, will change to:

map->size = zdev->end_dma - zdev->start_dma + 1;