Re: [issue report] pm8001 driver crashes with IOMMU enabled

[John Garry <john.garry@huawei.com>]

On 24/11/2021 12:43, Jinpu Wang wrote:
>> I notice that the driver is calling virt_to_phys() on a dma_addr_t,
>> which is broken:
> phys_to_virt you meant.

Right

>> static int pm80xx_chip_smp_req(struct pm8001_hba_info *pm8001_ha,
>> struct pm8001_ccb_info *ccb)
>> {
>> char *preq_dma_addr = NULL;
>> __le64 tmp_addr;
>>
>> tmp_addr = cpu_to_le64((u64)sg_dma_address(&task->smp_task.smp_req));
>> preq_dma_addr = (char *)phys_to_virt(tmp_addr);
>>
> The code was there since the initial support in 2013.
> f5860992db55 ("[SCSI] pm80xx: Added SPCv/ve specific hardware
> functionalities and relevant changes in common files")
> 
>> How is this supposed to work? I assume that someone has enabled the
>> IOMMU on a system with one of these cards before.

One thing to note is that a long time ago I had to fix libsas for broken 
DMA API usage which was exposed when the IOMMU enabled, which also seems 
strange not to be noticed then.

See commit 9702c67c6066 ("scsi: libsas: fix ata xfer length")

> I guess it's due to the unaligned access to memory on ARM? AFAIK most
> of the user are on x86_64.

I doubt it, especially since !IOMMU seems ok.

>> I have encountered some other RAID cards which bypasses the IOMMU to
>> access host memory - is that the case here potentially?
> I don't know, maybe guys from microchip can answer.

Hopefully.

Thanks,
John