Re: [RFC PATCH v2 2/5] iommu/virtio-iommu: Add probe request

[Jean-Philippe Brucker <jean-philippe.brucker@arm.com>]

On 16/01/18 23:26, Auger Eric wrote:
[...]
>> +	switch (mem->subtype) {
>> +	case VIRTIO_IOMMU_RESV_MEM_T_MSI:
>> +		region = iommu_alloc_resv_region(addr, size, prot,
>> +						 IOMMU_RESV_MSI);
> if (!region)
> 	return -ENOMEM;
>> +		break;
>> +	case VIRTIO_IOMMU_RESV_MEM_T_RESERVED:
>> +	default:
>> +		region = iommu_alloc_resv_region(addr, size, 0,
>> +						 IOMMU_RESV_RESERVED);
> same.

I'll add them, thanks

> There is another issue related to the exclusion of iovas belonging to
> reserved regions. Typically on x86, when attempting to run
> virtio-blk-pci with iommu I eventually saw the driver using iova
> belonging to the IOAPIC regions to map phys addr and this stalled qemu
> with a drown trace:
> 
> "virtio: bogus descriptor or out of resources"
> 
> those regions need to be excluded from the iova allocator. This was
> resolved by adding
> if (iommu_dma_init_domain(domain,
> 			  vdev->viommu->geometry.aperture_start,
> 			  vdev->viommu->geometry.aperture_end,
> 			  dev))
> in viommu_attach_dev()

The most recent hack for x86 [1] does call iommu_dma_init_domain() in
attach_dev(). Is it buggy?

We probably shouldn't call iommu_dma_init_domain() unconditionally
(outside of CONFIG_X86 that is), since it's normally done by the arch
(arch/arm64/mm/dma-mapping.c)

Thanks,
Jean

[1]
http://www.linux-arm.org/git?p=linux-jpb.git;a=commitdiff;h=e910e224b58712151dda06df595a53ff07edef63
on branch virtio-iommu/v0.5-x86