[PATCH kernel 1/2] powerpc/pseries/dma: Allow swiotlb

[Thiago Jung Bauermann]

Alexey Kardashevskiy <aik at ozlabs.ru> writes:

> On 11/05/2019 08:36, Thiago Jung Bauermann wrote:
>>
>> Alexey Kardashevskiy <aik at ozlabs.ru> writes:
>>
>>> The commit 8617a5c5bc00 ("powerpc/dma: handle iommu bypass in
>>> dma_iommu_ops") merged direct DMA ops into the IOMMU DMA ops allowing
>>> SWIOTLB as well but only for mapping; the unmapping and bouncing parts
>>> were left unmodified.
>>>
>>> This adds missing direct unmapping calls to .unmap_page() and .unmap_sg().
>>>
>>> This adds missing sync callbacks and directs them to the direct DMA hooks.
>>>
>>> Fixes: 8617a5c5bc00 (powerpc/dma: handle iommu bypass in dma_iommu_ops)
>>> Signed-off-by: Alexey Kardashevskiy <aik at ozlabs.ru>
>>
>> Nice! Thanks for working on this. I have the patch at the end of this
>> email to get virtio-scsi-pci and virtio-blk-pci working in a secure
>> guest.
>
> I saw the set_pci_dma_ops(NULL) patch but could not figure out how pass
> NULL there sets the DMA ops to direct.

That causes pcibios_setup_device() to call set_dma_ops(&dev->dev, NULL),
which in turn causes dma_is_direct(get_dma_ops(dev)) to return true.

>> I applied your patch and reverted my patch and unfortunately the guest
>> hangs right after mounting the disk:
>
> Have you applied it on upstream kernel? I cannot see how it affects
> current guests as it is...

I applied it on a branch containing both Claudio Carvalho's "kvmppc:
Paravirtualize KVM to support ultravisor" series as well as my "Secure
Virtual Machine Enablement" patch series.

https://lore.kernel.org/linuxppc-dev/20190518142524.28528-1-cclaudio@linux.ibm.com/
https://lore.kernel.org/linuxppc-dev/20190521044912.1375-1-bauerman@linux.ibm.com/

--
Thiago Jung Bauermann
IBM Linux Technology Center