Re: [PATCH v7 07/12] dma-mapping: introduce dma_has_iommu()

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Sat, Oct 7, 2017 at 4:08 AM, David Woodhouse <dwmw2@xxxxxxxxxxxxx> wrote:
> On Fri, 2017-10-06 at 16:15 -0700, Dan Williams wrote:
>>
>> Right, crossed mails. The semantic I want is that the IOVA is
>> invalidated / starts throwing errors to the device because the address
>> it thought it was talking to has been remapped in the file. Once
>> userspace wakes up and responds to this invalidation event it can do
>> the actual unmap to make the IOVA reusable again.
>
> So basically you want to unmap it by removing it from the page tables
> and flushing the IOTLB, but you want the IOVA to still be reserved.
>
> The normal device-facing DMA API doesn't give you that today. You could
> do it with the IOMMU API though — that one does let you manage the IOVA
> space yourself. You don't want that IOVA used again? Well don't use it
> as the IOVA in a subsequent iommu_map() call then :)

Ah, nice. So I think I'll just add a dma_get_iommu_domain() so the
dma_ops implementation can exclude identity-mapped devices, and then
iommu_unmap() does the rest. Thanks for the pointer.




[Index of Archives]     [Linux Ext4 Filesystem]     [Union Filesystem]     [Filesystem Testing]     [Ceph Users]     [Ecryptfs]     [AutoFS]     [Kernel Newbies]     [Share Photos]     [Security]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux Cachefs]     [Reiser Filesystem]     [Linux RAID]     [Samba]     [Device Mapper]     [CEPH Development]
  Powered by Linux