[dpdk-dev] [PATCH] bus/pci: forbid VA as IOVA mode if IOMMU address width too small

Maxime Coquelin maxime.coquelin at redhat.com
Mon Jan 8 17:48:46 CET 2018



On 01/08/2018 04:54 PM, Maxime Coquelin wrote:
> 
> 
> On 01/08/2018 04:38 PM, Stephen Hemminger wrote:
>> On Mon,  8 Jan 2018 14:51:27 +0100
>> Maxime Coquelin <maxime.coquelin at redhat.com> wrote:
>>
>>> +static inline bool
>>> +pci_one_device_iommu_support_va(struct rte_pci_device *dev)
>>> +{
>>> +#if defined(RTE_ARCH_PPC_64)
>>> +    return false;
>>> +#elif defined(RTE_ARCH_X86)
>>> +
>>
>> The cleaner way to handle this kind of ifdef is:
>>
>> #ifdef RTE_ARCH_X86
>> static bool
>> pci_one_device_iommu_support_va(struct rte_pci_device *dev)
>> {
>> ....
>> }
>> #elif defined(RTE_ARCH_PPC_64)
>> static inline bool
>> pci_one_device_iommu_support_va(struct rte_pci_device *dev)
>> {
>>     return false;
>> }
>> #endif
> 
> Ok, thanks. I do this in v2.
> 
>> What about AMD64?
> 
> I haven't checked AMD64 spec yet.

 From AMD IOMMU spec (see [0], page 178), the only supported Guest
Virtual Address size is 48bits, so above the 47 bits of user VA on x86.

So in this regard, AMD IOMMU is compatible with using VA as IOVA.

Cheers,
Maxime

[0]: https://support.amd.com/TechDocs/48882_IOMMU.pdf


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