On 19/07/17 12:26, Anup Patel wrote: > On Wed, Jul 19, 2017 at 4:53 PM, Will Deacon <will.deacon@xxxxxxx> wrote: >> On Wed, Jul 19, 2017 at 04:49:00PM +0530, Anup Patel wrote: >>> On Wed, Jul 19, 2017 at 4:28 PM, Robin Murphy <robin.murphy@xxxxxxx> wrote: >>>> On 19/07/17 10:33, Anup Patel wrote: >>>>> Some of the IOMMUs (such as ARM SMMU) are capable of bypassing >>>>> transactions for which no IOMMU domain is configured. >>>>> >>>>> This patch adds IOMMU_CAP_BYPASS which can be used by IOMMU >>>>> drivers to advertise transation bypass capability of an IOMMU. >>>> >>>> Whatever the intended semantics of this are, I can't help thinking it >>>> would be better served by allowing callers to explicitly allocate their >>>> own IOMMU_DOMAIN_IDENTITY domains. That would also be useful for the >>>> problem we have with legacy virtio devices behind real IOMMUs. >>> >>> We want to use VFIO no-IOMMU mode for FlexRM device but >>> currently it does not allow on our SOC because IOMMU ops are >>> registered for platform bus. >> >> Why do you want to use no-IOMMU mode if you have an IOMMU, and why you do >> think the individual IOMMU drivers are the place to implement this? >> >> NAK to the SMMU patches, for the reasons outlined by Robin. > > We have limited number of SMRs on our SOC. > > There are lot of devices for which we can potentially > configure SMMU but then due to limited number of > SMRs so we use SMMU only for certain devices. Is the stream ID allocation so whacked out that you can't use masking? Robin. > For FlexRM device on our SOC, we don't intend to > use SMMU hence we need VFIO no-IOMMU mode > working for FlexRM device on our SOC. > > Please re-consider your NAK. > > Regards, > Anup >
