Hi Eric, On Mon, 2021-09-13 at 10:19 +0200, Eric Auger wrote: > Hi Shashi, > > On 9/10/21 3:32 PM, shashi.mall...@linaro.org wrote: > > So that would be the driver code running in guest OS because i see > > tables being setup by arm-smmu driver code in linux,which is > > similar to > > what happens with ITS(table base addresses programmed in registers > > by > > linux driver). > Stage2 SMMU tables are generally not used today. Only stage 1 is > used, > even with VFIO (with KVM). The stage 2 SMMU capability is required for qemu sbsa reference platform to satisfy the sbsa level 3 acs(arm compliance suite) requirements.
> SMMUv3 upstream driver does not support S1+S2 (nested). It only > supports > either S1 or S2. Enabling S2 can be done through VFIO driver, if you > select the VFIO_TYPE1_NESTING_IOMMU IOMMU type. This then calls IOMMU > .enable_nesting = arm_smmu_enable_nesting which sets smmu_domain- > >stage > = ARM_SMMU_DOMAIN_NESTED. But the name is misleading as it actually > forces the use of S2 instead of S1. > > However if you look at QEMU VFIO code, no one uses > VFIO_TYPE1_NESTING_IOMMU. Since the current smmuv3 implementation in qemu advertises only stage 1 support,from the qemu device point of view is the stage 2 support included in the integration effort you mentioned or does it need to be taken up from scratch? > > Note I have worked on 2 stage integration for years, without much > success yet: > [RFC v9 00/29] vSMMUv3/pSMMUv3 2 stage VFIO integration > > [PATCH v15 00/12] SMMUv3 Nested Stage Setup (IOMMU part) > [PATCH v13 00/13] SMMUv3 Nested Stage Setup (VFIO part) > > > Thanks > > Eric > > On Fri, 2021-09-10 at 13:54 +0100, Peter Maydell wrote: > > > On Fri, 10 Sept 2021 at 13:39, <shashi.mall...@linaro.org> wrote: > > > > I am referring to the latter,"purely emulated QEMU with an > > > > emulated > > > > SMMU that handles accesses to emulated devices" > > > In that case, the stage 2 tables are set up by the guest > > > code (running at emulated EL2), just as they would be if > > > it were running on real hardware. > > > > > > -- PMM
