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Correct. HW will translate GPA -> SPA automatically using below information. AMD IOMMU need special device ID to setup with GPA -> SPA mapping per VM. and its programmed in VF Control BAR (VFCntlMMIO Offset {16’b[GuestID], 6’b01_0000} Guest Miscellaneous Control Register). IOMMU HW will use this address for GPA to SPA translation for buffers like command buffer. So HW will use Base address (GPA), head/tail pointer to get the offset from Base. Then it will use GPA -> SPA translation. > > Perhaps for this reason the pinning should be done with a function > call from the driver? We still need to make sure memory allocated for page is present in memory so that IOMMU HW can access it. Pinning at the time of guest boot is enough here -OR- do we need to increase reference in queue_alloc() path ? -Vasant