Yang Zhang <yang.zhang.wz@xxxxxxxxx> wrote: > I think it is not only interrupt. There must have the DMAR emulation and > the cost for DMA is heavy in VM(DMA operations are very frequently). I > cannot remember whether there are strong dependency in hardware between > DMAR and IR(I know IR is relying on QI). Even hardware dependency is ok, > is it ok for OS running in hardware with IR but without DMAR? Do you know a way for the IOMMU to report that DMAR is disabled, while IR is enabled? Anyhow, the VM can use IOMMU passthrough mode to avoid most IOMMU overhead. Regardless, a recent patch-set should improve DMAR performance considerably [1]. Regards, Nadav [1] https://www.mail-archive.com/iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx/msg12386.html -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
