IOMMU Guest Buffer Access Without Hypervisor Latency
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Solution Overview
Problem
The intervention of a hypervisor in communications between guest operating systems and an IOMMU leads to increased latency and processor load, causing delays and memory bus traffic in electronic devices with virtualization.
Innovation Solution
The IOMMU directly accesses separate buffers and logs for each guest operating system in a dedicated memory portion, eliminating the need for hypervisor intervention and using an IOMMU backing store to maintain separate MMIO registers for each guest operating system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hypervisor intervenes in communications between guest operating systems and an IOMMU, then virtualization management and control are achieved, but latency increases and processor load increases
Solution Approach 1:
The patent extracts the IOMMU communication handling function from the hypervisor and assigns it directly to the IOMMU hardware. The IOMMU now directly accesses guest buffers and logs in guest portions of memory without requiring hypervisor intervention, thereby removing the latency introduced by hypervisor processing while maintaining virtualization management through other hypervisor functions.
Solution Approach 2:
The IOMMU is empowered to service guest operating system communication requests directly without hypervisor mediation. By maintaining its own backing store with separate MMIO registers for each guest OS and directly accessing guest memory portions, the IOMMU performs self-service operations that reduce processor load and communication latency.
2Adaptability or versatility
If a hypervisor handles IOMMU communications, then resource arbitration and virtualization control are provided, but processor load increases
Solution Approach 1:
The patent extracts specific IOMMU communication handling tasks from the hypervisor's workload. The IOMMU directly manages guest buffer and log access, command processing, and event logging without hypervisor involvement, thereby reducing processor load and improving overall system productivity while the hypervisor retains high-level resource arbitration and virtualization control capabilities.
3Quantity of substance
If the IOMMU uses a single copy of buffers and logs, then memory usage is reduced, but access efficiency decreases due to hypervisor intervention
Solution Approach 1:
The patent segments memory into distinct guest portions, each with dedicated buffers and logs that the IOMMU can access directly. Each guest operating system has its own protected region in memory with separate command buffers, event logs, and PPR logs, eliminating the need for hypervisor-mediated access while improving access efficiency through direct IOMMU-to-guest-memory paths.
Data Source
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AI summary
An electronic device includes a processor that executes a guest operating system; a memory having a guest portion that is reserved for storing data and information to be accessed by the guest operating system; and an input-output memory management unit (IOMMU). The IOMMU writes, in the guest portion, information into guest buffers and/or logs used for communicating information from the IOMMU to the guest operating system. The IOMMU also reads, from the guest portion, information in guest buffers and/or logs used for communicating information from the guest operating system to the IOMMU.