Virtual PCI Root Bus Resource Allocation via Hypervisor Interception
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Solution Overview
Problem
In virtualized environments, existing systems face limitations in supporting hot-pluggable physical devices on multiple root PCI buses, as firmware does not allocate system resources to extra root buses, restricting the flexibility and efficiency of resource allocation.
Innovation Solution
The method involves a hypervisor intercepting virtual machine memory and I/O operations to present virtual PCI devices connected to a virtual PCI root bus via a virtual PCI-to-PCI bridge, allowing the guest firmware to efficiently allocate system resources to the virtual PCI root bus, enabling hot-plugging on additional root buses by pre-allocating contiguous resource ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If firmware does not allocate system resources to extra root buses, then system resource allocation remains simple and manageable, but the flexibility and efficiency of resource allocation deteriorates, preventing hot-plugging on additional root buses
Solution Approach 1:
The patent segments the system resources into separate resource pools, with each root PCI bus having its own dedicated resource pool. This allows independent allocation and management of resources for each bus, enabling hot-plugging on multiple root buses while maintaining manageable complexity through structured organization.
Solution Approach 2:
The patent implements preliminary allocation of system resources to root PCI buses during system initialization, before any hot-plugging operations occur. By pre-allocating contiguous resource ranges to each root bus, the system prepares resource pools in advance, enabling subsequent hot-plugging operations without complex real-time allocation decisions.
2Adaptability or versatility
If system resources are allocated to multiple root PCI buses, then resource allocation flexibility improves, but the difficulty of managing and tracking resource distribution increases
Solution Approach 1:
The patent divides system resources into distinct resource pools associated with each root PCI bus, creating clear boundaries and ownership for resource management. This segmentation makes it easier to track and detect resource allocation status for each bus independently, reducing the overall complexity of monitoring.
Solution Approach 2:
The patent introduces an intermediary mechanism (the resource pool structure and associated data structures) that mediates between the firmware and the actual resource allocation. This intermediary layer simplifies tracking by providing a standardized interface and centralized view of resource distribution across multiple root buses.
Data Source
AI summary
Systems and methods for allocating virtual resources to a root PCI bus. An example method may comprise: intercepting, by a hypervisor being executed by a processing device of a host computer system, a virtual machine read operation with respect to a certain address range within a Peripheral Component Interconnect (PCI) configuration space; presenting, to a virtual machine running on the host computer system, an identifier of a root PCI bus; presenting, to the virtual machine, a PCI-to-PCI bridge associated with the root PCI bus; presenting, to the virtual machine, a PCI device that is communicatively coupled to a secondary PCI bus, wherein the secondary PCI bus is communicatively coupled to the PCI-to-PCI bridge; receiving, from the virtual machine, an identifier of a resource pool associated with the PCI-to-PCI bridge; associating the resource pool with the root PCI bus; and notifying of the resource pool a guest operating system of the virtual machine.