MSI-X (first defined in PCI 3.0) permits a device to allocate up to 2048 interrupts. The single address used by original MSI was found to be restrictive for some architectures.

When MSI-X is supported, you need to specify the size and the location (BARs and offsets) of the MSI-X table and Pending Bit Array (PBA). MSI-X can support up to 2048 vectors per function versus 32 vectors per function for MSI.

PCI/PCIe设备通过在其PCI Configuration Space中实现MSI/MSI-X Capability Registers来向系统软件表明是否支持MSI/MSI-X。 MSI/MSI-X Capability Registers属于传统的Basic PCI Capability Structure，其组成包括：

Host software sets up the MSI-X interrupts in the Application Layer by completing the following steps: Host software reads the Message Control register at 0x050 register to determine the MSI-X Table size.

The MSI-X Capability Structure contains information about the MSI-X Table and PBA Structure. For example, it contains pointers to the bases of the MSI-X Table and PBA Structure, expressed as offsets from the addresses in the function's BARs.

2025年2月21日 · Message-signaled interrupts (MSIs) were introduced in the PCI 2.2 specification as an alternative to line-based interrupts. Instead of using a dedicated pin to trigger interrupts, devices that use MSIs trigger an interrupt by writing a value to a particular memory address.

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2023年10月23日 · MSI-X, also known as Message Signaled Interrupts, is a technique that allows a device to interrupt a processor with only a single message. With MSI-X, a device can send an interrupt message to the processor, which will cause the processor to …

2023年3月13日 · Message-signaled interrupts (MSIs) provide an alternative to traditional line-based interrupts that network devices and their miniport drivers can use. Starting with Windows Vista, the operating system supports two types of MSIs: PCI V2.2 MSI and PCI V3.0 MSI-X.

MSI-X is an optional feature that provides a method of in-band signaling of an interrupt. This feature enables a device function to request service by writing a system-specified data value to a system-specified address. System software initializes the message address and message data during device configuration.