I am trying to use MSI for my network card. After setting the MSI slot in the PCI configuration block based on Intel manual, I can confirm the interrupt is delivered to the processor's local APIC by looking at the IRR content in kernel debugger. The bit in IRR that reflects the vector I specified in MSI message is set to 1 by APIC. However, the interrupt handler installed at that vector is never invoked. Does someone have any idea on this? The priority does not seem to be the issue, because I checked the TPR, which was 0x80 when I entered kernel debugger and decreased to 0 when I press 'g'. The error status register is also zero in the kernel debugging mode, while there is a pending interrupt request as suggested by IRR. But the cpu just can't get the interrupt. Any suggestions? Thanks.