Re: Why MSI is limited to 32 interrupts maximum

From: Marc Zyngier
Date: Sat Oct 15 2016 - 09:14:21 EST

On Sat, 15 Oct 2016 12:37:55 +0000
Bharat Kumar Gogada <bharat.kumar.gogada@xxxxxxxxxx> wrote:

Hi Bharat,

> Can anyone tell why MSI interrupts are limited to maximum 32
> interrupts, even though we have 16bit message data register ?

That's the very definition of the original PCI MSI: Up to 32
consecutive interrupts per function, and a single doorbell address.
MSI-X lifts that restriction and offers up to 2048 interrupts that do
not have to be contiguous can target individual doorbells. Assuming
your MSI controller advertises MSI-X support and that your devices do
support it as well, you'll be able to enjoy those.

> Regards,
> Bharat
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