MSI interrupts

NTDEV
1

I was looking at an old presentation on Storport and MSI, and saw a claim
that if you did not get the total number of MSI interrupts you wanted you
got one. I don’t remember this from any other discussion of MSI, and I
thought I had gotten fewer MSI interrupts than I had asked for but more than
one for a board for another purpose. So the question is:

  1. Was my memory faulty and this is the case that if you ask for N MSI
    interrupts you get N or 1, or
  2. Was this a mistake in the old presentation, or
  3. Was this the case at one point and changed, if so when, or
  4. This is something that was storport only?

Don Burn
Windows Filesystem and Driver Consulting
Website: http://www.windrvr.com
Blog: http://msmvps.com/blogs/WinDrvr

2

This has always been true under Windows, in all cases.

If you want to give yourself more choices, you have to filter in more choices when handling IRP_MN_FILTER_RESOURCE_REQUIREMENTS (which is very hard to filter from a storport miniport.)

  • Jake Oshins
    (author of the code in PCI.sys which sets up your MSI claims)
    Windows Kernel Team

-----Original Message-----
From: xxxxx@lists.osr.com [mailto:xxxxx@lists.osr.com] On Behalf Of Don Burn
Sent: Sunday, September 22, 2013 12:38 PM
To: Windows System Software Devs Interest List
Subject: [ntdev] MSI interrupts

I was looking at an old presentation on Storport and MSI, and saw a claim
that if you did not get the total number of MSI interrupts you wanted you
got one. I don’t remember this from any other discussion of MSI, and I
thought I had gotten fewer MSI interrupts than I had asked for but more than
one for a board for another purpose. So the question is:

  1. Was my memory faulty and this is the case that if you ask for N MSI
    interrupts you get N or 1, or
  2. Was this a mistake in the old presentation, or
  3. Was this the case at one point and changed, if so when, or
  4. This is something that was storport only?

Don Burn
Windows Filesystem and Driver Consulting
Website: http://www.windrvr.com
Blog: http://msmvps.com/blogs/WinDrvr

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