Windows System Software -- Consulting, Training, Development -- Unique Expertise, Guaranteed Results

Sept/Oct 2019 Issue of The NT Insider available


Download PDF here: http://insider.osr.com/2019/ntinsider_2019_01.pdf

It’s a particularly BIG issue, too: 40 pages of technical goodness, ranging from WDF to Minifilters. Check it out.
Before Posting...
Please check out the Community Guidelines in the Announcements and Administration Category.

MSI-X / Interrupt Affinity

msrmsr Member Posts: 338
edited September 8 in NTDEV

Hi

I have multiple MSI in old hw.
Vectors used by all interrupt events are driver configurable, so even if I get less MSI, I know the MsgID semantics. SW/FW did handshake etc.

I see my ISR is programmed in the IDT of all processors.
-Why is this required if ALL my MSI vectors are/can be targeted only to a specific processor.?
-Couldn't windows instead grant all my vectors, by finding a proc with enough free IDT entries instead of trying to find enough free entries in all procs?

I am trying to get MSI-X into my new device/fw and driver.

1) Spec - Function can have MSI or MSI-X or both, but only 1 enabled.
I guess in this case windows enables only MSI-X. Can HW just do away with MSI altogether and just do MSI-X?

2) Spec - Handling MSI-X Vector Shortages (--> Multiple MSI-X Table entries can have same vector)
But anyways windows grants either 1 or ALL MSI-X. In case only 1 MSI-X, how the MSI-X.Table (MsgCtrl.TableSize is > 1) configured
a) All MSI-X entries are (unmasked and) set to vector 0
b) Only MSI-X.TableEntry[0] is set to vector 0 and rest remain masked, and then FW doesn't/shouldn't generate/use those events/entries.

2.1) Also whose responsibility, driver or OS, to update the MSI-X table?
Seems mostly it is the OS task, but when is driver supposed to use this PCI_MSIX_TABLE_CONFIG_INTERFACE?

3) Seems IRP_MN_FILTER_RESOURCE_REQUIREMENTS is used to pin a particular MSI-X vector/interrupt to a particular core in KMDF driver (like it is done for NDIS/RSS).
In this case does the ISR for that vector is set only on that specific processor IDT (assume each of my interrupt/vector is using distinct Isr()?

Thanks

Post edited by msr on
Sign In or Register to comment.

Howdy, Stranger!

It looks like you're new here. If you want to get involved, click one of these buttons!

Upcoming OSR Seminars
Writing WDF Drivers 21 Oct 2019 OSR Seminar Space & ONLINE
Internals & Software Drivers 18 Nov 2019 Dulles, VA
Kernel Debugging 30 Mar 2020 OSR Seminar Space
Developing Minifilters 27 Apr 2020 OSR Seminar Space & ONLINE