[vbox-dev] ICH9 MSI handling

Michal Necasek michal.necasek at oracle.com
Tue Dec 29 10:36:29 GMT 2015

  I can't say much without seeing exactly what you changed. But just two 

  - Do you call pciDevSetMsi64Capable() anywhere? Perhaps MsiInit() 
should be doing that.
  - Did you set pMsiReg->fMsi64bit before registering the MSI capability?

  It is entirely possible that the 64-bit MSI support is not as good as 
it could be since VirtualBox does not ship with any devices which use that.

  Are you going to submit patches for VirtualBox or are you happy with 
maintaining local changes?

      - Michal

On 12/29/2015 5:44 AM, Ananth Pallapothu wrote:
> Hi Michal,
>     I was able to get my device working for MSI Interrupts Non-masking.
>     Problem was 3 folded.
>     1) A) Added new msiMaskEnabled function to do appropriate checkings
>         B) Existing check conditions inside MsiNotify are specifically
> isolated incase of Non-Masking.
>     2) I invoke exclusive register write access to MSI control at the
> very end of my constructor (after MSI registration call)
>     3) msiIs64Bit never returned functionally appropriate/true value. So
> I modified this function to return appropriate value by reading control
> config & 0x80
> Thanks.
> On Mon, Dec 28, 2015 at 4:50 AM, Michal Necasek
> <michal.necasek at oracle.com <mailto:michal.necasek at oracle.com>> wrote:
>       Hmm, that doesn't make sense to me. The mask bits do not overlap
>     anything else. I'm looking at figure 6-9 on page 233 of the PCI 3.0
>     specification.
>       The code in MsiCommon.cpp is clear enough. Are you failing to set
>     the fMsi64bit flag when registering the MSI capability?
>       You probably also noticed that MsiInit() always sets the
>     BOX_PCI_MSI_FLAGS_MASKBIT and there is currently no way to register
>     an emulated device without MSI per-vector masking. That should not
>     cause trouble since guest software does not have to use masking.
>           - Michal
>     ----- Original Message -----
>     From: apallapothu at gmail.com <mailto:apallapothu at gmail.com>
>     To: vbox-dev at virtualbox.org <mailto:vbox-dev at virtualbox.org>
>     Sent: Monday, December 21, 2015 5:16:15 AM GMT +01:00 Amsterdam /
>     Berlin / Bern / Rome / Stockholm / Vienna
>     Subject: [vbox-dev] ICH9 MSI handling
>     Hello Developers,
>            I am experimenting on ICH9 with a pluggable device. Reason
>     for using ICH9 is MSI support.
>     Following through AHCI, HPET device I see that code is aligned for
>     specific mode of MSI configuration, "Per-Vector Masking Capable".
>            MsiNotify function reads Mask Bits, Pending Bits without
>     conditionally checking whether device is Per-Vector Masking Capable.
>     So, by default code thinks offset 0xC reg as mask data where infact
>     it is MSI data with Interrupt Vector ID incase of masking disabled.
>     iVector value seems to be confusing too.
>           My particular device needs to be configured for 64 bit MSI
>     address capable and Mask disabled, so, MSI_MSG_CNTL @ MSI capability
>     offset 0x02 = 0x0081
>          Can someone please suggest, recommend changes to handle this
>     mode of MSI operation ?
>     Thanks.

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