[vbox-dev] ICH9 MSI handling

Ananth Pallapothu apallapothu at gmail.com
Tue Dec 29 23:29:59 UTC 2015


2 things that I do 1) Directly write to control config register for 64 bit
using *setbyte or *setword function calls 2) I set "pMsiReg->fMsi64bit"
during MSI registration.

I presume changes might help other users, so would be glad to submit
changes. Never submitted patches before, what is the process to do so ?

Ananth

On Tue, Dec 29, 2015 at 5:36 AM, Michal Necasek <michal.necasek at oracle.com>
wrote:

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