[vbox-dev] ICH9 BAR5 access

Ananth Pallapothu apallapothu at gmail.com
Wed Aug 19 15:22:07 GMT 2015

Hi Michal,

Not to side track every one. Here is the output of lspci as listed by VM

VBoxDbg> info phys
RAM ranges (pVM=00002aaab17d7000)
GC Phys Range                     pvHC
0000000000000000-000000009fffffff 0000000000000000 Base RAM
00000000b0000000-00000000b1ffffff 00002aaaba9ac000 VRam
00000000c0000000-00000000c001ffff 0000000000000000 E1000
00000000c0400000-00000000c07fffff 00002aaaba5a8000 VMMDev
00000000c0800000-00000000c0803fff 00002aaaba9a8000 VMMDev Heap
00000000c0804000-00000000c0804fff 0000000000000000 USB OHCI
00000000c8000000-00000000cbffffff 0000000000000000 ZebuPCIe
00000000cc000000-00000000cfffffff 0000000000000000 ZebuPCIe
00000000d0000000-00000000d01fffff 0000000000000000 ZebuPCIe
00000000d0200000-00000000d023ffff 0000000000000000 ZebuPCIe
00000000d0240000-00000000d0241fff 0000000000000000 AHCI
00000000fec00000-00000000fec00fff 0000000000000000 I/O APIC Memory
00000000fee00000-00000000fee00fff 0000000000000000 APIC Memory
00000000ffff0000-00000000ffffffff 0000000000000000 PC BIOS - 0xffffffff

apparently ICH9 never sees this passthrough device. "ZebuPCIe" device is my
VGA device name.


On Wed, Aug 19, 2015 at 11:05 AM, Michal Necasek <michal.necasek at oracle.com>

>  Yes, I agree that this does not appear to be MSI related at all. I still
> don't quite understand the utility of working with old source code with
> known bugs. What's more, we can't fix old versions, and you'll almost
> certainly need either us to fix something or tell us what to fix it. But if
> you really want to start with an old version then that's of course your
> choice.
>  I saw two VGA devices listed in your lspci output. I'm not saying it has
> to cause problems, but it is an untried/untested configuration.
>  With EFI, you should expect the firmware to initialize the BARs. That is
> the significant difference compared to the "classic" BIOS in VirtualBox.
>  Comparing DevPciIch9.cpp with DevPCI.cpp is the right thing to do,
> although there are intentional differences. The problem is very likely
> there. I'd suggest tracing ich9pciUpdateMappings() as all BAR changes
> should go through there.
>  I can also tell you right away that I have no idea how well 64-bit BARs
> work because that's a feature more or less totally unused by the VirtualBox
> devices (it only comes into play with PCI passthrough, which is very rarely
> used). FYI, the device with most BARs (six) that we have is AHCI.
>  I'm afraid I don't have any more specific suggestions because I don't
> know what your code is doing. If you can distill the problem into a
> testcase that we can look at, we'd be happy to.
>      Regards,
>            Michal
> ----- Original Message -----
> From: apallapothu at gmail.com
> To: michal.necasek at oracle.com
> Cc: vbox-dev at virtualbox.org
> Sent: Wednesday, August 19, 2015 2:46:55 PM GMT +01:00 Amsterdam / Berlin
> / Bern / Rome / Stockholm / Vienna
> Subject: Re: [vbox-dev] ICH9 BAR5 access
> Hi Michal,
>    I successfully used all BAR's with PIIX3 chipset.
>    Correct, MSI supporting is the piece forcing me move to ICH9. I
> understand changes have been made to MSI since then, but this particular
> issue doesn't seem to have anything to do with MSI, right? I was looking
> more interms of getting basic functionality of all BAR's on ICH9 working
> first before upgrading myself to latest VirtualBox.
>    My device is the VGA device. Did you find any duplicate mention
> somewhere ?
>    I will try with EFI, see if it makes any difference. What should I
> expect with this change ? Can you please recommend expected debug points in
> the source code that first invoke ICH9 BAR5 source code ?    VBoxManage
> modifyvm --name VM_name ----firmware efi
>    I tried to compare basic function calls between ICH9 vs PIIX3, but
> eventually got lost at some point. Did find some similarities using gdb
> EM.cpp -> EMHM.cpp -> HM.cpp -> DevPciIch9.cpp / DevPCI.cpp.
>    Suggestions / recommendations would really help.
> Thanks.
> On Wed, Aug 19, 2015 at 7:51 AM, Michal Necasek <michal.necasek at oracle.com
> > wrote:
>>    Hi Ananth,
>>  PCIDevSetDWord in the device won't do it, that's expected. It will get
>> rewritten.
>>  I don't think VirtualBox supplies any device with so many BARs so it's
>> entirely possible that something isn't working. The trouble is that you
>> have your code + ours, and we only have our code, so it's quite hard for us
>> to debug the problem.
>>  One hint... what happens if you switch your VM to use EFI instead of the
>> classic BIOS? I believe EFI should initialize all the PCI resources itself,
>> so you might be able to see what happens even before an OS boots.
>>  And two more comments. I see that you have both the VirtualBox VGA
>> device and your own. No one can tell you for certain that that won't cause
>> problems. And you presumably want to use MSIs (otherwise you wouldn't
>> bother with ICH9), but you're using quite old version of VirtualBox. There
>> were several fixes in the MSI handling area in VirtualBox 5.0.
>>      Regards,
>>          Michal
>> ----- Original Message -----
>> From: apallapothu at gmail.com
>> To: klaus.espenlaub at oracle.com
>> Cc: vbox-dev at virtualbox.org
>> Sent: Tuesday, August 18, 2015 9:04:05 PM GMT +01:00 Amsterdam / Berlin /
>> Bern / Rome / Stockholm / Vienna
>> Subject: Re: [vbox-dev] ICH9 BAR5 access
>> Hi Klaus,
>>     Thanks for the response.
>>     In the PCIe config space I set all BAR's to 0, using PCIDevSetDWord
>> .... no address mapping from myside.
>>     I first register the region using PDMDevHlpPCIIORegionRegister with
>> respective size.
>>                BAR0 = 0x800,0000 128 M
>>                BAR5 =     0x4,0000 256K
>>     Then I register memory call backs using PDMDevHlpMMIORegister for the
>> size.
>>      While experimenting, I played with different base address in
>> DevPciIch9.cpp "pGlobals->uPciBiosMmio = UINT32_C(0xB8000000);" which moved
>> BAR's accordingly.
>>      While experimenting, I have tried setting start address for BAR's in
>> PCIe config space, I saw that this address eventually gets overwritten by
>> FakeBIOS and then OS.
>>      When I ran lspci on the guest I did not see conflict in address
>> mapping. Attached lspci output. My pass through device shows up under VGA.
>>      I have added lspci output of fully functional PIIX3 chipset for
>> comparison.
>>     At the end of the attachment, please note the VM debugger output in
>> ICH9 chip set which apparently doesn't see the VGA device.
>>     Just to keep my message crisp, with the same device code, in PIIX3 I
>> am able to see memory access to the addresses specified in BAR0, BAR5 while
>> in ICH9, I only see access coming through in BAR0 and NOT BAR5.
>> Thanks.
>> On Tue, Aug 18, 2015 at 2:25 PM, Klaus Espenlaub <
>> klaus.espenlaub at oracle.com> wrote:
>>> Hi Ananth,
>>> On 18.08.2015 20:04, Ananth Pallapothu wrote:
>>> Hello Experts,
>>>    I have added new pass through device to the VirtualBox setup .
>>> Registered all 6 BAR's with appropriate sizes, none exceeding 256M. All
>>> BAR's were set to reflect hardware functionality (assigned 0), eventually
>>> OS programmed base address regions with the sizes I have registered them
>>> with.
>>> Can you provide more details (how you map the regions initially and on
>>> remap)? Hard to say what's happening otherwise.
>>> My fundamental problem is, I have been able to access BAR0 and NOT BAR5.
>>> I tried playing with BIOSmmio address setting in DevPciIch9, that made
>>> difference in relocating BAR's but functionality remained the same (Not
>>> able to access BAR5)
>>> Interesting part is, PIIX3 chipset is fully functional ie., can access
>>> BAR5 in PIIX3 but NOT in ICH9.
>>> Could be that with PIIX3 there's no remap and with ICH9 there's a
>>> remap... really difficult to say anything with the sparse information.
>>> Klaus
>>> PS: There seems to be some problem with my email ID, so not sure whether
>>> my last email came through. Sorry if you have already received it.
>>> Thanks.
>>> _______________________________________________
>>> vbox-dev mailing list
>>> vbox-dev at virtualbox.org
>>> https://www.virtualbox.org/mailman/listinfo/vbox-dev
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