Re: Inconsistent MSI flags for pure HVM guest in 4.1.3 with the back-ported 4.2.0 msi_retranslate patch. (Was: Issue about domU missing interrupt)

["G.R." <firemeteor@users.sourceforge.net>]

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Hi, could anybody take a look please?


On Thu, Dec 6, 2012 at 11:42 AM, G.R. <firemeteor@users.sourceforge.net>wrote:

> Sorry, but I have to resend this in a separate thread for better
> visibility.
> Back ground:
> After backporting this patch to fix my PVHVM interrupt missing issue in
> 4.1.3:
> http://lists.xen.org/archives/html/xen-devel/2012-06/msg01909.html
> I find side effect for pure HVM guest.
> http://lists.xen.org/archives/html/xen-devel/2012-12/msg00208.html
>
> I had a follow up thread to analysis the issue and post it again here:
>
> Hi, it seems that the patch has some side effect on pure HVM guest.
>>> For openelec 2.0 guest, which is based on linux 3.2.x with PVOP
>>> disabled, I see such syndrome in qemu-dm-xxx.log:
>>>
>>> pt_msgaddr64_reg_write: Error: why comes to Upper Address without 64 bit
>>> support??
>>> pt_pci_write_config: Internal error: Invalid write emulation return
>>> value[-1]. I/O emulator exit.
>>>
>>> The guest dies immediately after the log, I have no way to check guest
>>> kernel log.
>>> Without the patch, this guest can boot without obvious error log even
>>> the VGA passthrough does not quite work.
>>> I'll check the code to see what does these log mean...
>>>
>>
>> I did some analysis and it really looks like a bug to me.
>> Since this is a patch back-ported from 4.2.0, I would like to ask is
>> there any follow up patch that would fix this issue?
>> Please see my analysis below:
>>
>> Here is part of the qemu-dm log, with debug log enabled at compile time:
>>
>> dm-command: hot insert pass-through pci dev
>> register_real_device: Assigning real physical device 00:1b.0 ...
>> pt_iomul_init: Error: pt_iomul_init can't open file /dev/xen/pci_iomul:
>> No such file or directory: 0x0:0x1b.0x0
>> pt_register_regions: IO region registered (size=0x00004000
>> base_addr=0xf7c10004)
>> pt_msi_setup: msi mapped with pirq 36
>> pci_intx: intx=1
>> register_real_device: Real physical device 00:1b.0 registered successfuly!
>> IRQ type = MSI-INTx
>> ...
>> pt_pci_read_config: [00:06.0]: address=0000 val=0x0000*8086* len=2
>> pt_pci_read_config: [00:06.0]: address=0002 val=0x0000*1e20* len=2
>> ...
>> *pt_pci_write_config: [00:06.0]: address=0068* val=0x00000000 len=4
>> ...
>> pt_pci_write_config: [00:06.0]: address=0062 val=0x00000081 len=2
>> *pt_msgctrl_reg_write: guest enabling MSI, disable MSI-INTx translation*
>> pci_intx: intx=1
>> *pt_msi_disable: Unmap msi with pirq 36*
>> pt_msgctrl_reg_write: setup msi for dev 30
>> pt_msi_setup: msi mapped with pirq 36
>> pt_msi_update: Update msi with pirq 36 gvec 51 gflags 1303
>> pt_pci_read_config: [00:06.0]: address=0062 val=0x00000081 len=2
>> pt_pci_write_config: [00:06.0]: address=0062 val=0x00000081 len=2
>> pt_pci_write_config: [00:06.0]: address=0064 val=0xfee0300c len=4
>> *pt_pci_write_config: [00:06.0]: address=0068* val=0x00000000 len=4
>>
>> pt_msgaddr64_reg_write: Error: why comes to Upper Address without 64 bit
>> support??
>> pt_pci_write_config: Internal error: Invalid write emulation return
>> value[-1]. I/O emulator exit.
>>
>>
>> Here the device in question should is the audio controller, 00:1b.0 in
>> the host, which is 64 bit capable:
>> 00:1b.0 Audio device: Intel Corporation 7 Series/C210 Series Chipset
>> Family High Definition Audio Controller (rev 04)
>>     Capabilities: [60] MSI: Enable+ Count=1/1 Maskable- 64bit+
>>         Address: 00000000fee00378  Data: 0000
>>
>> And there is also a successful write to offset 0x68 above, while the
>> second write fails the I/O emulator.
>>
>>
>> The patch added pt_msi_disable() call into *pt_msgctrl_reg_write() *function,
>> And the pt_msi_disable() function has these lines:
>> out:
>>     /* clear msi info */
>>     dev->msi->flags = 0;
>>     dev->msi->pirq = -1;
>>     dev->msi_trans_en = 0;
>>
>> As a result, the flags are cleared -- this is new to the patch.
>> And I believe this change caused the failure in pt_msgaddr64_write():
>>
>> 3882     /* check whether the type is 64 bit or not */
>> 3883     if (!(ptdev->msi->flags & PCI_MSI_FLAGS_64BIT))
>> 3884     {
>> 3885         /* exit I/O emulator */
>> 3886         PT_LOG("Error: why comes to Upper Address without 64 bit
>> support??\n");
>> 3887         return -1;
>> 3888     }
>>
>>
>> I only see flags setup in  pt_msgctrl_reg_init() function. I guess this
>> is not called this time.
>>
>> Thanks,
>> Timothy
>>
>
>
>
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