Xen project Mailing List

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=0x00008086 len=2
pt_pci_read_config: [00:06.0]: address=0002 val=0x00001e20 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

[Xen-devel] 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)