Re: [Xen-devel] Issue with MSI in a HVM domU with several passed through PCI devices

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 20.06.12 at 15:58, Rolu <rolu@xxxxxxxx> wrote:
> On Tue, Jun 19, 2012 at 11:45 AM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
>> Unless this is in the guest kernel, we'll likely need a code fix here,
>> but for determining what and where, we'd need you to provide
>> the qemu log for the domain as well (there ought to be entries
>> starting with "Update msi with pirq", and the gflags value is of
>> particular interest). Depending on what we see, we may then
>> need you to do some further debugging.
>>
> 
> There are, these: (I've copied the full logs below)
> 
> pt_msi_update: Update msi with pirq 37 gvec 0 gflags 3031
> pt_msi_update: Update msi with pirq 36 gvec 0 gflags 3030
> pt_msi_update: Update msi with pirq 35 gvec 0 gflags 302f

Okay, so at that point the bad value is already there. I'd
suggest taking it up the usage chain, so adding some logging
in pt_msgdata_reg_write() (where the original value -
ptdev->msi->data - is being computed) would likely be a
good first step.

At the same time, adding logging to the guest kernel would
be nice, to see what value it actually writes (in a current
kernel this would be in __write_msi_msg()).

> The qemu logs give several errors and warnings, such as (there are
> multiple of each of these):
> 
> pt_iomul_init: Error: pt_iomul_init can't open file
> /dev/xen/pci_iomul: No such file or directory: 0x1:0x0.0x0
> pt_pci_write_config: [00:05:0] Warning: Guest attempt to set address
> to unused Base Address Register. [Offset:30h][Length:4]
> pt_pci_read_config: [00:10:0] Error: Failed to read register with
> offset exceeding FFh. [Offset:ffh][Length:1]
> 
> Are these related, and/or cause for worry? I've looked around some but
> apart from the fact that they have to do with PCI it doesn't tell me
> much. They occur no matter whether I use pci=nomsi or not.

I don't know.

Jan


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