Re: [Xen-devel] pt_msix_init: Error: Can't map physical MSI-X table: Invalid argument

[Bruce Edge <bruce.edge@xxxxxxxxx>]

On Wed, Oct 14, 2009 at 5:47 AM, Stefano Stabellini
<stefano.stabellini@xxxxxxxxxxxxx> wrote:
> On Tue, 13 Oct 2009, Cinco, Dante wrote:
>> I get the above error message when I boot the domU (Linux 2.6.30.1). I'm 
>> using Xen 3.5-unstable (changeset 20303) with
>> pv_ops kernel 2.6.31.1. I use pci-stub to hide the device so that I can 
>> assign/pass it through to domU. The error is
>> coming from ioemu-xxx/hw/pt-msi.c. I think it is complaining about the 
>> table_off that is part of the mmap() call:
>>
>>     dev->msix->phys_iomem_base = mmap(0, total_entries * 16,
>>                           PROT_WRITE | PROT_READ, MAP_SHARED | MAP_LOCKED,
>>                           fd, dev->msix->table_base + table_off);
>>
>> When I printed table_off, its value is 0x4100 (not page-aligned) which is 
>> consistent with the BAR4 offset of the PCI
>> device (see below). I think mmap() requires the last argument to be a 
>> multiple of the page size and results is a map
>> error if it is not. Here's the partial output of "lspci -vv -s 0:07:0.1" 
>> from dom0:
>>
>> 07:00.0 Fibre Channel: PMC-Sierra Inc. Device 8032 (rev 05)
>>         Subsystem: Atto Technology Device 003c
>>         Latency: 0, Cache Line Size: 64 bytes
>>         Interrupt: pin A routed to IRQ 11
>>         Capabilities: [60] Message Signalled Interrupts: Mask- 64bit+ 
>> Queue=0/1 Enable+
>>                 Address: 00000000fee11000  Data: 405e
>>         Capabilities: [70] Express (v2) Endpoint, MSI 01
>>                 DevCap: MaxPayload 4096 bytes, PhantFunc 0, Latency L0s 
>> <4us, L1 unlimited
>>                         ExtTag- AttnBtn- AttnInd- PwrInd- RBE+ FLReset-
>>         Capabilities: [b0] MSI-X: Enable- Mask- TabSize=9
>>                 Vector table: BAR=4 offset=00004100
>>                 PBA: BAR=4 offset=00004000
>>
>> I'm able to workaround this problem by modifying pt-msi.c: force offset to 
>> zero in mmap() and on the next line, adjust
>> the pointer by table_off:
>>
>>     table_off_adjust = table_off & 0x0fff;
>>     dev->msix->phys_iomem_base = mmap(0, total_entries * 16 + 
>> table_off_adjust,
>>                           PROT_WRITE | PROT_READ, MAP_SHARED | MAP_LOCKED,
>>                           fd, dev->msix->table_base + table_off - 
>> table_off_adjust);
>>     dev->msix->phys_iomem_base = (void *)((char *)dev->msix->phys_iomem_base 
>> + table_off_adjust);
>>
>> Ideally, I should only be applying this to my device but since I'm not 
>> passing any other device that use MSI, I don't see
>> any negative effect. In addition, my device only uses MSI and not MSI-X.
>>
>> Obviously, this is a custom hack but I was wondering if there is a cleaner 
>> solution for this. Is a non-page aligned BAR
>> offset unusual? When I boot Linux 2.6.30.1 on bare metal (no Xen), I don't 
>> see this error.
>
> I think this workaround is not so bad, you just need to keep
> table_off_adjust around because it has to be used in munmap too.

Where is the respective munmap call ?

-Bruce

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