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

On Tue, 13 Oct 2009, Cinco, Dante wrote:
> I get the above error message when I boot the domU (Linux I'm 
> using Xen 3.5-unstable (changeset 20303) with
> pv_ops kernel 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 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.
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