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

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Wed, 14 Oct 2009, Bruce Edge wrote:
> 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 ?
>

in the same file: pt-msi.c.

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