RE: [Xen-devel] iommu support on AMD64

["Nakajima, Jun" <jun.nakajima@xxxxxxxxx>]

Langsdorf, Mark wrote:
> I'm working on getting IOMMU support enabled
> for AMD64 in Xen.
> 
> The current aperture.c code in dom0 requires
> several calls to read_pci_config() to find
> the AMD northbridge.  These calls are causing
> my system to crash.

Can you be more specific (output from serial connection, for example)?
The outl instruction causes #GP, and the emulator in Xen handle it. So,
it's possible the emulator has a bug?

> 
> read_pci_config() is defined in
> linux-2.6.12-xen0/include/asm-x86_64/pci-direct.h
> as
> 
> static inline u32 read_pci_config(u8 bus, u8 slot, u8 func, u8 offset)
> {
>       u32 v;
>       outl(0x80000000 | (bus<<16) | (slot<<11) | (func<<8) | offset,
> 0xcf8);
>       v = inl(0xcfc);
>       if (v != 0xffffffff)
>               PDprintk("%x reading 4 from %x: %x\n", slot, offset, v);
>       return v;
> }
> 
> This a specialized function intended for PCI access
> early in the boot before the PCI subsystem starts
> working.
> 
> How can I find the AMD northbridge(s) early in the
> dom0 boot sequence without crashing the system?
> 
> -Mark Langsdorf
> AMD, Inc.
> 


Jun
---
Intel Open Source Technology Center

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