Bug 5277

Summary: 32-bit server cannot handle PCI devices above 0x00000000ffffffff
Product: xorg Reporter: Ian Romanick <idr>
Component: Server/GeneralAssignee: Xorg Project Team <xorg-team>
Status: CLOSED FIXED QA Contact: Xorg Project Team <xorg-team>
Severity: normal    
Priority: high    
Version: unspecified   
Hardware: Other   
OS: Linux (All)   
Whiteboard:
i915 platform: i915 features:
Bug Depends on:    
Bug Blocks: 433    

Description Ian Romanick 2005-12-08 08:13:08 UTC 
On 64-bit PowerPC, and possibly other architectures, PCI devices are mapped
above the 32-bit barrier.  When X is built as a 32-bit binary, which is typical
on PowerPC, it cannot access these devices.  X tries to map the BAR as an offset
to /dev/mem.  Since the offset is larger than the offset parameter to mmap, the
wrong address is mapped.  The result is that either random locations in system
memory are used or a bus error is generated (I've seen both).

At least on Linux, the correct solution is to use
/sys/bus/pci/devices/*/resource* instead of /dev/mem.  By doing this, the offset
to mmap would always be zero.
Comment 1 Daniel Stone 2007-02-27 01:29:17 UTC 
Sorry about the phenomenal bug spam, guys.  Adding xorg-team@ to the QA contact so bugs don't get lost in future.
Comment 2 Ian Romanick 2008-06-02 07:50:44 UTC 
PCI-rework has landed, and this bug is no longer relevant.

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