I think the issue that we are seeing, is related to the kernel thinking
that the graphics card memory is uncachable. If the mtrr tables are
changed such that the memory at d0000000 is set to write-back rather
than uncachable
So:
reg00: base=0xd0000000 (3328MB), size= 256MB: uncachable, count=1
is changed to
reg00: base=0xd0000000 (3328MB), size= 256MB: write-back, count=1
This guess is due to the line starred below (***) ... found by sudo lspci -vv
and what appears to be the congruent line in the mtrr tables.
01:00.0 VGA compatible controller: ATI Technologies Inc Radeon HD 3870 (prog-if
00 [VGA controller])
Subsystem: Hightech Information System Ltd. Unknown device 2003
Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr-
Stepping- SERR- FastB2B-
Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort-
<MAbort- >SERR- <PERR-
Latency: 0, Cache Line Size: 32 bytes
Interrupt: pin A routed to IRQ 16
*** Region 0: Memory at d0000000 (64-bit, prefetchable) [size=256M] ***
Region 2: Memory at fe8e0000 (64-bit, non-prefetchable) [size=64K]
Region 4: I/O ports at c000 [size=256]
Expansion ROM at fe8c0000 [disabled] [size=128K]
Capabilities: [50] Power Management version 3
Flags: PMEClk- DSI- D1+ D2+ AuxCurrent=0mA
PME(D0-,D1-,D2-,D3hot-,D3cold-)
Status: D0 PME-Enable- DSel=0 DScale=0 PME-
Capabilities: [58] Express Legacy Endpoint IRQ 0
Device: Supported: MaxPayload 128 bytes, PhantFunc 0, ExtTag+
Device: Latency L0s <4us, L1 unlimited
Device: AtnBtn- AtnInd- PwrInd-
Device: Errors: Correctable- Non-Fatal- Fatal- Unsupported-
Device: RlxdOrd+ ExtTag- PhantFunc- AuxPwr- NoSnoop+
Device: MaxPayload 128 bytes, MaxReadReq 128 bytes
Link: Supported Speed 2.5Gb/s, Width x16, ASPM L0s L1, Port 0
Link: Latency L0s <64ns, L1 <1us
Link: ASPM Disabled RCB 64 bytes CommClk+ ExtSynch-
Link: Speed 2.5Gb/s, Width x16
Capabilities: [a0] Message Signalled Interrupts: Mask- 64bit+ Queue=0/0
Enable-
Address: 0000000000000000 Data: 0000
--
MTRR is not properly setup on Intel Northbridge Chipset (P35, X38, X48) with
more than 3GB RAM and with Memory Remapping Enabled
https://bugs.launchpad.net/bugs/224404
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