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A comment on iMac Pro's T2 chip. Parent comment

Re:iMac Pro's T2 chip by bitwize on Thursday January 04, 2018 @12:59PM (#16072426)
Ever hear of DMA, dude?
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Re:iMac Pro's T2 chip by turblety on Thursday January 04, 2018 @01:01PM (#16072450)
Isn't that a feature of the CPU though?

*edit sorry I am wrong. DMA seems to bypass the CPU [1]

1. https://www.csoonline.com/article/2607924/security/stop-snea...

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Re:iMac Pro's T2 chip by godelmachine on Thursday January 04, 2018 @01:05PM (#16072503)
I was about to correct you when you edited your own comment !! :)
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Re:iMac Pro's T2 chip by j_coder on Thursday January 04, 2018 @03:23PM (#16073729)
Not having a central controller multiple subsystem vendors would have to cooperate using an agreed DMA communication protocol to monitor you and send the information back using the wifi/ethernet chip. Possible but unlikely.
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Re:iMac Pro's T2 chip by jnwatson on Thursday January 04, 2018 @06:12PM (#16074988)
The DMA communication protocol is already defined. It is part of PCIExpress.
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Re:iMac Pro's T2 chip by walterbell on Thursday January 04, 2018 @11:16PM (#16076485)
On the iMac Pro, will PCI devices be able to DMA into both the Intel and ARM CPUs? Is there a single IOMMU which will arbitrate DMA for both CPUs?
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Re:iMac Pro's T2 chip by jnwatson on Thursday January 11, 2018 @02:40AM (#16122103)
The IOMMU functionality is built into the Platform Controller Hub, which is between the baseboard management controller (the ARM) and the main processor.

Theoretically it would be possible to prevent DMA between the two, but it is highly doubtful Apple would program it that way.

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Re:iMac Pro's T2 chip by wang_li on Thursday January 04, 2018 @01:09PM (#16072531)
This is what an IOMMU is for.
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