Faster NFS, PCIe DMA attacks, and undervolting CPUs

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Moonstone Man
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Faster NFS, PCIe DMA attacks, and undervolting CPUs

Post by Moonstone Man »

There are three interesting articles on Phoronix today:

https://www.phoronix.com/scan.php?page= ... Linux-5.10

Kernel 5.10 sees NFS performance changes for handling sparse files.

As an aside, I like the phrase, "efficiently transferring holes". For those not familiar with sparse files, the thought of transferring a hole from one place to another would probably cause a good dose of cognitive dissonance.

https://www.phoronix.com/scan.php?page= ... olt-Kernel

There have been a few posts on the forum about undervolting laptop CPUs, and now it's being discussed for the kernel.

https://www.phoronix.com/scan.php?page= ... x-5.10-PCI

For those of you not familiar with DMA attacks: https://en.wikipedia.org/wiki/DMA_attack
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absque fenestris
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Re: Faster NFS, PCIe DMA attacks, and undervolting CPUs

Post by absque fenestris »

About DMA attacks: is that the price for a stable connection?

It reminds me of the reviews FireWire (on the Mac) received.
Only - in contrast to the nominally faster USB-2 (480 Mbits), FireWire 400 (400 Mbits) delivered almost the promised performance reliably and permanently, as did FireWire 800 later.
USB-2 was a disaster on the Mac and here in the Mint forums you read again and again about terrible USB-2 connections in Windows machines.
In the meantime, USB-C (the latest generations) and Thunderbolt seem to be slowly growing together - is USB-C likely to be exposed to these DMA attacks at some point?
Moonstone Man
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Re: Faster NFS, PCIe DMA attacks, and undervolting CPUs

Post by Moonstone Man »

absque fenestris wrote: Thu Oct 22, 2020 9:20 pm ... is USB-C likely to be exposed to these DMA attacks at some point?
You didn't read the wiki link, did you.
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absque fenestris
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Re: Faster NFS, PCIe DMA attacks, and undervolting CPUs

Post by absque fenestris »

Kadaitcha Man wrote: Thu Oct 22, 2020 11:03 pm
absque fenestris wrote: Thu Oct 22, 2020 9:20 pm ... is USB-C likely to be exposed to these DMA attacks at some point?
You didn't read the wiki link, did you.
I read it twice - and also the entry about Thunderbolt - now maybe it only affects the next generation of USB ...
USB4
Main article: USB4
The USB4 specification was released on 29 August 2019 by USB Implementers Forum,[67] based on the Thunderbolt 3 protocol specification.[68]

It supports 40 Gbit/s (5 GB/s) throughput, is compatible with Thunderbolt 3, and backwards compatible with USB 3.2 and USB 2.0.[69][70] The architecture defines a method to share a single high-speed link with multiple end device types dynamically that best serves the transfer of data by type and application.

Thunderbolt 4
Thunderbolt 4 was announced at CES 2020[71] and the final specification was released in July 2020.[72] The key differences between Thunderbolt 4 and Thunderbolt 3 are support for USB4 protocol and data rates, a minimum bandwidth requirement of 32 Gbps for PCIe link, support for dual 4K displays, and Intel VT-d-based direct memory access protection to prevent physical DMA attacks. The maximum bandwidth remains at 40 Gbps, the same as Thunderbolt 3 and four times faster than USB 3.2 Gen2x1.[73][72] Supporting products should arrive in 2020 and will include Tiger Lake mobile processors for Project Athena notebooks and 8000-series standalone Thunderbolt controllers.
https://en.wikipedia.org/wiki/Thunderbolt_(interface)
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