# [SOLVED] CONFIG_X86_INTEL_TSX_MODE_OFF=y

## charles17

Kernel update from 4.19.82 to 4.19.86 gives me new options:

```
$ diff <(cat .config | sort) <(cat .config.old | sort)

3607,3609d3606

< # CONFIG_X86_INTEL_TSX_MODE_AUTO is not set

< CONFIG_X86_INTEL_TSX_MODE_OFF=y

< # CONFIG_X86_INTEL_TSX_MODE_ON is not set

3755c3752

< # Linux/x86 4.19.86-gentoo Kernel Configuration

---

> # Linux/x86 4.19.82-gentoo Kernel Configuration
```

Kernel help says

```
Intel's TSX (Transactional Synchronization Extensions) featureallows to optimize locking protocols through lock elision which                                                                                                                                                                                                                                                        

can lead to a noticeable performance boost.

On the other hand it has been shown that TSX can be exploited

to form side channel attacks (e.g. TAA) and chances are there

will be more of those attacks discovered in the future.

Therefore TSX is not enabled by default (aka tsx=off). An admin

might override this decision by tsx=on the command line parameter.

Even with TSX enabled, the kernel will attempt to enable the best

possible TAA mitigation setting depending on the microcode available

for the particular machine.

This option allows to set the default tsx mode between tsx=on, =off

and =auto. See Documentation/admin-guide/kernel-parameters.txt for more

details.

Say off if not sure, auto if TSX is in use but it should be used on safe

platforms or on if TSX is in use and the security aspect of tsx is not

relevant.

Prompt: TSX enable mode

   Location:

     -> Processor type and features

   Defined at arch/x86/Kconfig:1906

   Depends on: CPU_SUP_INTEL [=y]

   Selected by [m]:

   - CPU_SUP_INTEL [=y] && m
```

What are your thoughts, should I leave it as is?  I don't even know what TSX is.Last edited by charles17 on Tue Nov 26, 2019 3:25 pm; edited 1 time in total

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## PrSo

Since I have Haswell CPU I turned tsx off.

On Haswel microarchitecture it is implemented but disabled by Intel on microcode level as a buggy one.

https://www.anandtech.com/show/8376/intel-disables-tsx-instructions-erratum-found-in-haswell-haswelleep-broadwelly

Anyway TSX is used mostly on server environment.

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## CaptainBlood

https://www.phoronix.com/scan.php?page=news_item&px=ZombieLoad-TAA-Announced

https://lwn.net/Articles/804462/#Comments

Starting from intel Haswell & above CPUs.

Thks 4 ur attention

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## charles17

Thanks for the advices.

So for i7-3740QM in Dell Latitude E6430 I wouldn't have to care about.

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## CaptainBlood

Likely to be right assuming Sandy/Ivy bridge generation.

Thks 4 ur attention, interest & support.

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