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Transactional Synchronization Extensions

Transactional Synchronization Extensions (TSX), also called Transactional Synchronization Extensions New Instructions (TSX-NI), is an extension to the x86 instruction set architecture (ISA) that adds hardware transactional memory support, speeding up execution of multi-threaded software through lock elision. According to different benchmarks, TSX/TSX-NI can provide around 40% faster applications execution in specific workloads, and 4–5 times more database transactions per second (TPS).[1][2][3][4]

TSX/TSX-NI was documented by Intel in February 2012, and debuted in June 2013 on selected Intel microprocessors based on the Haswell microarchitecture.[5][6][7] Haswell processors below 45xx as well as R-series and K-series (with unlocked multiplier) SKUs do not support TSX/TSX-NI.[8] In August 2014, Intel announced a bug in the TSX/TSX-NI implementation on current steppings of Haswell, Haswell-E, Haswell-EP and early Broadwell CPUs, which resulted in disabling the TSX/TSX-NI feature on affected CPUs via a microcode update.[9][10]

In 2016, a side-channel timing attack was found by abusing the way TSX/TSX-NI handles transactional faults (i.e. page faults) in order to break kernel address space layout randomization (KASLR) on all major operating systems.[11] In 2021, Intel released a microcode update that disabled the TSX/TSX-NI feature on CPU generations from Skylake to Coffee Lake, as a mitigation for discovered security issues.[12]

Support for TSX/TSX-NI emulation is provided as part of the Intel Software Development Emulator.[13] There is also experimental support for TSX/TSX-NI emulation in a QEMU fork.[14]

  1. ^ Richard M. Yoo; Christopher J. Hughes; Konrad Lai; Ravi Rajwar (November 2013). "Performance Evaluation of Intel Transactional Synchronization Extensions for High-Performance Computing" (PDF). intel-research.net. Archived from the original (PDF) on 2016-10-24. Retrieved 2013-11-14.
  2. ^ Tomas Karnagel; Roman Dementiev; Ravi Rajwar; Konrad Lai; Thomas Legler; Benjamin Schlegel; Wolfgang Lehner (February 2014). "Improving In-Memory Database Index Performance with Intel Transactional Synchronization Extensions" (PDF). software.intel.com. Retrieved 2014-03-03.
  3. ^ "Performance Evaluation of Intel Transactional Synchronization Extensions for High Performance Computing". supercomputing.org. November 2013. Archived from the original on 2013-10-29. Retrieved 2013-11-14.
  4. ^ "Benchmarks: Haswell's TSX and Memory Transaction Throughput (HLE and RTM)". sisoftware.co.uk. Retrieved 2013-11-14.
  5. ^ "Transactional Synchronization in Haswell". Software.intel.com. Retrieved 2012-02-07.
  6. ^ "Transactional memory going mainstream with Intel Haswell". Ars Technica. 2012-02-08. Retrieved 2012-02-09.
  7. ^ "The Core i7-4770K Review". Tom's Hardware. 2013-06-01. Retrieved 2012-06-03.
  8. ^ "Intel Comparison Table of Haswell Pentium, i3, i5, and i7 models". intel.com. Retrieved 2014-02-11.
  9. ^ Scott Wasson (2014-08-12). "Errata prompts Intel to disable TSX in Haswell, early Broadwell CPUs". techreport.com. Retrieved 2014-08-12.
  10. ^ "Desktop 4th Generation Intel Core Processor Family, Desktop Intel Pentium Processor Family, and Desktop Intel Celeron Processor Family: Specification Update (Revision 014)" (PDF). Intel. June 2014. p. 46. Retrieved 2014-08-13. Under a complex set of internal timing conditions and system events, software using the Intel TSX/TSX-NI (Transactional Synchronization Extensions) instructions may observe unpredictable system behavior.
  11. ^ "Breaking Kernel Address Space Layout Randomization with Intel TSX" (PDF). 2016.
  12. ^ Gareth Halfacree (2021-06-29). "Intel sticks another nail in the coffin of TSX with feature-disabling microcode update". The Register. Retrieved 2012-10-17.
  13. ^ Wooyoung Kim (2013-07-25). "Fun with Intel Transactional Synchronization Extensions". Intel. Retrieved 2013-11-12.
  14. ^ Sebastien Dabdoub; Stephen Tu. "Supporting Intel Transactional Synchronization Extensions in QEMU" (PDF). mit.edu. Retrieved 2013-11-12.

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