The original FPU lazy restore vulnerability (CVE-2018-3665) allowed a malicious process to read FPU state from another process (including cryptographic keys in FPU registers). VSO is a mitigation enabler but not a silver bullet.
With VSO:
Verdict: VSO + Eager FPU is more secure than lazy FPU, but not more secure than eager FPU with a fixed buffer.
If a thread modifies only part of its vector state (e.g., only XMM0), VSO allows saving only the modified components rather than the entire FPState. fpstate vso
Before understanding VSO, you must understand FPState.
FPState is simply the data structure holding all these registers.
In a virtualized environment, managing the fpstate efficiently is critical for ensuring that virtual machines (VMs) or containers operate correctly and leverage the host machine's floating-point capabilities. Here, VSO might refer to operations or management tasks related to virtual servers. Verdict: VSO + Eager FPU is more secure
No. The VA only recognizes one accredited representative at a time.
If you have a VSO (e.g., DAV) and then sign a contract with an attorney, the VA requires you to revoke the VSO’s POA using VA Form 21-22 (Revocation). You will then file VA Form 21-22a naming the attorney as your FPSTATE representative.
Warning: Switching representatives mid-claim can cause delays. Your old VSO must release the file, and the new attorney must get "up to speed." FPState is simply the data structure holding all
There is no universal "right" answer, but there is a strategic rule of thumb:
The bottom line: A VSO is your friend in the trenches. An FPSTATE attorney is your sniper for difficult targets. Do not let ego stop you from hiring an attorney if your claim is worth more than $50,000 in back pay. Most attorneys only get paid if you win, so they will only take your case if they believe in it.
In the world of systems programming, the management of processor state—specifically floating-point (FP) and SIMD (Single Instruction, Multiple Data) registers—is a constant battle between performance and complexity.
If you’ve been following recent developments in the Linux kernel or high-performance runtime environments, you may have come across the term fpstate vso (often appearing in the context of fpstate reworks and Variable State Objects).
But what exactly is a VSO in this context, and why is it changing the way we handle register saves? Let’s break it down.