Recently, a side-channel attack was discovered that exploits lazy FPU state switching to leak the contents of MMX, SSE, and AVX registers. The vulnerability can only be exploited when lazy FPU saves are used, as opposed to eager FPU saves. I am reading conflicting sources as to whether or not the Linux kernel is vulnerable. One source asserts that it is vulnerable. However, there is another resource from 2016 which explains that Linux uses eager FPU switching by default, indicating that it is unaffected. A commit from 2016 shows when eager switching became default.
Is Linux vulnerable, or is it not affected due to the use of eager FPU switching? My understanding is that it is vulnerable only if
eagerfpu=off, which is not the default. Is my understanding correct?