14 DAY TRIAL // In response to a patch submitted by long-time Linux kernel developer and former Intel engineer David Woodhouse, Linus Torvalds ended up calling it "complete and utter garbage."
The patch submitted by David Woodhouse, ex-Intel kernel engineer that now works for Amazon described a so-called new feature for Intel processors to address Indirect Branch Restricted Speculation (IBRS) by creating macros that would restrict or unrestrict Indirect Branch Speculation based on if the Intel CPU will advertise "I am able to be not broken."
The "x86/enter: Create macros to restrict/unrestrict Indirect Branch Speculation" feature implies that the IBRS (Indirect Branch Restricted Speculation) bit needed to be set at boot time to "ask" the processor not to be broken. Linus Torvalds immediately reacted to the patch calling it "complete and utter garbage" despite the developer's efforts to explain why he implemented the nasty hack.
"All of this is pure garbage. Is Intel really planning on making this shit architectural?," says Linus Torvalds on the Linux kernel mailing list. "The whole point of having cpuid and flags from the microarchitecture is that we can use those to make decisions. But since we already know that the IBRS overhead is huge on existing hardware, all those hardware capability bits are just complete and utter garbage. Nobody sane will use them, since the cost is too damn high."
Linux kernel 4.15 delayed due to Meltdown and Spectre patches
The patches for the Meltdown and Spectre security vulnerabilities made a lot of Linux kernel developers nervous as they had to work overtime to push them into the mainline kernel over a short period of time. They need to redesign the kernel to address these critical issues that put billions of devices at risk of attacks. The industry is still working on patching Spectre, which is harder to fix than Meltdown.
Linux kernel 4.15 was even delayed twice because of the huge Meltdown and Spectre patches. Linus Torvalds released a rare RC9 Release Candidate over the weekend because he's exigent and wants everything to go well for Linux users. Linux kernel 4.15 will be the first kernel branch to ship with Spectre and Meltdown mitigations by default, and it's coming at the end of the week, on January 28, 2018.