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Linux kernel developer here. I don’t know know how MS’s Meltdown solution differs from Linux’s, let alone whether I should hate it.

MS (I think) uses IBRS to help with Spectre, and IBRS is not so great. Retpolines have a more fun name at the very least :)

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I think he means Linux kernel developers hate (their own) solution for Meltdown.

The essential element of the solution for Meltdown is the same in every x86-64 OS: unmapping the kernel when in usermode. This is widely hated because it makes kernel entries and exits much slower, and blows away the TLB if your hardware doesn't have PCID support.

Yes, this.

It sucks, but what else can one do?

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