Re: [PATCH for-4.14] x86/spec-ctrl: Protect against CALL/JMP straight-line speculation

[Jan Beulich <jbeulich@xxxxxxxx>]

On 01.07.2020 13:58, Andrew Cooper wrote:
> Some x86 CPUs speculatively execute beyond indirect CALL/JMP instructions.
> 
> With CONFIG_INDIRECT_THUNK / Retpolines, indirect CALL/JMP instructions are
> converted to direct CALL/JMP's to __x86_indirect_thunk_REG(), leaving just a
> handful of indirect JMPs implementing those stubs.
> 
> There is no architectrual execution beyond an indirect JMP, so use INT3 as
> recommended by vendors to halt speculative execution.  This is shorter than
> LFENCE (which would also work fine), but also shows up in logs if we do
> unexpected execute them.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>