On Fri, Apr 09, 2021 at 01:22:49PM -0500, Saripalli, RK wrote: > > And I think you don't need this one either if we do a "light" controls > > thing but lemme look at the rest first.
Ok, and what I mean with "lite" version is something like this below which needs finishing and testing. Initially, it could support the cmdline params: predict_store_fwd={on,off,auto} to give people the opportunity to experiment with the feature. If it turns out that prctl and seccomp per-task toggling is needed then sure, we can extend but I don't see the reason for a whole separate set of options yet. Especially is ssbd already controls this. AFAICT, of course and if I'm not missing some other aspect here. Thx. --- diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c index 2d11384dc9ab..226b73700f88 100644 --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -1165,3 +1165,22 @@ void set_dr_addr_mask(unsigned long mask, int dr) break; } } + +static int __init psf_cmdline(char *str) +{ + if (!boot_cpu_has(X86_FEATURE_PSFD)) + return 0; + + if (!str) + return -EINVAL; + + if (!strcmp(str, "off")) { + x86_spec_ctrl_base |= SPEC_CTRL_PSFD; + setup_clear_cpu_cap(X86_FEATURE_PSFD); + } + + return 0; +} +early_param("predict_store_fwd", psf_cmdline); + + -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette