On 29/7/20 11:14 pm, Tom Lendacky wrote: > > > On 7/28/20 7:11 PM, Balbir Singh wrote: >> Use the existing PR_GET/SET_SPECULATION_CTRL API to expose the L1D >> flush capability. For L1D flushing PR_SPEC_FORCE_DISABLE and >> PR_SPEC_DISABLE_NOEXEC are not supported. >> >> There is also no seccomp integration for the feature. >> >> Signed-off-by: Balbir Singh <[email protected]> >> --- >> arch/x86/kernel/cpu/bugs.c | 54 ++++++++++++++++++++++++++++++++++++++ >> arch/x86/mm/tlb.c | 25 +++++++++++++++++- >> include/uapi/linux/prctl.h | 1 + >> 3 files changed, 79 insertions(+), 1 deletion(-) >> >> diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c >> index 0b71970d2d3d..935ea88313ab 100644 >> --- a/arch/x86/kernel/cpu/bugs.c >> +++ b/arch/x86/kernel/cpu/bugs.c >> @@ -295,6 +295,13 @@ enum taa_mitigations { >> TAA_MITIGATION_TSX_DISABLED, >> }; >> >> +enum l1d_flush_out_mitigations { >> + L1D_FLUSH_OUT_OFF, >> + L1D_FLUSH_OUT_ON, >> +}; >> + >> +static enum l1d_flush_out_mitigations l1d_flush_out_mitigation >> __ro_after_init = L1D_FLUSH_OUT_ON; >> + >> /* Default mitigation for TAA-affected CPUs */ >> static enum taa_mitigations taa_mitigation __ro_after_init = >> TAA_MITIGATION_VERW; >> static bool taa_nosmt __ro_after_init; >> @@ -378,6 +385,18 @@ static void __init taa_select_mitigation(void) >> pr_info("%s\n", taa_strings[taa_mitigation]); >> } >> >> +static int __init l1d_flush_out_parse_cmdline(char *str) >> +{ >> + if (!boot_cpu_has_bug(X86_BUG_L1TF)) >> + return 0; > > Shouldn't this set the l1d_flush_out_mitigation to L1D_FLUSH_OUT_OFF since > it is set to L1D_FLUSH_OUT_ON by default? Or does it not matter because > the enable_l1d_flush_for_task() will return -EINVAL if the cpu doesn't > have the L1TF bug? > > I guess it depends on what you want l1d_flush_out_prctl_set() and > l1d_flush_out_prctl_get() to return in this case. >
Exactly! We want to differentiate between force disabled and not applicable. Thanks for the review, Balbir Singh.
