Later commits will cause objtool to warn about static keys being used in .noinstr sections in order to safely defer instruction patching IPIs targeted at NOHZ_FULL CPUs.
The VMX keys are used in .noinstr code, and can be modified at runtime (/proc/kernel/vmx* write). However it is not expected that they will be flipped during latency-sensitive operations, and thus shouldn't be a source of interference for NOHZ_FULL CPUs wrt the text patching IPI. Note, smp_text_poke_batch_finish() never defers IPIs if noinstr code is being patched, i.e. this is purely to tell objtool we're okay with updates to that key causing IPIs and to silence the associated objtool warning. Reported-by: Josh Poimboeuf <[email protected]> Signed-off-by: Valentin Schneider <[email protected]> Acked-by: Sean Christopherson <[email protected]> --- arch/x86/kvm/vmx/vmx.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 91b6f2f3edc2a..99936a2af6641 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -203,8 +203,15 @@ module_param(pt_mode, int, S_IRUGO); struct x86_pmu_lbr __ro_after_init vmx_lbr_caps; -static DEFINE_STATIC_KEY_FALSE(vmx_l1d_should_flush); -static DEFINE_STATIC_KEY_FALSE(vmx_l1d_flush_cond); +/* + * NOINSTR: Both of these static keys end up being used in .noinstr sections, + * however they are only modified: + * - at init + * - from a /proc/kernel/vmx* write + * thus during latency-sensitive operations they should remain stable. + */ +static DEFINE_STATIC_KEY_FALSE_NOINSTR(vmx_l1d_should_flush); +static DEFINE_STATIC_KEY_FALSE_NOINSTR(vmx_l1d_flush_cond); static DEFINE_MUTEX(vmx_l1d_flush_mutex); /* Storage for pre module init parameter parsing */ -- 2.51.0
