On Tue, May 22, 2018 at 04:06:43PM +0100, Marc Zyngier wrote: > In order to allow userspace to be mitigated on demand, let's > introduce a new thread flag that prevents the mitigation from > being turned off when exiting to userspace, and doesn't turn > it on on entry into the kernel (with the assumtion that the Nit: s/assumtion/assumption/ > mitigation is always enabled in the kernel itself). > > This will be used by a prctl interface introduced in a later > patch. > > Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx> On the assumption that this flag cannot be flipped while a task is in userspace: Reviewed-by: Mark Rutland <mark.rutland@xxxxxxx> Mark. > --- > arch/arm64/include/asm/thread_info.h | 1 + > arch/arm64/kernel/entry.S | 2 ++ > 2 files changed, 3 insertions(+) > > diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h > index 740aa03c5f0d..cbcf11b5e637 100644 > --- a/arch/arm64/include/asm/thread_info.h > +++ b/arch/arm64/include/asm/thread_info.h > @@ -94,6 +94,7 @@ void arch_release_task_struct(struct task_struct *tsk); > #define TIF_32BIT 22 /* 32bit process */ > #define TIF_SVE 23 /* Scalable Vector Extension in use */ > #define TIF_SVE_VL_INHERIT 24 /* Inherit sve_vl_onexec across exec */ > +#define TIF_SSBD 25 /* Wants SSB mitigation */ > > #define _TIF_SIGPENDING (1 << TIF_SIGPENDING) > #define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED) > diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S > index e6f6e2339b22..28ad8799406f 100644 > --- a/arch/arm64/kernel/entry.S > +++ b/arch/arm64/kernel/entry.S > @@ -147,6 +147,8 @@ alternative_cb arm64_enable_wa2_handling > alternative_cb_end > ldr_this_cpu \tmp2, arm64_ssbd_callback_required, \tmp1 > cbz \tmp2, \targ > + ldr \tmp2, [tsk, #TSK_TI_FLAGS] > + tbnz \tmp2, #TIF_SSBD, \targ > mov w0, #ARM_SMCCC_ARCH_WORKAROUND_2 > mov w1, #\state > alternative_cb arm64_update_smccc_conduit > -- > 2.14.2 > > _______________________________________________ > kvmarm mailing list > kvmarm@xxxxxxxxxxxxxxxxxxxxx > https://lists.cs.columbia.edu/mailman/listinfo/kvmarm _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
