Sorry, forgot to CC +Tom Lendacky . Please take a look Tom, thanks.
On Wed, Nov 11, 2020 at 4:10 PM Joel Fernandes (Google) <[email protected]> wrote: > > Some hardware such as certain AMD variants don't have cross-HT MDS/L1TF > issues. Detect this and don't enable core scheduling as it can > needlessly slow the device done. > > Signed-off-by: Joel Fernandes (Google) <[email protected]> > --- > arch/x86/kernel/cpu/bugs.c | 8 ++++++++ > kernel/sched/core.c | 7 +++++++ > kernel/sched/sched.h | 5 +++++ > 3 files changed, 20 insertions(+) > > diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c > index dece79e4d1e9..0e6e61e49b23 100644 > --- a/arch/x86/kernel/cpu/bugs.c > +++ b/arch/x86/kernel/cpu/bugs.c > @@ -152,6 +152,14 @@ void __init check_bugs(void) > #endif > } > > +/* > + * Do not need core scheduling if CPU does not have MDS/L1TF vulnerability. > + */ > +int arch_allow_core_sched(void) > +{ > + return boot_cpu_has_bug(X86_BUG_MDS) || > boot_cpu_has_bug(X86_BUG_L1TF); > +} > + > void > x86_virt_spec_ctrl(u64 guest_spec_ctrl, u64 guest_virt_spec_ctrl, bool > setguest) > { > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 64c559192634..c6158b4959fe 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -319,6 +319,13 @@ static void __sched_core_enable(void) > for_each_online_cpu(cpu) > BUG_ON(!sched_core_empty(cpu_rq(cpu))); > > + /* > + * Some architectures may not want coresched. (ex, AMD does not have > + * MDS/L1TF issues so it wants SMT completely on). > + */ > + if (!arch_allow_core_sched()) > + return; > + > static_branch_enable(&__sched_core_enabled); > stop_machine(__sched_core_stopper, (void *)true, NULL); > > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h > index 3cf08c77b678..a1b39764a6ed 100644 > --- a/kernel/sched/sched.h > +++ b/kernel/sched/sched.h > @@ -1203,6 +1203,11 @@ int cpu_core_tag_color_write_u64(struct > cgroup_subsys_state *css, > > bool cfs_prio_less(struct task_struct *a, struct task_struct *b, bool fi); > > +int __weak arch_allow_core_sched(void) > +{ > + return true; > +} > + > #else /* !CONFIG_SCHED_CORE */ > > static inline bool sched_core_enqueued(struct task_struct *task) { return > false; } > -- > 2.29.2.222.g5d2a92d10f8-goog >
