Add a return code to __paravirt_set_sched_clock() so that the kernel can reject attempts to use a PV sched_clock without breaking the caller. E.g. when running as a CoCo VM with a secure TSC, using a PV clock is generally undesirable.
Note, kvmclock is the only PV clock that does anything "extra" beyond simply registering itself as sched_clock, i.e. is the only caller that needs to check the new return value. Signed-off-by: Sean Christopherson <[email protected]> --- arch/x86/include/asm/timer.h | 6 +++--- arch/x86/kernel/kvmclock.c | 8 +++++--- arch/x86/kernel/tsc.c | 5 +++-- 3 files changed, 11 insertions(+), 8 deletions(-) diff --git a/arch/x86/include/asm/timer.h b/arch/x86/include/asm/timer.h index 96ae7feac47c..ca5c95d48c03 100644 --- a/arch/x86/include/asm/timer.h +++ b/arch/x86/include/asm/timer.h @@ -14,14 +14,14 @@ extern int no_timer_check; extern bool using_native_sched_clock(void); #ifdef CONFIG_PARAVIRT -void __init __paravirt_set_sched_clock(u64 (*func)(void), bool stable, - void (*save)(void), void (*restore)(void)); +int __init __paravirt_set_sched_clock(u64 (*func)(void), bool stable, + void (*save)(void), void (*restore)(void)); static __always_inline void paravirt_set_sched_clock(u64 (*func)(void), void (*save)(void), void (*restore)(void)) { - __paravirt_set_sched_clock(func, true, save, restore); + (void)__paravirt_set_sched_clock(func, true, save, restore); } #endif diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c index d3bb281c0805..9b3d1ed1a96d 100644 --- a/arch/x86/kernel/kvmclock.c +++ b/arch/x86/kernel/kvmclock.c @@ -338,10 +338,12 @@ static int kvmclock_setup_percpu(unsigned int cpu) static __init void kvm_sched_clock_init(bool stable) { + if (__paravirt_set_sched_clock(kvm_sched_clock_read, stable, + kvm_save_sched_clock_state, + kvm_restore_sched_clock_state)) + return; + kvm_sched_clock_offset = kvm_clock_read(); - __paravirt_set_sched_clock(kvm_sched_clock_read, stable, - kvm_save_sched_clock_state, - kvm_restore_sched_clock_state); kvmclock_is_sched_clock = true; /* diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 4a48b8ba5bea..3c15fc10e501 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -280,8 +280,8 @@ bool using_native_sched_clock(void) return static_call_query(pv_sched_clock) == native_sched_clock; } -void __init __paravirt_set_sched_clock(u64 (*func)(void), bool stable, - void (*save)(void), void (*restore)(void)) +int __init __paravirt_set_sched_clock(u64 (*func)(void), bool stable, + void (*save)(void), void (*restore)(void)) { if (!stable) clear_sched_clock_stable(); @@ -289,6 +289,7 @@ void __init __paravirt_set_sched_clock(u64 (*func)(void), bool stable, static_call_update(pv_sched_clock, func); x86_platform.save_sched_clock_state = save; x86_platform.restore_sched_clock_state = restore; + return 0; } #else u64 sched_clock_noinstr(void) __attribute__((alias("native_sched_clock"))); -- 2.54.0.563.g4f69b47b94-goog
