| Message ID | 20250106124633.1418972-12-nikunj@amd.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Add Secure TSC support for SNP guests | expand |
On Mon, Jan 06, 2025 at 06:16:31PM +0530, Nikunj A Dadhania wrote: > Hypervisor platform setup (x86_hyper_init::init_platform) routines register > their own PV clock sources (KVM, HyperV, and Xen) at different clock > ratings, resulting in PV clocksource being selected even when a stable TSC > clocksource is available. Upgrade the clock rating of the TSC early and > regular clocksource to prefer TSC over PV clock sources when TSC is > invariant, non-stop, and stable > > Cc: Alexey Makhalov <alexey.makhalov@broadcom.com> > Cc: Juergen Gross <jgross@suse.com> > Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> > Suggested-by: Thomas Gleixner <tglx@linutronix.de> > Signed-off-by: Nikunj A Dadhania <nikunj@amd.com> > --- > arch/x86/kernel/tsc.c | 21 +++++++++++++++++++++ > 1 file changed, 21 insertions(+) This needs to make it perfectly clear that it is about virt and not in general: diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index e98b7e585c1c..3741d097d925 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -276,14 +276,16 @@ bool using_native_sched_clock(void) /* * Upgrade the clock rating for TSC early and regular clocksource when the - * underlying platform provides non-stop, invariant, and stable TSC. TSC + * underlying guest is provided a non-stop, invariant, and stable TSC. TSC * early/regular clocksource will be preferred over other PV clock sources. */ -static void __init upgrade_clock_rating(struct clocksource *tsc_early, - struct clocksource *tsc) +static void __init virt_upgrade_clock_rating(struct clocksource *tsc_early, + struct clocksource *tsc) { - if (cpu_feature_enabled(X86_FEATURE_HYPERVISOR) && - cpu_feature_enabled(X86_FEATURE_CONSTANT_TSC) && + if (!cpu_feature_enabled(X86_FEATURE_HYPERVISOR)) + return; + + if (cpu_feature_enabled(X86_FEATURE_CONSTANT_TSC) && cpu_feature_enabled(X86_FEATURE_NONSTOP_TSC) && !tsc_unstable) { tsc_early->rating = 449; @@ -295,7 +297,7 @@ u64 sched_clock_noinstr(void) __attribute__((alias("native_sched_clock"))); bool using_native_sched_clock(void) { return true; } -static void __init upgrade_clock_rating(struct clocksource *tsc_early, struct clocksource *tsc) { } +static void __init virt_upgrade_clock_rating(struct clocksource *tsc_early, struct clocksource *tsc) { } #endif notrace u64 sched_clock(void) @@ -1584,7 +1586,7 @@ void __init tsc_init(void) if (tsc_clocksource_reliable || no_tsc_watchdog) tsc_disable_clocksource_watchdog(); - upgrade_clock_rating(&clocksource_tsc_early, &clocksource_tsc); + virt_upgrade_clock_rating(&clocksource_tsc_early, &clocksource_tsc); clocksource_register_khz(&clocksource_tsc_early, tsc_khz); detect_art();
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 34dec0b72ea8..88d8bfceea04 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -274,10 +274,29 @@ bool using_native_sched_clock(void) { return static_call_query(pv_sched_clock) == native_sched_clock; } + +/* + * Upgrade the clock rating for TSC early and regular clocksource when the + * underlying platform provides non-stop, invariant, and stable TSC. TSC + * early/regular clocksource will be preferred over other PV clock sources. + */ +static void __init upgrade_clock_rating(struct clocksource *tsc_early, + struct clocksource *tsc) +{ + if (cpu_feature_enabled(X86_FEATURE_HYPERVISOR) && + cpu_feature_enabled(X86_FEATURE_CONSTANT_TSC) && + cpu_feature_enabled(X86_FEATURE_NONSTOP_TSC) && + !tsc_unstable) { + tsc_early->rating = 449; + tsc->rating = 450; + } +} #else u64 sched_clock_noinstr(void) __attribute__((alias("native_sched_clock"))); bool using_native_sched_clock(void) { return true; } + +static void __init upgrade_clock_rating(struct clocksource *tsc_early, struct clocksource *tsc) { } #endif notrace u64 sched_clock(void) @@ -1564,6 +1583,8 @@ void __init tsc_init(void) if (tsc_clocksource_reliable || no_tsc_watchdog) tsc_disable_clocksource_watchdog(); + upgrade_clock_rating(&clocksource_tsc_early, &clocksource_tsc); + clocksource_register_khz(&clocksource_tsc_early, tsc_khz); detect_art(); }
Hypervisor platform setup (x86_hyper_init::init_platform) routines register their own PV clock sources (KVM, HyperV, and Xen) at different clock ratings, resulting in PV clocksource being selected even when a stable TSC clocksource is available. Upgrade the clock rating of the TSC early and regular clocksource to prefer TSC over PV clock sources when TSC is invariant, non-stop, and stable Cc: Alexey Makhalov <alexey.makhalov@broadcom.com> Cc: Juergen Gross <jgross@suse.com> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Nikunj A Dadhania <nikunj@amd.com> --- arch/x86/kernel/tsc.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+)