diff options
Diffstat (limited to 'arch/x86/xen/time.c')
| -rw-r--r-- | arch/x86/xen/time.c | 72 |
1 files changed, 67 insertions, 5 deletions
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c index d9c945ee1100..96521b1874ac 100644 --- a/arch/x86/xen/time.c +++ b/arch/x86/xen/time.c @@ -20,6 +20,7 @@ #include <asm/pvclock.h> #include <asm/xen/hypervisor.h> #include <asm/xen/hypercall.h> +#include <asm/xen/cpuid.h> #include <xen/events.h> #include <xen/features.h> @@ -29,7 +30,7 @@ #include "xen-ops.h" /* Minimum amount of time until next clock event fires */ -#define TIMER_SLOP 100000 +#define TIMER_SLOP 1 static u64 xen_sched_clock_offset __read_mostly; @@ -60,9 +61,16 @@ static u64 xen_clocksource_get_cycles(struct clocksource *cs) return xen_clocksource_read(); } -static u64 xen_sched_clock(void) +static noinstr u64 xen_sched_clock(void) { - return xen_clocksource_read() - xen_sched_clock_offset; + struct pvclock_vcpu_time_info *src; + u64 ret; + + src = &__this_cpu_read(xen_vcpu)->time; + ret = pvclock_clocksource_read_nowd(src); + ret -= xen_sched_clock_offset; + + return ret; } static void xen_read_wallclock(struct timespec64 *ts) @@ -474,15 +482,47 @@ static void xen_setup_vsyscall_time_info(void) xen_clocksource.vdso_clock_mode = VDSO_CLOCKMODE_PVCLOCK; } +/* + * Check if it is possible to safely use the tsc as a clocksource. This is + * only true if the hypervisor notifies the guest that its tsc is invariant, + * the tsc is stable, and the tsc instruction will never be emulated. + */ +static int __init xen_tsc_safe_clocksource(void) +{ + u32 eax, ebx, ecx, edx; + + if (!(boot_cpu_has(X86_FEATURE_CONSTANT_TSC))) + return 0; + + if (!(boot_cpu_has(X86_FEATURE_NONSTOP_TSC))) + return 0; + + if (check_tsc_unstable()) + return 0; + + /* Leaf 4, sub-leaf 0 (0x40000x03) */ + cpuid_count(xen_cpuid_base() + 3, 0, &eax, &ebx, &ecx, &edx); + + return ebx == XEN_CPUID_TSC_MODE_NEVER_EMULATE; +} + static void __init xen_time_init(void) { struct pvclock_vcpu_time_info *pvti; int cpu = smp_processor_id(); struct timespec64 tp; - /* As Dom0 is never moved, no penalty on using TSC there */ + /* + * As Dom0 is never moved, no penalty on using TSC there. + * + * If it is possible for the guest to determine that the tsc is a safe + * clocksource, then set xen_clocksource rating below that of the tsc + * so that the system prefers tsc instead. + */ if (xen_initial_domain()) xen_clocksource.rating = 275; + else if (xen_tsc_safe_clocksource()) + xen_clocksource.rating = 299; clocksource_register_hz(&xen_clocksource, NSEC_PER_SEC); @@ -558,6 +598,11 @@ static void xen_hvm_setup_cpu_clockevents(void) void __init xen_hvm_init_time_ops(void) { + static bool hvm_time_initialized; + + if (hvm_time_initialized) + return; + /* * vector callback is needed otherwise we cannot receive interrupts * on cpu > 0 and at this point we don't know how many cpus are @@ -567,7 +612,22 @@ void __init xen_hvm_init_time_ops(void) return; if (!xen_feature(XENFEAT_hvm_safe_pvclock)) { - pr_info("Xen doesn't support pvclock on HVM, disable pv timer"); + pr_info_once("Xen doesn't support pvclock on HVM, disable pv timer"); + return; + } + + /* + * Only MAX_VIRT_CPUS 'vcpu_info' are embedded inside 'shared_info'. + * The __this_cpu_read(xen_vcpu) is still NULL when Xen HVM guest + * boots on vcpu >= MAX_VIRT_CPUS (e.g., kexec), To access + * __this_cpu_read(xen_vcpu) via xen_clocksource_read() will panic. + * + * The xen_hvm_init_time_ops() should be called again later after + * __this_cpu_read(xen_vcpu) is available. + */ + if (!__this_cpu_read(xen_vcpu)) { + pr_info("Delay xen_init_time_common() as kernel is running on vcpu=%d\n", + xen_vcpu_nr(0)); return; } @@ -577,6 +637,8 @@ void __init xen_hvm_init_time_ops(void) x86_cpuinit.setup_percpu_clockev = xen_hvm_setup_cpu_clockevents; x86_platform.set_wallclock = xen_set_wallclock; + + hvm_time_initialized = true; } #endif |