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| author | Jan Kiszka <jan.kiszka@siemens.com> | 2011-09-12 14:10:22 +0200 |
|---|---|---|
| committer | Avi Kivity <avi@redhat.com> | 2011-09-25 19:52:44 +0300 |
| commit | 9bc5791d4aa78b72abd76f506c0a391a54abc4d1 (patch) | |
| tree | 40523d6fd982a91d8c9f1a0741085439d36e6143 | |
| parent | bd80158aff71a80292f96d9baea1a65bc0ce87b3 (diff) | |
| download | linux-stable-9bc5791d4aa78b72abd76f506c0a391a54abc4d1.tar.gz linux-stable-9bc5791d4aa78b72abd76f506c0a391a54abc4d1.tar.bz2 linux-stable-9bc5791d4aa78b72abd76f506c0a391a54abc4d1.zip | |
KVM: x86: Add module parameter for lapic periodic timer limit
Certain guests, specifically RTOSes, request faster periodic timers than
what we allow by default. Add a module parameter to adjust the limit for
non-standard setups. Also add a rate-limited warning in case the guest
requested more.
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
| -rw-r--r-- | arch/x86/kvm/lapic.c | 15 |
1 files changed, 13 insertions, 2 deletions
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index 4b53b811d1c1..2fb20caae5d8 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -68,6 +68,9 @@ #define VEC_POS(v) ((v) & (32 - 1)) #define REG_POS(v) (((v) >> 5) << 4) +static unsigned int min_timer_period_us = 500; +module_param(min_timer_period_us, uint, S_IRUGO | S_IWUSR); + static inline u32 apic_get_reg(struct kvm_lapic *apic, int reg_off) { return *((u32 *) (apic->regs + reg_off)); @@ -677,8 +680,16 @@ static void start_apic_timer(struct kvm_lapic *apic) * scheduler. */ if (apic_lvtt_period(apic)) { - if (apic->lapic_timer.period < NSEC_PER_MSEC/2) - apic->lapic_timer.period = NSEC_PER_MSEC/2; + s64 min_period = min_timer_period_us * 1000LL; + + if (apic->lapic_timer.period < min_period) { + pr_info_ratelimited( + "kvm: vcpu %i: requested %lld ns " + "lapic timer period limited to %lld ns\n", + apic->vcpu->vcpu_id, apic->lapic_timer.period, + min_period); + apic->lapic_timer.period = min_period; + } } hrtimer_start(&apic->lapic_timer.timer, |