3.2.56-rc1 review patch. If anyone has any objections, please let me know.
------------------ From: Marcelo Tosatti <[email protected]> commit 9ed96e87c5748de4c2807ef17e81287c7304186c upstream. Limit PIT timer frequency similarly to the limit applied by LAPIC timer. Reviewed-by: Jan Kiszka <[email protected]> Signed-off-by: Marcelo Tosatti <[email protected]> Signed-off-by: Paolo Bonzini <[email protected]> [bwh: Backported to 3.2: - Adjust context - s/ps->period/pt->period/] Signed-off-by: Ben Hutchings <[email protected]> --- arch/x86/kvm/i8254.c | 18 ++++++++++++++++++ arch/x86/kvm/lapic.c | 3 --- arch/x86/kvm/x86.c | 3 +++ arch/x86/kvm/x86.h | 2 ++ 4 files changed, 23 insertions(+), 3 deletions(-) --- a/arch/x86/kvm/i8254.c +++ b/arch/x86/kvm/i8254.c @@ -38,6 +38,7 @@ #include "irq.h" #include "i8254.h" +#include "x86.h" #ifndef CONFIG_X86_64 #define mod_64(x, y) ((x) - (y) * div64_u64(x, y)) @@ -364,6 +365,23 @@ static void create_pit_timer(struct kvm atomic_set(&pt->pending, 0); ps->irq_ack = 1; + /* + * Do not allow the guest to program periodic timers with small + * interval, since the hrtimers are not throttled by the host + * scheduler. + */ + if (ps->is_periodic) { + s64 min_period = min_timer_period_us * 1000LL; + + if (pt->period < min_period) { + pr_info_ratelimited( + "kvm: requested %lld ns " + "i8254 timer period limited to %lld ns\n", + pt->period, min_period); + pt->period = min_period; + } + } + hrtimer_start(&pt->timer, ktime_add_ns(ktime_get(), interval), HRTIMER_MODE_ABS); } --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -68,9 +68,6 @@ #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)); --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -92,6 +92,9 @@ EXPORT_SYMBOL_GPL(kvm_x86_ops); int ignore_msrs = 0; module_param_named(ignore_msrs, ignore_msrs, bool, S_IRUGO | S_IWUSR); +unsigned int min_timer_period_us = 500; +module_param(min_timer_period_us, uint, S_IRUGO | S_IWUSR); + bool kvm_has_tsc_control; EXPORT_SYMBOL_GPL(kvm_has_tsc_control); u32 kvm_max_guest_tsc_khz; --- a/arch/x86/kvm/x86.h +++ b/arch/x86/kvm/x86.h @@ -125,4 +125,6 @@ int kvm_write_guest_virt_system(struct x gva_t addr, void *val, unsigned int bytes, struct x86_exception *exception); +extern unsigned int min_timer_period_us; + #endif -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
