From 7941e39b295fe3ea56a7157a014c596af5af5d86 Mon Sep 17 00:00:00 2001 From: Keir Fraser Date: Thu, 10 Jan 2008 11:39:23 +0000 Subject: [PATCH] hvm: hpet: Fix overflow when converting to nanoseconds. Currently in hpet_tick_to_ns, the approach is multiplying first, which easily causes overflow when tick is quite large. The patch cannot handle arbitratry large ticks duo to the precision requirement and 64bit's value range. But by optimize the equation, a larger ticks than current code can be supported. Also an overflow check is added before the calculation. From: Haitao Shan Signed-off-by: Keir Fraser xen-unstable changeset: 16693:9ff64d045e61e7db6844b3db473e660e8c7e0551 xen-unstable date: Tue Jan 08 16:20:04 2008 +0000 --- xen/arch/x86/hvm/hpet.c | 8 ++++++-- xen/include/asm-x86/hvm/vpt.h | 2 ++ 2 files changed, 8 insertions(+), 2 deletions(-) diff --git a/xen/arch/x86/hvm/hpet.c b/xen/arch/x86/hvm/hpet.c index a4a2cd0d3..9e2527090 100644 --- a/xen/arch/x86/hvm/hpet.c +++ b/xen/arch/x86/hvm/hpet.c @@ -71,8 +71,9 @@ #define HPET_TN_INT_ROUTE_CAP_MASK (0xffffffffULL \ << HPET_TN_INT_ROUTE_CAP_SHIFT) -#define hpet_tick_to_ns(h, tick) ((s_time_t)(tick)* \ - (S_TO_NS*TSC_PER_HPET_TICK)/h->tsc_freq) +#define hpet_tick_to_ns(h, tick) \ + ((s_time_t)((((tick) > (h)->hpet_to_ns_limit) ? \ + ~0ULL : (tick) * (h)->hpet_to_ns_scale) >> 10)) #define timer_config(h, n) (h->hpet.timers[n].config) #define timer_is_periodic(h, n) (timer_config(h, n) & HPET_TN_PERIODIC) @@ -465,6 +466,9 @@ void hpet_init(struct vcpu *v) h->vcpu = v; h->tsc_freq = ticks_per_sec(v); + h->hpet_to_ns_scale = ((S_TO_NS * TSC_PER_HPET_TICK) << 10) / h->tsc_freq; + h->hpet_to_ns_limit = (~0ULL >> 1) / h->hpet_to_ns_scale; + /* 64-bit main counter; 3 timers supported; LegacyReplacementRoute. */ h->hpet.capability = 0x8086A201ULL; diff --git a/xen/include/asm-x86/hvm/vpt.h b/xen/include/asm-x86/hvm/vpt.h index 38d4aae9e..1991f3f7b 100644 --- a/xen/include/asm-x86/hvm/vpt.h +++ b/xen/include/asm-x86/hvm/vpt.h @@ -41,6 +41,8 @@ typedef struct HPETState { struct hvm_hw_hpet hpet; struct vcpu *vcpu; uint64_t tsc_freq; + uint64_t hpet_to_ns_scale; /* hpet ticks to ns (multiplied by 2^10) */ + uint64_t hpet_to_ns_limit; /* max hpet ticks convertable to ns */ uint64_t mc_offset; struct timer timers[HPET_TIMER_NUM]; struct HPET_timer_fn_info timer_fn_info[HPET_TIMER_NUM]; -- 2.39.5