[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v3 04/11] hvm/hpet: Correctly limit period to a maximum.
>>> On 17.04.14 at 19:42, <dslutz@xxxxxxxxxxx> wrote: > In the code section after the comment: > > /* > * Clamp period to reasonable min/max values: > * - minimum is 100us, same as timers controlled by vpt.c > * - maximum is to prevent overflow in time_after() calculations > */ > > The current maximum limit actually allows "bad" values like 0 and 1. > This is because it uses a mask not a maximum. > > Signed-off-by: Don Slutz <dslutz@xxxxxxxxxxx> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx> > xen/arch/x86/hvm/hpet.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/xen/arch/x86/hvm/hpet.c b/xen/arch/x86/hvm/hpet.c > index 910d87d..c64c547 100644 > --- a/xen/arch/x86/hvm/hpet.c > +++ b/xen/arch/x86/hvm/hpet.c > @@ -404,6 +404,8 @@ static int hpet_write( > if ( timer_is_periodic(h, tn) && > !(h->hpet.timers[tn].config & HPET_TN_SETVAL) ) > { > + uint64_t max_period = (timer_is_32bit(h, tn) ? ~0u : ~0ull) >> 1; > + > /* > * Clamp period to reasonable min/max values: > * - minimum is 100us, same as timers controlled by vpt.c > @@ -411,7 +413,8 @@ static int hpet_write( > */ > if ( hpet_tick_to_ns(h, new_val) < MICROSECS(100) ) > new_val = (MICROSECS(100) << 10) / h->hpet_to_ns_scale; > - new_val &= (timer_is_32bit(h, tn) ? ~0u : ~0ull) >> 1; > + if ( new_val > max_period ) > + new_val = max_period; > h->hpet.period[tn] = new_val; > } > else > -- > 1.8.4 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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