[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v2 09/10] hvm/hpet: Correctly limit period to a maximum.
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> --- xen/arch/x86/hvm/hpet.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/xen/arch/x86/hvm/hpet.c b/xen/arch/x86/hvm/hpet.c index 28f5224..3226a61 100644 --- a/xen/arch/x86/hvm/hpet.c +++ b/xen/arch/x86/hvm/hpet.c @@ -419,6 +419,9 @@ static int hpet_write( } else { + 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 @@ -427,7 +430,8 @@ 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; } } -- 1.8.4 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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