From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:38936) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fXQ4F-0007QQ-D0 for qemu-devel@nongnu.org; Mon, 25 Jun 2018 07:54:00 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fXQ4C-0001bt-UT for qemu-devel@nongnu.org; Mon, 25 Jun 2018 07:53:59 -0400 From: David Hildenbrand Date: Mon, 25 Jun 2018 13:53:44 +0200 Message-Id: <20180625115352.6889-2-david@redhat.com> In-Reply-To: <20180625115352.6889-1-david@redhat.com> References: <20180625115352.6889-1-david@redhat.com> Subject: [Qemu-devel] [PATCH v3 1/9] s390x/tcg: avoid overflows in time2tod/tod2time List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-s390x@nongnu.org Cc: qemu-devel@nongnu.org, Richard Henderson , Alexander Graf , Cornelia Huck , Christian Borntraeger , Thomas Huth , David Hildenbrand Big values for the TOD/ns clock can result in some overflows that can be avoided. Not all overflows can be handled however, as the conversion either multiplies by 4.096 or divided by 4.096. Apply the trick used in the Linux kernel in arch/s390/include/asm/timex.h for tod_to_ns() and use the same trick also for the conversion in the other direction. Signed-off-by: David Hildenbrand --- target/s390x/internal.h | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/target/s390x/internal.h b/target/s390x/internal.h index e392a02d12..6cf63340bf 100644 --- a/target/s390x/internal.h +++ b/target/s390x/internal.h @@ -243,13 +243,14 @@ enum cc_op { /* Converts ns to s390's clock format */ static inline uint64_t time2tod(uint64_t ns) { - return (ns << 9) / 125; + return (ns << 9) / 125 + (((ns & 0xff10000000000000ull) / 125) << 9); + } /* Converts s390's clock format to ns */ static inline uint64_t tod2time(uint64_t t) { - return (t * 125) >> 9; + return ((t >> 9) * 125) + (((t & 0x1ff) * 125) >> 9); } static inline hwaddr decode_basedisp_s(CPUS390XState *env, uint32_t ipb, -- 2.17.1