From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34601) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ajMPF-0007zF-Vd for qemu-devel@nongnu.org; Fri, 25 Mar 2016 03:44:30 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ajMO5-0005G2-1X for qemu-devel@nongnu.org; Fri, 25 Mar 2016 03:43:41 -0400 Received: from mx1.redhat.com ([209.132.183.28]:40246) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ajMO4-0005Fy-QN for qemu-devel@nongnu.org; Fri, 25 Mar 2016 03:42:28 -0400 From: Jason Wang Date: Fri, 25 Mar 2016 15:42:08 +0800 Message-Id: <1458891729-28131-7-git-send-email-jasowang@redhat.com> In-Reply-To: <1458891729-28131-1-git-send-email-jasowang@redhat.com> References: <1458891729-28131-1-git-send-email-jasowang@redhat.com> Subject: [Qemu-devel] [PULL 6/7] e1000: Fixing interrupts pace. List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: peter.maydell@linaro.org, qemu-devel@nongnu.org Cc: Jason Wang , Sameeh Jubran From: Sameeh Jubran This patch introduces an upper bound for number of interrupts per second. Without this bound an interrupt storm can occur as it has been observed on Windows 10 when disabling the device. According to the SPEC - Intel PCI/PCI-X Family of Gigabit Ethernet Controllers Software Developer's Manual, section 13.4.18 - the Ethernet controller guarantees a maximum observable interrupt rate of 7813 interrupts/sec. If there is no upper bound this could lead to an interrupt storm by e1000 (when mit_delay < 500) causing interrupts to fire at a very high pace. Thus if mit_delay < 500 then the delay should be set to the minimum delay possible which is 500. This can be calculated easily as follows: Interval = 10^9 / (7813 * 256) = 500. Signed-off-by: Sameeh Jubran Signed-off-by: Jason Wang --- hw/net/e1000.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/hw/net/e1000.c b/hw/net/e1000.c index 0387fa0..09b9ab5 100644 --- a/hw/net/e1000.c +++ b/hw/net/e1000.c @@ -357,6 +357,14 @@ set_interrupt_cause(E1000State *s, int index, uint32_t val) } mit_update_delay(&mit_delay, s->mac_reg[ITR]); + /* + * According to e1000 SPEC, the Ethernet controller guarantees + * a maximum observable interrupt rate of 7813 interrupts/sec. + * Thus if mit_delay < 500 then the delay should be set to the + * minimum delay possible which is 500. + */ + mit_delay = (mit_delay < 500) ? 500 : mit_delay; + if (mit_delay) { s->mit_timer_on = 1; timer_mod(s->mit_timer, qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + -- 2.5.0