From patchwork Wed Feb 25 16:02:35 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Alex_Benn=C3=A9e?= X-Patchwork-Id: 5881301 Return-Path: X-Original-To: patchwork-kvm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 28BFF9F695 for ; Wed, 25 Feb 2015 16:02:56 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 5E4972010E for ; Wed, 25 Feb 2015 16:02:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 896B320383 for ; Wed, 25 Feb 2015 16:02:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753609AbbBYQCr (ORCPT ); Wed, 25 Feb 2015 11:02:47 -0500 Received: from static.88-198-71-155.clients.your-server.de ([88.198.71.155]:41190 "EHLO socrates.bennee.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753555AbbBYQCp (ORCPT ); Wed, 25 Feb 2015 11:02:45 -0500 Received: from localhost ([127.0.0.1] helo=zen.linaroharston) by socrates.bennee.com with esmtp (Exim 4.80) (envelope-from ) id 1YQfO9-0007hX-Sa; Wed, 25 Feb 2015 18:04:46 +0100 From: =?UTF-8?q?Alex=20Benn=C3=A9e?= To: qemu-devel@nongnu.org Cc: kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, christoffer.dall@linaro.org, marc.zyngier@arm.com, =?UTF-8?q?Alex=20Benn=C3=A9e?= Subject: [PATCH 3/6] hw/char/pl011: don't keep setting the IRQ if nothing changed Date: Wed, 25 Feb 2015 16:02:35 +0000 Message-Id: <1424880159-29348-4-git-send-email-alex.bennee@linaro.org> X-Mailer: git-send-email 2.3.0 In-Reply-To: <1424880159-29348-1-git-send-email-alex.bennee@linaro.org> References: <1424880159-29348-1-git-send-email-alex.bennee@linaro.org> MIME-Version: 1.0 X-SA-Exim-Connect-IP: 127.0.0.1 X-SA-Exim-Mail-From: alex.bennee@linaro.org X-SA-Exim-Scanned: No (on socrates.bennee.com); SAEximRunCond expanded to false Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP While observing KVM traces I can see additional IRQ calls on pretty much every MMIO access which is just plain inefficient. Only update the QEMU IRQ level if something has actually changed from last time. Otherwise we may be papering over other failure modes. Signed-off-by: Alex Bennée diff --git a/hw/char/pl011.c b/hw/char/pl011.c index 0a45115..bb554bc 100644 --- a/hw/char/pl011.c +++ b/hw/char/pl011.c @@ -36,6 +36,9 @@ typedef struct PL011State { CharDriverState *chr; qemu_irq irq; const unsigned char *id; + + /* not serialised, prevents pl011_update doing extra set_irqs */ + uint32_t current_irq; } PL011State; #define PL011_INT_TX 0x20 @@ -53,10 +56,11 @@ static const unsigned char pl011_id_luminary[8] = static void pl011_update(PL011State *s) { - uint32_t flags; - - flags = s->int_level & s->int_enabled; - qemu_set_irq(s->irq, flags != 0); + uint32_t flags = s->int_level & s->int_enabled; + if (flags != s->current_irq) { + s->current_irq = flags; + qemu_set_irq(s->irq, s->current_irq != 0); + } } static uint64_t pl011_read(void *opaque, hwaddr offset,