From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:55453) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZzjBF-0003jY-6o for qemu-devel@nongnu.org; Fri, 20 Nov 2015 05:44:40 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZzjBA-0006U4-IC for qemu-devel@nongnu.org; Fri, 20 Nov 2015 05:44:37 -0500 Received: from [59.151.112.132] (port=23679 helo=heian.cn.fujitsu.com) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZzjB9-0006Rc-KE for qemu-devel@nongnu.org; Fri, 20 Nov 2015 05:44:32 -0500 From: Cao jin Date: Fri, 20 Nov 2015 18:45:01 +0800 Message-ID: <1448016301-20944-1-git-send-email-caoj.fnst@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain Subject: [Qemu-devel] [PATCH] PCI: minor performance optimization List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: mst@redhat.com 1. Do param check in pci_add_capability2(), as it is a public API. 2. As spec says, each capability must be DWORD aligned, so an optimization can be done via Loop Unrolling. Signed-off-by: Cao jin --- hw/pci/pci.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/hw/pci/pci.c b/hw/pci/pci.c index 168b9cc..1e99603 100644 --- a/hw/pci/pci.c +++ b/hw/pci/pci.c @@ -1924,13 +1924,15 @@ PCIDevice *pci_create_simple(PCIBus *bus, int devfn, const char *name) static uint8_t pci_find_space(PCIDevice *pdev, uint8_t size) { int offset = PCI_CONFIG_HEADER_SIZE; - int i; - for (i = PCI_CONFIG_HEADER_SIZE; i < PCI_CONFIG_SPACE_SIZE; ++i) { + int i = PCI_CONFIG_HEADER_SIZE;; + + for (; i < PCI_CONFIG_SPACE_SIZE; i = i + 4) { if (pdev->used[i]) - offset = i + 1; - else if (i - offset + 1 == size) + offset = i + 4; + else if (i - offset >= size) return offset; } + return 0; } @@ -2144,6 +2146,8 @@ int pci_add_capability2(PCIDevice *pdev, uint8_t cap_id, uint8_t *config; int i, overlapping_cap; + assert(size > 0); + if (!offset) { offset = pci_find_space(pdev, size); if (!offset) { -- 2.1.0