From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3945EC8300C for ; Tue, 17 Nov 2020 13:50:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DD680221F8 for ; Tue, 17 Nov 2020 13:50:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="aBgzPuNf" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732264AbgKQNcU (ORCPT ); Tue, 17 Nov 2020 08:32:20 -0500 Received: from mail.kernel.org ([198.145.29.99]:41218 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731609AbgKQNbu (ORCPT ); Tue, 17 Nov 2020 08:31:50 -0500 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 36A0D207BC; Tue, 17 Nov 2020 13:31:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1605619908; bh=Mt69135e1oi6Zy6gjvQ/+941SEt9u4XvZhiHgz0TAtY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=aBgzPuNfNKWTt6kS88V+y/SYKtUynxyK3QB7eXxzVzjGy2779ywu7LEEg0miYGoW/ zkldwqpNFPjlkTZ40sWa9mHhbygGf4nKmm6WpBTDyAvGEeSuGTjizTwihu9pusYqrI AbmPiYbdm1aqvCOUD+t7s8wAN+ezwhEjMPIQEtek= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Ian Pilcher , Justin Gatzen , Alex Williamson , Sasha Levin Subject: [PATCH 5.9 044/255] vfio/pci: Implement ioeventfd thread handler for contended memory lock Date: Tue, 17 Nov 2020 14:03:04 +0100 Message-Id: <20201117122141.095356131@linuxfoundation.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201117122138.925150709@linuxfoundation.org> References: <20201117122138.925150709@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Alex Williamson [ Upstream commit 38565c93c8a1306dc5f245572a545fbea908ac41 ] The ioeventfd is called under spinlock with interrupts disabled, therefore if the memory lock is contended defer code that might sleep to a thread context. Fixes: bc93b9ae0151 ("vfio-pci: Avoid recursive read-lock usage") Link: https://bugzilla.kernel.org/show_bug.cgi?id=209253#c1 Reported-by: Ian Pilcher Tested-by: Ian Pilcher Tested-by: Justin Gatzen Signed-off-by: Alex Williamson Signed-off-by: Sasha Levin --- drivers/vfio/pci/vfio_pci_rdwr.c | 43 ++++++++++++++++++++++++++------ 1 file changed, 35 insertions(+), 8 deletions(-) diff --git a/drivers/vfio/pci/vfio_pci_rdwr.c b/drivers/vfio/pci/vfio_pci_rdwr.c index 9e353c484ace2..a0b5fc8e46f4d 100644 --- a/drivers/vfio/pci/vfio_pci_rdwr.c +++ b/drivers/vfio/pci/vfio_pci_rdwr.c @@ -356,34 +356,60 @@ ssize_t vfio_pci_vga_rw(struct vfio_pci_device *vdev, char __user *buf, return done; } -static int vfio_pci_ioeventfd_handler(void *opaque, void *unused) +static void vfio_pci_ioeventfd_do_write(struct vfio_pci_ioeventfd *ioeventfd, + bool test_mem) { - struct vfio_pci_ioeventfd *ioeventfd = opaque; - switch (ioeventfd->count) { case 1: - vfio_pci_iowrite8(ioeventfd->vdev, ioeventfd->test_mem, + vfio_pci_iowrite8(ioeventfd->vdev, test_mem, ioeventfd->data, ioeventfd->addr); break; case 2: - vfio_pci_iowrite16(ioeventfd->vdev, ioeventfd->test_mem, + vfio_pci_iowrite16(ioeventfd->vdev, test_mem, ioeventfd->data, ioeventfd->addr); break; case 4: - vfio_pci_iowrite32(ioeventfd->vdev, ioeventfd->test_mem, + vfio_pci_iowrite32(ioeventfd->vdev, test_mem, ioeventfd->data, ioeventfd->addr); break; #ifdef iowrite64 case 8: - vfio_pci_iowrite64(ioeventfd->vdev, ioeventfd->test_mem, + vfio_pci_iowrite64(ioeventfd->vdev, test_mem, ioeventfd->data, ioeventfd->addr); break; #endif } +} + +static int vfio_pci_ioeventfd_handler(void *opaque, void *unused) +{ + struct vfio_pci_ioeventfd *ioeventfd = opaque; + struct vfio_pci_device *vdev = ioeventfd->vdev; + + if (ioeventfd->test_mem) { + if (!down_read_trylock(&vdev->memory_lock)) + return 1; /* Lock contended, use thread */ + if (!__vfio_pci_memory_enabled(vdev)) { + up_read(&vdev->memory_lock); + return 0; + } + } + + vfio_pci_ioeventfd_do_write(ioeventfd, false); + + if (ioeventfd->test_mem) + up_read(&vdev->memory_lock); return 0; } +static void vfio_pci_ioeventfd_thread(void *opaque, void *unused) +{ + struct vfio_pci_ioeventfd *ioeventfd = opaque; + + vfio_pci_ioeventfd_do_write(ioeventfd, ioeventfd->test_mem); +} + long vfio_pci_ioeventfd(struct vfio_pci_device *vdev, loff_t offset, uint64_t data, int count, int fd) { @@ -457,7 +483,8 @@ long vfio_pci_ioeventfd(struct vfio_pci_device *vdev, loff_t offset, ioeventfd->test_mem = vdev->pdev->resource[bar].flags & IORESOURCE_MEM; ret = vfio_virqfd_enable(ioeventfd, vfio_pci_ioeventfd_handler, - NULL, NULL, &ioeventfd->virqfd, fd); + vfio_pci_ioeventfd_thread, NULL, + &ioeventfd->virqfd, fd); if (ret) { kfree(ioeventfd); goto out_unlock; -- 2.27.0