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=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_2 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 0CA4BC33CB1 for ; Wed, 15 Jan 2020 14:07:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DCB8824656 for ; Wed, 15 Jan 2020 14:07:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729049AbgAOOHo (ORCPT ); Wed, 15 Jan 2020 09:07:44 -0500 Received: from foss.arm.com ([217.140.110.172]:37790 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726071AbgAOOHo (ORCPT ); Wed, 15 Jan 2020 09:07:44 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id C1D7B31B; Wed, 15 Jan 2020 06:07:43 -0800 (PST) Received: from donnerap.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id DB62F3F68E; Wed, 15 Jan 2020 06:07:42 -0800 (PST) Date: Wed, 15 Jan 2020 14:07:40 +0000 From: Andre Przywara To: Alexandru Elisei Cc: kvm@vger.kernel.org, will@kernel.org, julien.thierry.kdev@gmail.com, sami.mujawar@arm.com, lorenzo.pieralisi@arm.com Subject: Re: [PATCH kvmtool 04/16] Check that a PCI device's memory size is power of two Message-ID: <20200115140740.40881507@donnerap.cambridge.arm.com> In-Reply-To: <8800ef85-045e-f83d-6a43-d62f5cc8d8dd@arm.com> References: <20191125103033.22694-1-alexandru.elisei@arm.com> <20191125103033.22694-5-alexandru.elisei@arm.com> <20191127182514.23d719ff@donnerap.cambridge.arm.com> <8800ef85-045e-f83d-6a43-d62f5cc8d8dd@arm.com> Organization: ARM X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; aarch64-unknown-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Wed, 15 Jan 2020 12:43:20 +0000 Alexandru Elisei wrote: > Hi, > > On 11/27/19 6:25 PM, Andre Przywara wrote: > > On Mon, 25 Nov 2019 10:30:21 +0000 > > Alexandru Elisei wrote: > > > > Hi, > > > >> According to the PCI local bus specification [1], a device's memory size > >> must be a power of two. This is also implicit in the mechanism that a CPU > >> uses to get the memory size requirement for a PCI device. > >> > >> The vesa device requests a memory size that isn't a power of two. > >> According to the same spec [1], a device is allowed to consume more memory > >> than it actually requires. As a result, the amount of memory that the vesa > >> device now reserves has been increased. > >> > >> To prevent slip-ups in the future, a few BUILD_BUG_ON statements were added > >> in places where the memory size is known at compile time. > >> > >> [1] PCI Local Bus Specification Revision 3.0, section 6.2.5.1 > >> > >> Signed-off-by: Alexandru Elisei > >> --- > >> hw/vesa.c | 2 ++ > >> include/kvm/util.h | 2 ++ > >> include/kvm/vesa.h | 6 +++++- > >> vfio/pci.c | 5 +++++ > >> virtio/pci.c | 3 +++ > >> 5 files changed, 17 insertions(+), 1 deletion(-) > >> > >> diff --git a/hw/vesa.c b/hw/vesa.c > >> index f3c5114cf4fe..75670a51be5f 100644 > >> --- a/hw/vesa.c > >> +++ b/hw/vesa.c > >> @@ -58,6 +58,8 @@ struct framebuffer *vesa__init(struct kvm *kvm) > >> char *mem; > >> int r; > >> > >> + BUILD_BUG_ON(!is_power_of_two(VESA_MEM_SIZE)); > >> + > >> if (!kvm->cfg.vnc && !kvm->cfg.sdl && !kvm->cfg.gtk) > >> return NULL; > >> > >> diff --git a/include/kvm/util.h b/include/kvm/util.h > >> index 4ca7aa9392b6..e90f1c2db39f 100644 > >> --- a/include/kvm/util.h > >> +++ b/include/kvm/util.h > >> @@ -104,6 +104,8 @@ static inline unsigned long roundup_pow_of_two(unsigned long x) > >> return x ? 1UL << fls_long(x - 1) : 0; > >> } > >> > >> +#define is_power_of_two(x) ((x) ? ((x) & ((x) - 1)) == 0 : 0) > > This gives weird results for negative values (which the kernel avoids by having this a static inline and using an unsigned type). > > Not sure we care, but maybe (x > 0) ? ... would fix this? > > Good point, I will fix it by changing the implicit comparison against 0 at the > beginning with (x) > 0. > > > > >> + > >> struct kvm; > >> void *mmap_hugetlbfs(struct kvm *kvm, const char *htlbfs_path, u64 size); > >> void *mmap_anon_or_hugetlbfs(struct kvm *kvm, const char *hugetlbfs_path, u64 size); > >> diff --git a/include/kvm/vesa.h b/include/kvm/vesa.h > >> index 0fac11ab5a9f..e7d971343642 100644 > >> --- a/include/kvm/vesa.h > >> +++ b/include/kvm/vesa.h > >> @@ -5,8 +5,12 @@ > >> #define VESA_HEIGHT 480 > >> > >> #define VESA_MEM_ADDR 0xd0000000 > >> -#define VESA_MEM_SIZE (4*VESA_WIDTH*VESA_HEIGHT) > >> #define VESA_BPP 32 > >> +/* > >> + * We actually only need VESA_BPP/8*VESA_WIDTH*VESA_HEIGHT bytes. But the memory > >> + * size must be a power of 2, so we round up. > >> + */ > >> +#define VESA_MEM_SIZE (1 << 21) > > I don't think it's worth calculating the value and rounding it up, but can we have a BUILD_BUG checking that VESA_MEM_SIZE is big enough to hold the framebuffer? > > I'm not sure what you mean. The current value of VESA_MEM_SIZE is not a power of > two, which breaks the spec. That's the reason for changing it. Are you suggesting > that we keep VESA_MEM_SIZE = 1 << 21, we remove the power_of_two check and add a > BUILD_BUG on VESA_MEM_SIZE < 4 * VESA_WIDTH * VESA_HEIGHT? Only the latter, so keep the power_of_two check, but add the BUILD_BUG with the comparison. So that it breaks if someone increases the width or height. Cheers, Andre. > >> struct kvm; > >> struct biosregs; > >> diff --git a/vfio/pci.c b/vfio/pci.c > >> index 76e24c156906..914732cc6897 100644 > >> --- a/vfio/pci.c > >> +++ b/vfio/pci.c > >> @@ -831,6 +831,11 @@ static int vfio_pci_configure_bar(struct kvm *kvm, struct vfio_device *vdev, > >> /* Ignore invalid or unimplemented regions */ > >> if (!region->info.size) > >> return 0; > >> + if (!is_power_of_two(region->info.size)) { > >> + vfio_dev_err(vdev, "region is not power of two: 0x%llx", > >> + region->info.size); > >> + return -EINVAL; > >> + } > >> > >> if (pdev->irq_modes & VFIO_PCI_IRQ_MODE_MSIX) { > >> /* Trap and emulate MSI-X table */ > >> diff --git a/virtio/pci.c b/virtio/pci.c > >> index 99653cad2c0f..04e801827df9 100644 > >> --- a/virtio/pci.c > >> +++ b/virtio/pci.c > >> @@ -435,6 +435,9 @@ int virtio_pci__init(struct kvm *kvm, void *dev, struct virtio_device *vdev, > >> vpci->kvm = kvm; > >> vpci->dev = dev; > >> > >> + BUILD_BUG_ON(!is_power_of_two(IOPORT_SIZE)); > >> + BUILD_BUG_ON(!is_power_of_two(PCI_IO_SIZE)); > >> + > >> r = ioport__register(kvm, IOPORT_EMPTY, &virtio_pci__io_ops, IOPORT_SIZE, vdev); > >> if (r < 0) > >> return r;