Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933176AbaD1Tmq (ORCPT ); Mon, 28 Apr 2014 15:42:46 -0400 Received: from mx1.redhat.com ([209.132.183.28]:15859 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751690AbaD1Tmm (ORCPT ); Mon, 28 Apr 2014 15:42:42 -0400 Message-ID: <1398705857.24318.284.camel@ul30vt.home> Subject: Re: [RFC PATCH v5 07/11] VFIO_PLATFORM: Read and write support for the device fd From: Alex Williamson To: Antonios Motakis Cc: kvmarm@lists.cs.columbia.edu, iommu@lists.linux-foundation.org, tech@virtualopensystems.com, a.rigo@virtualopensystems.com, kvm@vger.kernel.org, christoffer.dall@linaro.org, will.deacon@arm.com, kim.phillips@freescale.com, stuart.yoder@freescale.com, open list Date: Mon, 28 Apr 2014 11:24:17 -0600 In-Reply-To: <1398700371-20096-8-git-send-email-a.motakis@virtualopensystems.com> References: <1398700371-20096-1-git-send-email-a.motakis@virtualopensystems.com> <1398700371-20096-8-git-send-email-a.motakis@virtualopensystems.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2014-04-28 at 17:52 +0200, Antonios Motakis wrote: > VFIO returns a file descriptor which we can use to manipulate the memory > regions of the device. Since some memory regions we cannot mmap due to > security concerns, we also allow to read and write to this file descriptor > directly. If there are regions we cannot mmap for security, why do we provide full read/write access to them? > Signed-off-by: Antonios Motakis > --- > drivers/vfio/platform/vfio_platform.c | 110 +++++++++++++++++++++++++++++++++- > 1 file changed, 107 insertions(+), 3 deletions(-) > > diff --git a/drivers/vfio/platform/vfio_platform.c b/drivers/vfio/platform/vfio_platform.c > index 5430cbe..7c01ced 100644 > --- a/drivers/vfio/platform/vfio_platform.c > +++ b/drivers/vfio/platform/vfio_platform.c > @@ -55,7 +55,8 @@ static int vfio_platform_regions_init(struct vfio_platform_device *vdev) > > region.addr = res->start; > region.size = resource_size(res); > - region.flags = 0; > + region.flags = VFIO_REGION_INFO_FLAG_READ > + | VFIO_REGION_INFO_FLAG_WRITE; > > vdev->region[i] = region; > } > @@ -153,13 +154,116 @@ static long vfio_platform_ioctl(void *device_data, > static ssize_t vfio_platform_read(void *device_data, char __user *buf, > size_t count, loff_t *ppos) > { > - return 0; > + struct vfio_platform_device *vdev = device_data; > + unsigned int index = VFIO_PLATFORM_OFFSET_TO_INDEX(*ppos); > + loff_t off = *ppos & VFIO_PLATFORM_OFFSET_MASK; > + unsigned int done = 0; > + void __iomem *io; > + > + if (index >= vdev->num_regions) > + return -EINVAL; > + > + io = ioremap_nocache(vdev->region[index].addr, > + vdev->region[index].size); I haven't looked at ioremap on arm, but if it's remotely non-trivially, it's probably a good idea to do this only on first access, cache it, and unmap it on region cleanup. Thanks, Alex > + > + while (count) { > + size_t filled; > + > + if (count >= 4 && !(off % 4)) { > + u32 val; > + > + val = ioread32(io + off); > + if (copy_to_user(buf, &val, 4)) > + goto err; > + > + filled = 4; > + } else if (count >= 2 && !(off % 2)) { > + u16 val; > + > + val = ioread16(io + off); > + if (copy_to_user(buf, &val, 2)) > + goto err; > + > + filled = 2; > + } else { > + u8 val; > + > + val = ioread8(io + off); > + if (copy_to_user(buf, &val, 1)) > + goto err; > + > + filled = 1; > + } > + > + > + count -= filled; > + done += filled; > + off += filled; > + buf += filled; > + } > + > + iounmap(io); > + return done; > +err: > + iounmap(io); > + return -EFAULT; > } > > static ssize_t vfio_platform_write(void *device_data, const char __user *buf, > size_t count, loff_t *ppos) > { > - return 0; > + struct vfio_platform_device *vdev = device_data; > + unsigned int index = VFIO_PLATFORM_OFFSET_TO_INDEX(*ppos); > + loff_t off = *ppos & VFIO_PLATFORM_OFFSET_MASK; > + unsigned int done = 0; > + void __iomem *io; > + > + if (index >= vdev->num_regions) > + return -EINVAL; > + > + io = ioremap_nocache(vdev->region[index].addr, > + vdev->region[index].size); > + > + while (count) { > + size_t filled; > + > + if (count >= 4 && !(off % 4)) { > + u32 val; > + > + if (copy_from_user(&val, buf, 4)) > + goto err; > + iowrite32(val, io + off); > + > + filled = 4; > + } else if (count >= 2 && !(off % 2)) { > + u16 val; > + > + if (copy_from_user(&val, buf, 2)) > + goto err; > + iowrite16(val, io + off); > + > + filled = 2; > + } else { > + u8 val; > + > + if (copy_from_user(&val, buf, 1)) > + goto err; > + iowrite8(val, io + off); > + > + filled = 1; > + } > + > + count -= filled; > + done += filled; > + off += filled; > + buf += filled; > + } > + > + iounmap(io); > + return done; > +err: > + iounmap(io); > + return -EFAULT; > } > > static int vfio_platform_mmap(void *device_data, struct vm_area_struct *vma) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/