On Sun, Jun 23, 2024 at 11:53:11PM -0700, Vivek Kasireddy wrote:
> From Jason Gunthorpe:
> "dma-buf has become a way to safely acquire a handle to non-struct page
> memory that can still have lifetime controlled by the exporter. Notably
> RDMA can now import dma-buf FDs and build them into MRs which allows for
> PCI P2P operations. Extend this to allow vfio-pci to export MMIO memory
> from PCI device BARs.
>
> The patch design loosely follows the pattern in commit
> db1a8dd916aa ("habanalabs: add support for dma-buf exporter") except this
> does not support pinning.
>
> Instead, this implements what, in the past, we've called a revocable
> attachment using move. In normal situations the attachment is pinned, as a
> BAR does not change physical address. However when the VFIO device is
> closed, or a PCI reset is issued, access to the MMIO memory is revoked.
>
> Revoked means that move occurs, but an attempt to immediately re-map the
> memory will fail. In the reset case a future move will be triggered when
> MMIO access returns. As both close and reset are under userspace control
> it is expected that userspace will suspend use of the dma-buf before doing
> these operations, the revoke is purely for kernel self-defense against a
> hostile userspace."
>
> Following enhancements are made to the original patch:
> - Add support for creating dmabuf from multiple areas (or ranges)
> - Add a mmap handler to provide CPU access to the dmabuf
>
> Original-patch-by: Jason Gunthorpe <j...@nvidia.com>
> Signed-off-by: Vivek Kasireddy <vivek.kasire...@intel.com>
I think this makes sense for dma-buf, so has my Ack. Bunch of things I've
spotted below, but overall looks all fine conceptually. Also a suggestion
for a dma-buf doc patch, so that we can collect acks from at least all
current dynamic importers whether they're code will be fine with this new
dma-buf.
For the actual use-case and upstream merging I think that's up to vfio and
rdma maintainers, at least to me doesn't feel it's impacting the gpu side.
Well maybe long-term people will also use this for gpus, there's
difinitely interest in direct upload to vram, but that's maybe more a
use-case where the nvme side will import gpu buffers.
Cheers, Sima
> ---
> drivers/vfio/pci/Makefile | 1 +
> drivers/vfio/pci/dma_buf.c | 438 +++++++++++++++++++++++++++++
> drivers/vfio/pci/vfio_pci_config.c | 22 +-
> drivers/vfio/pci/vfio_pci_core.c | 20 +-
> drivers/vfio/pci/vfio_pci_priv.h | 23 ++
> include/linux/vfio_pci_core.h | 1 +
> include/uapi/linux/vfio.h | 25 ++
> 7 files changed, 525 insertions(+), 5 deletions(-)
> create mode 100644 drivers/vfio/pci/dma_buf.c
>
> diff --git a/drivers/vfio/pci/Makefile b/drivers/vfio/pci/Makefile
> index cf00c0a7e55c..0cfdc9ede82f 100644
> --- a/drivers/vfio/pci/Makefile
> +++ b/drivers/vfio/pci/Makefile
> @@ -2,6 +2,7 @@
>
> vfio-pci-core-y := vfio_pci_core.o vfio_pci_intrs.o vfio_pci_rdwr.o
> vfio_pci_config.o
> vfio-pci-core-$(CONFIG_VFIO_PCI_ZDEV_KVM) += vfio_pci_zdev.o
> +vfio-pci-core-$(CONFIG_DMA_SHARED_BUFFER) += dma_buf.o
> obj-$(CONFIG_VFIO_PCI_CORE) += vfio-pci-core.o
>
> vfio-pci-y := vfio_pci.o
> diff --git a/drivers/vfio/pci/dma_buf.c b/drivers/vfio/pci/dma_buf.c
> new file mode 100644
> index 000000000000..68760677c6a0
> --- /dev/null
> +++ b/drivers/vfio/pci/dma_buf.c
> @@ -0,0 +1,438 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/* Copyright (c) 2024, NVIDIA CORPORATION & AFFILIATES.
> + */
> +#include <linux/dma-buf.h>
> +#include <linux/pci-p2pdma.h>
> +#include <linux/dma-resv.h>
> +
> +#include "vfio_pci_priv.h"
> +
> +MODULE_IMPORT_NS(DMA_BUF);
> +
> +struct vfio_pci_dma_buf {
> + struct dma_buf *dmabuf;
> + struct vfio_pci_core_device *vdev;
> + struct list_head dmabufs_elm;
> + unsigned int nr_ranges;
> + struct vfio_region_dma_range *dma_ranges;
> + unsigned int orig_nents;
> + bool revoked;
> +};
> +
> +static vm_fault_t vfio_pci_dma_buf_fault(struct vm_fault *vmf)
> +{
> + unsigned long addr = vmf->address - (vmf->pgoff << PAGE_SHIFT);
> + struct vm_area_struct *vma = vmf->vma;
> + struct vfio_pci_dma_buf *priv = vma->vm_private_data;
> + struct vfio_region_dma_range *dma_ranges = priv->dma_ranges;
> + unsigned long pfn, i, j;
> + phys_addr_t phys;
> + size_t offset;
> +
> + if (priv->revoked)
> + return VM_FAULT_SIGBUS;
->revoked seems to be protected by dma_resv_lock, except not here.
> +
> + down_read(&priv->vdev->memory_lock);
> +
> + for (i = 0, j = 0; i < priv->nr_ranges && j < vma_pages(vma); i++) {
> + phys = pci_resource_start(priv->vdev->pdev,
> + dma_ranges[i].region_index);
> + phys += dma_ranges[i].offset;
> +
> + for (offset = 0; offset != dma_ranges[i].length;) {
> + pfn = (phys + offset) >> PAGE_SHIFT;
> +
> + if (vmf_insert_pfn(vma, addr, pfn) != VM_FAULT_NOPAGE) {
> + up_read(&priv->vdev->memory_lock);
> + return VM_FAULT_SIGBUS;
> + }
> +
> + addr += PAGE_SIZE;
> + offset += PAGE_SIZE;
> + if (++j == vma_pages(vma))
> + break;
> + }
> + }
> +
> + up_read(&priv->vdev->memory_lock);
> +
> + return VM_FAULT_NOPAGE;
> +}
> +
> +static const struct vm_operations_struct vfio_pci_dma_buf_vmops = {
> + .fault = vfio_pci_dma_buf_fault,
> +};
> +
> +static int vfio_pci_dma_buf_mmap(struct dma_buf *dmabuf,
> + struct vm_area_struct *vma)
> +{
> + struct vfio_pci_dma_buf *priv = dmabuf->priv;
> + struct vfio_pci_core_device *vdev = priv->vdev;
> + struct vfio_region_dma_range *dma_ranges = priv->dma_ranges;
> + int i;
> +
> + if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) == 0)
> + return -EINVAL;
> +
> + for (i = 0; i < priv->nr_ranges; i++)
> + if (!vdev->bar_mmap_supported[dma_ranges[i].region_index])
> + return -EINVAL;
> +
> + vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
> + vma->vm_ops = &vfio_pci_dma_buf_vmops;
> + vma->vm_private_data = priv;
> + vm_flags_set(vma, VM_ALLOW_ANY_UNCACHED | VM_IO | VM_PFNMAP |
> + VM_DONTEXPAND | VM_DONTDUMP);
> + return 0;
> +}
> +
> +static int vfio_pci_dma_buf_attach(struct dma_buf *dmabuf,
> + struct dma_buf_attachment *attachment)
> +{
> + struct vfio_pci_dma_buf *priv = dmabuf->priv;
> + int rc;
> +
> + rc = pci_p2pdma_distance_many(priv->vdev->pdev, &attachment->dev, 1,
> + true);
> + if (rc < 0)
> + attachment->peer2peer = false;
> + return 0;
> +}
> +
> +static void vfio_pci_dma_buf_unpin(struct dma_buf_attachment *attachment)
> +{
> +}
> +
> +static int vfio_pci_dma_buf_pin(struct dma_buf_attachment *attachment)
> +{
> + /*
> + * Uses the dynamic interface but must always allow for
> + * dma_buf_move_notify() to do revoke
> + */
> + return -EINVAL;
> +}
> +
> +static int populate_sgt(struct dma_buf_attachment *attachment,
> + enum dma_data_direction dir,
> + struct sg_table *sgt, size_t sgl_size)
> +{
> + struct vfio_pci_dma_buf *priv = attachment->dmabuf->priv;
> + struct vfio_region_dma_range *dma_ranges = priv->dma_ranges;
> + size_t offset, chunk_size;
> + struct scatterlist *sgl;
> + dma_addr_t dma_addr;
> + phys_addr_t phys;
> + int i, j, ret;
> +
> + for_each_sgtable_sg(sgt, sgl, j)
> + sgl->length = 0;
> +
> + sgl = sgt->sgl;
> + for (i = 0; i < priv->nr_ranges; i++) {
> + phys = pci_resource_start(priv->vdev->pdev,
> + dma_ranges[i].region_index);
> + phys += dma_ranges[i].offset;
> +
> + /*
> + * Break the BAR's physical range up into max sized SGL's
> + * according to the device's requirement.
> + */
> + for (offset = 0; offset != dma_ranges[i].length;) {
> + chunk_size = min(dma_ranges[i].length - offset,
> + sgl_size);
> +
> + /*
> + * Since the memory being mapped is a device memory
> + * it could never be in CPU caches.
> + */
> + dma_addr = dma_map_resource(attachment->dev,
> + phys + offset,
> + chunk_size, dir,
> + DMA_ATTR_SKIP_CPU_SYNC);
> + ret = dma_mapping_error(attachment->dev, dma_addr);
> + if (ret)
> + goto err;
> +
> + sg_set_page(sgl, NULL, chunk_size, 0);
> + sg_dma_address(sgl) = dma_addr;
> + sg_dma_len(sgl) = chunk_size;
> + sgl = sg_next(sgl);
> + offset += chunk_size;
> + }
> + }
> +
> + return 0;
> +err:
> + for_each_sgtable_sg(sgt, sgl, j) {
> + if (!sg_dma_len(sgl))
> + continue;
> +
> + dma_unmap_resource(attachment->dev, sg_dma_address(sgl),
> + sg_dma_len(sgl),
> + dir, DMA_ATTR_SKIP_CPU_SYNC);
> + }
> +
> + return ret;
> +}
> +
> +static struct sg_table *
> +vfio_pci_dma_buf_map(struct dma_buf_attachment *attachment,
> + enum dma_data_direction dir)
> +{
> + size_t sgl_size = dma_get_max_seg_size(attachment->dev);
> + struct vfio_pci_dma_buf *priv = attachment->dmabuf->priv;
> + struct sg_table *sgt;
> + unsigned int nents;
> + int ret;
> +
> + dma_resv_assert_held(priv->dmabuf->resv);
> +
> + if (!attachment->peer2peer)
> + return ERR_PTR(-EPERM);
> +
> + if (priv->revoked)
> + return ERR_PTR(-ENODEV);
I think a doc patch to dma_buf_ops.map_dma_buf that ENODEV signals
terminal revocation would be good. That patch would also be a really good
place to collected Acks from all the stakeholders that they're fine with
this change, since thus far map_dma_buf pretty much only failed when we've
run out of (device) memory.
> +
> + sgt = kzalloc(sizeof(*sgt), GFP_KERNEL);
> + if (!sgt)
> + return ERR_PTR(-ENOMEM);
> +
> + nents = DIV_ROUND_UP(priv->dmabuf->size, sgl_size);
> + ret = sg_alloc_table(sgt, nents, GFP_KERNEL);
> + if (ret)
> + goto err_kfree_sgt;
> +
> + ret = populate_sgt(attachment, dir, sgt, sgl_size);
> + if (ret)
> + goto err_free_sgt;
> +
> + /*
> + * Because we are not going to include a CPU list we want to have some
> + * chance that other users will detect this by setting the orig_nents to
> + * 0 and using only nents (length of DMA list) when going over the sgl
> + */
> + priv->orig_nents = sgt->orig_nents;
> + sgt->orig_nents = 0;
> + return sgt;
> +
> +err_free_sgt:
> + sg_free_table(sgt);
> +err_kfree_sgt:
> + kfree(sgt);
> + return ERR_PTR(ret);
> +}
> +
> +static void vfio_pci_dma_buf_unmap(struct dma_buf_attachment *attachment,
> + struct sg_table *sgt,
> + enum dma_data_direction dir)
> +{
> + struct vfio_pci_dma_buf *priv = attachment->dmabuf->priv;
> + struct scatterlist *sgl;
> + int i;
> +
> + for_each_sgtable_dma_sg(sgt, sgl, i)
> + dma_unmap_resource(attachment->dev,
> + sg_dma_address(sgl),
> + sg_dma_len(sgl),
> + dir, DMA_ATTR_SKIP_CPU_SYNC);
> +
> + sgt->orig_nents = priv->orig_nents;
> + sg_free_table(sgt);
> + kfree(sgt);
> +}
> +
> +static void vfio_pci_dma_buf_release(struct dma_buf *dmabuf)
> +{
> + struct vfio_pci_dma_buf *priv = dmabuf->priv;
> +
> + /*
> + * Either this or vfio_pci_dma_buf_cleanup() will remove from the list.
> + * The refcount prevents both.
> + */
> + if (priv->vdev) {
> + down_write(&priv->vdev->memory_lock);
> + list_del_init(&priv->dmabufs_elm);
> + up_write(&priv->vdev->memory_lock);
> + vfio_device_put_registration(&priv->vdev->vdev);
> + }
> + kfree(priv);
> +}
> +
> +static const struct dma_buf_ops vfio_pci_dmabuf_ops = {
> + .attach = vfio_pci_dma_buf_attach,
> + .map_dma_buf = vfio_pci_dma_buf_map,
> + .pin = vfio_pci_dma_buf_pin,
> + .unpin = vfio_pci_dma_buf_unpin,
> + .release = vfio_pci_dma_buf_release,
> + .unmap_dma_buf = vfio_pci_dma_buf_unmap,
> + .mmap = vfio_pci_dma_buf_mmap,
> +};
> +
> +static int check_dma_ranges(struct vfio_pci_dma_buf *priv,
> + uint64_t *dmabuf_size)
> +{
> + struct vfio_region_dma_range *dma_ranges = priv->dma_ranges;
> + struct pci_dev *pdev = priv->vdev->pdev;
> + resource_size_t bar_size;
> + int i;
> +
> + for (i = 0; i < priv->nr_ranges; i++) {
> + /*
> + * For PCI the region_index is the BAR number like
> + * everything else.
> + */
> + if (dma_ranges[i].region_index >= VFIO_PCI_ROM_REGION_INDEX)
> + return -EINVAL;
> +
> + if (!IS_ALIGNED(dma_ranges[i].offset, PAGE_SIZE) ||
> + !IS_ALIGNED(dma_ranges[i].length, PAGE_SIZE))
> + return -EINVAL;
> +
> + bar_size = pci_resource_len(pdev, dma_ranges[i].region_index);
> + if (dma_ranges[i].offset > bar_size ||
> + dma_ranges[i].offset + dma_ranges[i].length > bar_size)
> + return -EINVAL;
> +
> + *dmabuf_size += dma_ranges[i].length;
> + }
> +
> + return 0;
> +}
> +
> +int vfio_pci_core_feature_dma_buf(struct vfio_pci_core_device *vdev, u32
> flags,
> + struct vfio_device_feature_dma_buf __user
> *arg,
> + size_t argsz)
> +{
> + struct vfio_device_feature_dma_buf get_dma_buf;
> + struct vfio_region_dma_range *dma_ranges;
> + DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
> + struct vfio_pci_dma_buf *priv;
> + uint64_t dmabuf_size = 0;
> + int ret;
> +
> + ret = vfio_check_feature(flags, argsz, VFIO_DEVICE_FEATURE_GET,
> + sizeof(get_dma_buf));
> + if (ret != 1)
> + return ret;
> +
> + if (copy_from_user(&get_dma_buf, arg, sizeof(get_dma_buf)))
> + return -EFAULT;
> +
> + dma_ranges = memdup_array_user(&arg->dma_ranges,
> + get_dma_buf.nr_ranges,
> + sizeof(*dma_ranges));
> + if (IS_ERR(dma_ranges))
> + return PTR_ERR(dma_ranges);
> +
> + priv = kzalloc(sizeof(*priv), GFP_KERNEL);
> + if (!priv) {
> + kfree(dma_ranges);
> + return -ENOMEM;
> + }
> +
> + priv->vdev = vdev;
> + priv->nr_ranges = get_dma_buf.nr_ranges;
> + priv->dma_ranges = dma_ranges;
> +
> + ret = check_dma_ranges(priv, &dmabuf_size);
> + if (ret)
> + goto err_free_priv;
> +
> + if (!vfio_device_try_get_registration(&vdev->vdev)) {
> + ret = -ENODEV;
> + goto err_free_priv;
> + }
> +
> + exp_info.ops = &vfio_pci_dmabuf_ops;
> + exp_info.size = dmabuf_size;
> + exp_info.flags = get_dma_buf.open_flags;
> + exp_info.priv = priv;
> +
> + priv->dmabuf = dma_buf_export(&exp_info);
> + if (IS_ERR(priv->dmabuf)) {
> + ret = PTR_ERR(priv->dmabuf);
> + goto err_dev_put;
> + }
> +
> + /* dma_buf_put() now frees priv */
> + INIT_LIST_HEAD(&priv->dmabufs_elm);
> + down_write(&vdev->memory_lock);
> + dma_resv_lock(priv->dmabuf->resv, NULL);
> + priv->revoked = !__vfio_pci_memory_enabled(vdev);
> + list_add_tail(&priv->dmabufs_elm, &vdev->dmabufs);
> + dma_resv_unlock(priv->dmabuf->resv);
> + up_write(&vdev->memory_lock);
> +
> + /*
> + * dma_buf_fd() consumes the reference, when the file closes the dmabuf
> + * will be released.
> + */
> + return dma_buf_fd(priv->dmabuf, get_dma_buf.open_flags);
> +
> +err_dev_put:
> + vfio_device_put_registration(&vdev->vdev);
> +err_free_priv:
> + kfree(dma_ranges);
> + kfree(priv);
> + return ret;
> +}
> +
> +static void revoke_mmap_mappings(struct vfio_pci_dma_buf *priv)
> +{
> + struct inode *inode = file_inode(priv->dmabuf->file);
> +
> + unmap_mapping_range(inode->i_mapping, 0, priv->dmabuf->size, true);
I was freaking out for a moment until I remembered we've long ago switched
over to per-dma_buf inodes :-)
> +}
> +
> +void vfio_pci_dma_buf_move(struct vfio_pci_core_device *vdev, bool revoked)
> +{
> + struct vfio_pci_dma_buf *priv;
> + struct vfio_pci_dma_buf *tmp;
> +
> + lockdep_assert_held_write(&vdev->memory_lock);
> +
> + list_for_each_entry_safe(priv, tmp, &vdev->dmabufs, dmabufs_elm) {
> + /*
> + * Returns true if a reference was successfully obtained.
> + * The caller must interlock with the dmabuf's release
> + * function in some way, such as RCU, to ensure that this
s/some way/by holding vdev->memory_lock/ because as-is this sounds a bit
too much like yolo locking ...
> + * is not called on freed memory.
> + */
> + if (!get_file_rcu(&priv->dmabuf->file))
> + continue;
> +
> + if (priv->revoked != revoked) {
> + dma_resv_lock(priv->dmabuf->resv, NULL);
> + priv->revoked = revoked;
> + dma_buf_move_notify(priv->dmabuf);
> +
> + if (revoked)
> + revoke_mmap_mappings(priv);
> +
> + dma_resv_unlock(priv->dmabuf->resv);
> + }
> + dma_buf_put(priv->dmabuf);
> + }
> +}
> +
> +void vfio_pci_dma_buf_cleanup(struct vfio_pci_core_device *vdev)
> +{
> + struct vfio_pci_dma_buf *priv;
> + struct vfio_pci_dma_buf *tmp;
> +
> + down_write(&vdev->memory_lock);
> + list_for_each_entry_safe(priv, tmp, &vdev->dmabufs, dmabufs_elm) {
> + if (!get_file_rcu(&priv->dmabuf->file))
> + continue;
> + dma_resv_lock(priv->dmabuf->resv, NULL);
> + list_del_init(&priv->dmabufs_elm);
> + priv->vdev = NULL;
> + priv->revoked = true;
> + dma_buf_move_notify(priv->dmabuf);
> + revoke_mmap_mappings(priv);
> + dma_resv_unlock(priv->dmabuf->resv);
> + vfio_device_put_registration(&vdev->vdev);
> + dma_buf_put(priv->dmabuf);
> + }
> + up_write(&vdev->memory_lock);
> +}
> diff --git a/drivers/vfio/pci/vfio_pci_config.c
> b/drivers/vfio/pci/vfio_pci_config.c
> index 97422aafaa7b..5cd7ec4b5e40 100644
> --- a/drivers/vfio/pci/vfio_pci_config.c
> +++ b/drivers/vfio/pci/vfio_pci_config.c
> @@ -585,10 +585,12 @@ static int vfio_basic_config_write(struct
> vfio_pci_core_device *vdev, int pos,
> virt_mem = !!(le16_to_cpu(*virt_cmd) & PCI_COMMAND_MEMORY);
> new_mem = !!(new_cmd & PCI_COMMAND_MEMORY);
>
> - if (!new_mem)
> + if (!new_mem) {
> vfio_pci_zap_and_down_write_memory_lock(vdev);
> - else
> + vfio_pci_dma_buf_move(vdev, true);
> + } else {
> down_write(&vdev->memory_lock);
> + }
>
> /*
> * If the user is writing mem/io enable (new_mem/io) and we
> @@ -623,6 +625,8 @@ static int vfio_basic_config_write(struct
> vfio_pci_core_device *vdev, int pos,
> *virt_cmd &= cpu_to_le16(~mask);
> *virt_cmd |= cpu_to_le16(new_cmd & mask);
>
> + if (__vfio_pci_memory_enabled(vdev))
> + vfio_pci_dma_buf_move(vdev, false);
> up_write(&vdev->memory_lock);
> }
>
> @@ -703,12 +707,16 @@ static int __init init_pci_cap_basic_perm(struct
> perm_bits *perm)
> static void vfio_lock_and_set_power_state(struct vfio_pci_core_device *vdev,
> pci_power_t state)
> {
> - if (state >= PCI_D3hot)
> + if (state >= PCI_D3hot) {
> vfio_pci_zap_and_down_write_memory_lock(vdev);
> - else
> + vfio_pci_dma_buf_move(vdev, true);
> + } else {
> down_write(&vdev->memory_lock);
> + }
>
> vfio_pci_set_power_state(vdev, state);
> + if (__vfio_pci_memory_enabled(vdev))
> + vfio_pci_dma_buf_move(vdev, false);
> up_write(&vdev->memory_lock);
> }
>
> @@ -896,7 +904,10 @@ static int vfio_exp_config_write(struct
> vfio_pci_core_device *vdev, int pos,
>
> if (!ret && (cap & PCI_EXP_DEVCAP_FLR)) {
> vfio_pci_zap_and_down_write_memory_lock(vdev);
> + vfio_pci_dma_buf_move(vdev, true);
> pci_try_reset_function(vdev->pdev);
> + if (__vfio_pci_memory_enabled(vdev))
> + vfio_pci_dma_buf_move(vdev, true);
> up_write(&vdev->memory_lock);
> }
> }
> @@ -978,7 +989,10 @@ static int vfio_af_config_write(struct
> vfio_pci_core_device *vdev, int pos,
>
> if (!ret && (cap & PCI_AF_CAP_FLR) && (cap & PCI_AF_CAP_TP)) {
> vfio_pci_zap_and_down_write_memory_lock(vdev);
> + vfio_pci_dma_buf_move(vdev, true);
> pci_try_reset_function(vdev->pdev);
> + if (__vfio_pci_memory_enabled(vdev))
> + vfio_pci_dma_buf_move(vdev, true);
> up_write(&vdev->memory_lock);
> }
> }
> diff --git a/drivers/vfio/pci/vfio_pci_core.c
> b/drivers/vfio/pci/vfio_pci_core.c
> index 3282ef2dddea..154129133d5e 100644
> --- a/drivers/vfio/pci/vfio_pci_core.c
> +++ b/drivers/vfio/pci/vfio_pci_core.c
> @@ -291,6 +291,8 @@ static int vfio_pci_runtime_pm_entry(struct
> vfio_pci_core_device *vdev,
> * semaphore.
> */
> vfio_pci_zap_and_down_write_memory_lock(vdev);
> + vfio_pci_dma_buf_move(vdev, true);
> +
> if (vdev->pm_runtime_engaged) {
> up_write(&vdev->memory_lock);
> return -EINVAL;
> @@ -374,6 +376,8 @@ static void vfio_pci_runtime_pm_exit(struct
> vfio_pci_core_device *vdev)
> */
> down_write(&vdev->memory_lock);
> __vfio_pci_runtime_pm_exit(vdev);
> + if (__vfio_pci_memory_enabled(vdev))
> + vfio_pci_dma_buf_move(vdev, false);
> up_write(&vdev->memory_lock);
> }
>
> @@ -694,6 +698,8 @@ void vfio_pci_core_close_device(struct vfio_device
> *core_vdev)
> #endif
> vfio_pci_core_disable(vdev);
>
> + vfio_pci_dma_buf_cleanup(vdev);
> +
> mutex_lock(&vdev->igate);
> if (vdev->err_trigger) {
> eventfd_ctx_put(vdev->err_trigger);
> @@ -1238,7 +1244,10 @@ static int vfio_pci_ioctl_reset(struct
> vfio_pci_core_device *vdev,
> */
> vfio_pci_set_power_state(vdev, PCI_D0);
>
> + vfio_pci_dma_buf_move(vdev, true);
> ret = pci_try_reset_function(vdev->pdev);
> + if (__vfio_pci_memory_enabled(vdev))
> + vfio_pci_dma_buf_move(vdev, false);
> up_write(&vdev->memory_lock);
>
> return ret;
> @@ -1527,6 +1536,8 @@ int vfio_pci_core_ioctl_feature(struct vfio_device
> *device, u32 flags,
> return vfio_pci_core_pm_exit(vdev, flags, arg, argsz);
> case VFIO_DEVICE_FEATURE_PCI_VF_TOKEN:
> return vfio_pci_core_feature_token(vdev, flags, arg, argsz);
> + case VFIO_DEVICE_FEATURE_DMA_BUF:
> + return vfio_pci_core_feature_dma_buf(vdev, flags, arg, argsz);
> default:
> return -ENOTTY;
> }
> @@ -2077,6 +2088,7 @@ int vfio_pci_core_init_dev(struct vfio_device
> *core_vdev)
> INIT_LIST_HEAD(&vdev->dummy_resources_list);
> INIT_LIST_HEAD(&vdev->ioeventfds_list);
> INIT_LIST_HEAD(&vdev->sriov_pfs_item);
> + INIT_LIST_HEAD(&vdev->dmabufs);
> init_rwsem(&vdev->memory_lock);
> xa_init(&vdev->ctx);
>
> @@ -2459,11 +2471,17 @@ static int vfio_pci_dev_set_hot_reset(struct
> vfio_device_set *dev_set,
> * cause the PCI config space reset without restoring the original
> * state (saved locally in 'vdev->pm_save').
> */
> - list_for_each_entry(vdev, &dev_set->device_list, vdev.dev_set_list)
> + list_for_each_entry(vdev, &dev_set->device_list, vdev.dev_set_list) {
> + vfio_pci_dma_buf_move(vdev, true);
> vfio_pci_set_power_state(vdev, PCI_D0);
> + }
>
> ret = pci_reset_bus(pdev);
>
> + list_for_each_entry(vdev, &dev_set->device_list, vdev.dev_set_list)
> + if (__vfio_pci_memory_enabled(vdev))
> + vfio_pci_dma_buf_move(vdev, false);
> +
> vdev = list_last_entry(&dev_set->device_list,
> struct vfio_pci_core_device, vdev.dev_set_list);
>
> diff --git a/drivers/vfio/pci/vfio_pci_priv.h
> b/drivers/vfio/pci/vfio_pci_priv.h
> index 5e4fa69aee16..09d3c300918c 100644
> --- a/drivers/vfio/pci/vfio_pci_priv.h
> +++ b/drivers/vfio/pci/vfio_pci_priv.h
> @@ -101,4 +101,27 @@ static inline bool vfio_pci_is_vga(struct pci_dev *pdev)
> return (pdev->class >> 8) == PCI_CLASS_DISPLAY_VGA;
> }
>
> +#ifdef CONFIG_DMA_SHARED_BUFFER
> +int vfio_pci_core_feature_dma_buf(struct vfio_pci_core_device *vdev, u32
> flags,
> + struct vfio_device_feature_dma_buf __user
> *arg,
> + size_t argsz);
> +void vfio_pci_dma_buf_cleanup(struct vfio_pci_core_device *vdev);
> +void vfio_pci_dma_buf_move(struct vfio_pci_core_device *vdev, bool revoked);
> +#else
> +static int
> +vfio_pci_core_feature_dma_buf(struct vfio_pci_core_device *vdev, u32 flags,
> + struct vfio_device_feature_dma_buf __user *arg,
> + size_t argsz)
> +{
> + return -ENOTTY;
> +}
> +static inline void vfio_pci_dma_buf_cleanup(struct vfio_pci_core_device
> *vdev)
> +{
> +}
> +static inline void vfio_pci_dma_buf_move(struct vfio_pci_core_device *vdev,
> + bool revoked)
> +{
> +}
> +#endif
> +
> #endif
> diff --git a/include/linux/vfio_pci_core.h b/include/linux/vfio_pci_core.h
> index f87067438ed4..3756e0904de2 100644
> --- a/include/linux/vfio_pci_core.h
> +++ b/include/linux/vfio_pci_core.h
> @@ -94,6 +94,7 @@ struct vfio_pci_core_device {
> struct vfio_pci_core_device *sriov_pf_core_dev;
> struct notifier_block nb;
> struct rw_semaphore memory_lock;
> + struct list_head dmabufs;
> };
>
> /* Will be exported for vfio pci drivers usage */
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 2b68e6cdf190..6f283dadacb7 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -1458,6 +1458,31 @@ struct vfio_device_feature_bus_master {
> };
> #define VFIO_DEVICE_FEATURE_BUS_MASTER 10
>
> +/**
> + * Upon VFIO_DEVICE_FEATURE_GET create a dma_buf fd for the
> + * regions selected.
> + *
> + * open_flags are the typical flags passed to open(2), eg O_RDWR, O_CLOEXEC,
> + * etc. offset/length specify a slice of the region to create the dmabuf
> from.
> + * nr_ranges is the total number of (P2P DMA) ranges that comprise the
> dmabuf.
> + *
> + * Return: The fd number on success, -1 and errno is set on failure.
> + */
> +#define VFIO_DEVICE_FEATURE_DMA_BUF 11
> +
> +struct vfio_region_dma_range {
> + __u32 region_index;
> + __u32 __pad;
> + __u64 offset;
> + __u64 length;
> +};
> +
> +struct vfio_device_feature_dma_buf {
> + __u32 open_flags;
> + __u32 nr_ranges;
> + struct vfio_region_dma_range dma_ranges[];
> +};
> +
> /* -------- API for Type1 VFIO IOMMU -------- */
>
> /**
> --
> 2.45.1
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
