Re: [PATCH 22/31] vhost: Add VhostIOVATree

[Jason Wang <jasowang@redhat.com>]

在 2022/1/22 上午4:27, Eugenio Pérez 写道:
> This tree is able to look for a translated address from an IOVA address.
>
> At first glance it is similar to util/iova-tree. However, SVQ working on
> devices with limited IOVA space need more capabilities,


So did the IOVA tree (e.g l2 vtd can only work in the range of GAW and 
without RMRRs).


>   like allocating
> IOVA chunks or performing reverse translations (qemu addresses to iova).


This looks like a general request as well. So I wonder if we can simply 
extend iova tree instead.

Thanks


>
> The allocation capability, as "assign a free IOVA address to this chunk
> of memory in qemu's address space" allows shadow virtqueue to create a
> new address space that is not restricted by guest's addressable one, so
> we can allocate shadow vqs vrings outside of it.
>
> It duplicates the tree so it can search efficiently both directions,
> and it will signal overlap if iova or the translated address is
> present in any tree.
>
> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> ---
>   hw/virtio/vhost-iova-tree.h |  27 +++++++
>   hw/virtio/vhost-iova-tree.c | 157 ++++++++++++++++++++++++++++++++++++
>   hw/virtio/meson.build       |   2 +-
>   3 files changed, 185 insertions(+), 1 deletion(-)
>   create mode 100644 hw/virtio/vhost-iova-tree.h
>   create mode 100644 hw/virtio/vhost-iova-tree.c
>
> diff --git a/hw/virtio/vhost-iova-tree.h b/hw/virtio/vhost-iova-tree.h
> new file mode 100644
> index 0000000000..610394eaf1
> --- /dev/null
> +++ b/hw/virtio/vhost-iova-tree.h
> @@ -0,0 +1,27 @@
> +/*
> + * vhost software live migration ring
> + *
> + * SPDX-FileCopyrightText: Red Hat, Inc. 2021
> + * SPDX-FileContributor: Author: Eugenio Pérez <eperezma@redhat.com>
> + *
> + * SPDX-License-Identifier: GPL-2.0-or-later
> + */
> +
> +#ifndef HW_VIRTIO_VHOST_IOVA_TREE_H
> +#define HW_VIRTIO_VHOST_IOVA_TREE_H
> +
> +#include "qemu/iova-tree.h"
> +#include "exec/memory.h"
> +
> +typedef struct VhostIOVATree VhostIOVATree;
> +
> +VhostIOVATree *vhost_iova_tree_new(uint64_t iova_first, uint64_t iova_last);
> +void vhost_iova_tree_delete(VhostIOVATree *iova_tree);
> +G_DEFINE_AUTOPTR_CLEANUP_FUNC(VhostIOVATree, vhost_iova_tree_delete);
> +
> +const DMAMap *vhost_iova_tree_find_iova(const VhostIOVATree *iova_tree,
> +                                        const DMAMap *map);
> +int vhost_iova_tree_map_alloc(VhostIOVATree *iova_tree, DMAMap *map);
> +void vhost_iova_tree_remove(VhostIOVATree *iova_tree, const DMAMap *map);
> +
> +#endif
> diff --git a/hw/virtio/vhost-iova-tree.c b/hw/virtio/vhost-iova-tree.c
> new file mode 100644
> index 0000000000..0021dbaf54
> --- /dev/null
> +++ b/hw/virtio/vhost-iova-tree.c
> @@ -0,0 +1,157 @@
> +/*
> + * vhost software live migration ring
> + *
> + * SPDX-FileCopyrightText: Red Hat, Inc. 2021
> + * SPDX-FileContributor: Author: Eugenio Pérez <eperezma@redhat.com>
> + *
> + * SPDX-License-Identifier: GPL-2.0-or-later
> + */
> +
> +#include "qemu/osdep.h"
> +#include "qemu/iova-tree.h"
> +#include "vhost-iova-tree.h"
> +
> +#define iova_min_addr qemu_real_host_page_size
> +
> +/**
> + * VhostIOVATree, able to:
> + * - Translate iova address
> + * - Reverse translate iova address (from translated to iova)
> + * - Allocate IOVA regions for translated range (potentially slow operation)
> + *
> + * Note that it cannot remove nodes.
> + */
> +struct VhostIOVATree {
> +    /* First addresable iova address in the device */
> +    uint64_t iova_first;
> +
> +    /* Last addressable iova address in the device */
> +    uint64_t iova_last;
> +
> +    /* IOVA address to qemu memory maps. */
> +    IOVATree *iova_taddr_map;
> +
> +    /* QEMU virtual memory address to iova maps */
> +    GTree *taddr_iova_map;
> +};
> +
> +static gint vhost_iova_tree_cmp_taddr(gconstpointer a, gconstpointer b,
> +                                      gpointer data)
> +{
> +    const DMAMap *m1 = a, *m2 = b;
> +
> +    if (m1->translated_addr > m2->translated_addr + m2->size) {
> +        return 1;
> +    }
> +
> +    if (m1->translated_addr + m1->size < m2->translated_addr) {
> +        return -1;
> +    }
> +
> +    /* Overlapped */
> +    return 0;
> +}
> +
> +/**
> + * Create a new IOVA tree
> + *
> + * Returns the new IOVA tree
> + */
> +VhostIOVATree *vhost_iova_tree_new(hwaddr iova_first, hwaddr iova_last)
> +{
> +    VhostIOVATree *tree = g_new(VhostIOVATree, 1);
> +
> +    /* Some devices does not like 0 addresses */
> +    tree->iova_first = MAX(iova_first, iova_min_addr);
> +    tree->iova_last = iova_last;
> +
> +    tree->iova_taddr_map = iova_tree_new();
> +    tree->taddr_iova_map = g_tree_new_full(vhost_iova_tree_cmp_taddr, NULL,
> +                                           NULL, g_free);
> +    return tree;
> +}
> +
> +/**
> + * Delete an iova tree
> + */
> +void vhost_iova_tree_delete(VhostIOVATree *iova_tree)
> +{
> +    iova_tree_destroy(iova_tree->iova_taddr_map);
> +    g_tree_unref(iova_tree->taddr_iova_map);
> +    g_free(iova_tree);
> +}
> +
> +/**
> + * Find the IOVA address stored from a memory address
> + *
> + * @tree     The iova tree
> + * @map      The map with the memory address
> + *
> + * Return the stored mapping, or NULL if not found.
> + */
> +const DMAMap *vhost_iova_tree_find_iova(const VhostIOVATree *tree,
> +                                        const DMAMap *map)
> +{
> +    return g_tree_lookup(tree->taddr_iova_map, map);
> +}
> +
> +/**
> + * Allocate a new mapping
> + *
> + * @tree  The iova tree
> + * @map   The iova map
> + *
> + * Returns:
> + * - IOVA_OK if the map fits in the container
> + * - IOVA_ERR_INVALID if the map does not make sense (like size overflow)
> + * - IOVA_ERR_OVERLAP if the tree already contains that map
> + * - IOVA_ERR_NOMEM if tree cannot allocate more space.
> + *
> + * It returns assignated iova in map->iova if return value is VHOST_DMA_MAP_OK.
> + */
> +int vhost_iova_tree_map_alloc(VhostIOVATree *tree, DMAMap *map)
> +{
> +    /* Some vhost devices does not like addr 0. Skip first page */
> +    hwaddr iova_first = tree->iova_first ?: qemu_real_host_page_size;
> +    DMAMap *new;
> +    int r;
> +
> +    if (map->translated_addr + map->size < map->translated_addr ||
> +        map->perm == IOMMU_NONE) {
> +        return IOVA_ERR_INVALID;
> +    }
> +
> +    /* Check for collisions in translated addresses */
> +    if (vhost_iova_tree_find_iova(tree, map)) {
> +        return IOVA_ERR_OVERLAP;
> +    }
> +
> +    /* Allocate a node in IOVA address */
> +    r = iova_tree_alloc(tree->iova_taddr_map, map, iova_first,
> +                        tree->iova_last);
> +    if (r != IOVA_OK) {
> +        return r;
> +    }
> +
> +    /* Allocate node in qemu -> iova translations */
> +    new = g_malloc(sizeof(*new));
> +    memcpy(new, map, sizeof(*new));
> +    g_tree_insert(tree->taddr_iova_map, new, new);
> +    return IOVA_OK;
> +}
> +
> +/**
> + * Remove existing mappings from iova tree
> + *
> + * @param  iova_tree  The vhost iova tree
> + * @param  map        The map to remove
> + */
> +void vhost_iova_tree_remove(VhostIOVATree *iova_tree, const DMAMap *map)
> +{
> +    const DMAMap *overlap;
> +
> +    iova_tree_remove(iova_tree->iova_taddr_map, map);
> +    while ((overlap = vhost_iova_tree_find_iova(iova_tree, map))) {
> +        g_tree_remove(iova_tree->taddr_iova_map, overlap);
> +    }
> +}
> diff --git a/hw/virtio/meson.build b/hw/virtio/meson.build
> index 2dc87613bc..6047670804 100644
> --- a/hw/virtio/meson.build
> +++ b/hw/virtio/meson.build
> @@ -11,7 +11,7 @@ softmmu_ss.add(when: 'CONFIG_ALL', if_true: files('vhost-stub.c'))
>   
>   virtio_ss = ss.source_set()
>   virtio_ss.add(files('virtio.c'))
> -virtio_ss.add(when: 'CONFIG_VHOST', if_true: files('vhost.c', 'vhost-backend.c', 'vhost-shadow-virtqueue.c'))
> +virtio_ss.add(when: 'CONFIG_VHOST', if_true: files('vhost.c', 'vhost-backend.c', 'vhost-shadow-virtqueue.c', 'vhost-iova-tree.c'))
>   virtio_ss.add(when: 'CONFIG_VHOST_USER', if_true: files('vhost-user.c'))
>   virtio_ss.add(when: 'CONFIG_VHOST_VDPA', if_true: files('vhost-vdpa.c'))
>   virtio_ss.add(when: 'CONFIG_VIRTIO_BALLOON', if_true: files('virtio-balloon.c'))