Hi

On Tue, May 9, 2023 at 4:53 PM Albert Esteve <aest...@redhat.com> wrote:

>
>
> On Tue, May 9, 2023 at 12:53 PM Marc-André Lureau <
> marcandre.lur...@gmail.com> wrote:
>
>> Hi
>>
>> On Wed, May 3, 2023 at 12:21 PM Albert Esteve <aest...@redhat.com> wrote:
>>
>>> This API manages objects (in this iteration,
>>> dmabuf fds) that can be shared along different
>>> virtio devices.
>>>
>>> The API allows the different devices to add,
>>> remove and/or retrieve the objects by simply
>>> invoking the public functions that reside in the
>>> virtio-dmabuf file.
>>>
>>> Signed-off-by: Albert Esteve <aest...@redhat.com>
>>> ---
>>>  hw/display/meson.build            |   1 +
>>>  hw/display/virtio-dmabuf.c        |  88 +++++++++++++++++++++++
>>>  include/hw/virtio/virtio-dmabuf.h |  58 ++++++++++++++++
>>>  tests/unit/meson.build            |   1 +
>>>  tests/unit/test-virtio-dmabuf.c   | 112 ++++++++++++++++++++++++++++++
>>>  5 files changed, 260 insertions(+)
>>>  create mode 100644 hw/display/virtio-dmabuf.c
>>>  create mode 100644 include/hw/virtio/virtio-dmabuf.h
>>>  create mode 100644 tests/unit/test-virtio-dmabuf.c
>>>
>>> diff --git a/hw/display/meson.build b/hw/display/meson.build
>>> index 17165bd536..62a27395c0 100644
>>> --- a/hw/display/meson.build
>>> +++ b/hw/display/meson.build
>>> @@ -37,6 +37,7 @@ softmmu_ss.add(when: 'CONFIG_MACFB', if_true:
>>> files('macfb.c'))
>>>  softmmu_ss.add(when: 'CONFIG_NEXTCUBE', if_true: files('next-fb.c'))
>>>
>>>  softmmu_ss.add(when: 'CONFIG_VGA', if_true: files('vga.c'))
>>> +softmmu_ss.add(when: 'CONFIG_VIRTIO', if_true: files('virtio-dmabuf.c'))
>>>
>>>  if (config_all_devices.has_key('CONFIG_VGA_CIRRUS') or
>>>      config_all_devices.has_key('CONFIG_VGA_PCI') or
>>> diff --git a/hw/display/virtio-dmabuf.c b/hw/display/virtio-dmabuf.c
>>> new file mode 100644
>>> index 0000000000..3db939a2e3
>>> --- /dev/null
>>> +++ b/hw/display/virtio-dmabuf.c
>>> @@ -0,0 +1,88 @@
>>> +/*
>>> + * Virtio Shared dma-buf
>>> + *
>>> + * Copyright Red Hat, Inc. 2023
>>> + *
>>> + * Authors:
>>> + *     Albert Esteve <aest...@redhat.com>
>>> + *
>>> + * This work is licensed under the terms of the GNU GPL, version 2 or
>>> later.
>>> + * See the COPYING file in the top-level directory.
>>> + */
>>> +
>>> +#include "hw/virtio/virtio-dmabuf.h"
>>> +
>>> +
>>> +#define UUID_TO_POINTER(i) \
>>> +    ((gpointer)
>>> (g_intern_static_string(qemu_uuid_unparse_strdup((&i)))))
>>> +
>>>
>>
>> This will leak.
>>
>>
>
> Where did you spot the issue? The reference operator at `&i`? The cast to
> gpointer?
> I tried to mimic GINT_TO_POINTER macro here.
>

g_intern_static_string() takes a const char *, qemu_uuid_unparse_strdup()
returns an allocated string which you don't track or free (which you are
not supposed to with static_string). Anyway, you shouldn't need this API if
you implement hash and equal func for UUID as suggested.


>
>> +
>>> +static GMutex lock;
>>> +static GHashTable *resource_uuids;
>>> +
>>>
>>
>> Rather than having global variables, shouldn't we associate virtio
>> resources with the virtio bus instead?
>>
>>
>
> I am sorry but I am not sure how you mean. Wouldn't that mean to create a
> virtio-pci device with
> the virtio-dmabuf object? AFAIK the virtio-bus conforms the transport
> layer for connecting to the guest.
> The goal with virtio-dmabuf is "connecting" different virtio
> backends, which are already connected to the
> virtio-bus (and the guest). Strictly speaking not even that, just needs to
> be accessible from different devices
> to add and retrieve descriptors (dealing with concurrent accesses).
>
> But maybe I am not understanding your point!
>

All the virtio devices are attached to a virtio bus. Thus I think shared
resource tracking should be implemented on the bus. Maybe Michael could
comment on that first.


>
>
>
>> +
>>> +static bool virtio_add_resource(QemuUUID uuid, gpointer value)
>>> +{
>>> +    gpointer struuid = UUID_TO_POINTER(uuid);
>>> +    if (resource_uuids == NULL) {
>>> +        resource_uuids = g_hash_table_new_full(NULL, NULL, NULL,
>>> g_free);
>>>
>>
>> You create "resource_uuids" implicitly in 2 places, in 2 different ways.
>> Let's not do that, and have an explicit initialization step instead (it
>> might be with the virtio bus construction, if we move the code there)
>>
>>
> Ok!
>
>
>> +    } else if (g_hash_table_lookup(resource_uuids, struuid) != NULL) {
>>>
>>
>> You could implement a hash_func and key_equal_func for QemuUUID instead.
>>
>>
>
> Sounds like a good idea. I will add an initial, separate commit for that.
>
>
>> +        return false;
>>> +    }
>>> +
>>> +    return g_hash_table_insert(resource_uuids, struuid, value);
>>> +}
>>> +
>>> +static gpointer virtio_lookup_resource(QemuUUID uuid)
>>> +{
>>> +    if (resource_uuids == NULL) {
>>> +        return NULL;
>>> +    }
>>> +
>>> +    return g_hash_table_lookup(resource_uuids, UUID_TO_POINTER(uuid));
>>> +}
>>> +
>>> +bool virtio_add_dmabuf(QemuUUID uuid, int udmabuf_fd)
>>> +{
>>> +    bool result;
>>> +    if (udmabuf_fd < 0) {
>>> +        return false;
>>> +    }
>>> +    g_mutex_lock(&lock);
>>> +    if (resource_uuids == NULL) {
>>> +        resource_uuids = g_hash_table_new(NULL, NULL);
>>> +    }
>>> +    result = virtio_add_resource(uuid, GINT_TO_POINTER(udmabuf_fd));
>>> +    g_mutex_unlock(&lock);
>>> +
>>> +    return result;
>>> +}
>>> +
>>> +bool virtio_remove_resource(QemuUUID uuid)
>>> +{
>>> +    bool result;
>>> +    g_mutex_lock(&lock);
>>> +    result = g_hash_table_remove(resource_uuids, UUID_TO_POINTER(uuid));
>>> +    g_mutex_unlock(&lock);
>>> +
>>> +    return result;
>>> +}
>>> +
>>> +int virtio_lookup_dmabuf(QemuUUID uuid)
>>> +{
>>> +    g_mutex_lock(&lock);
>>> +    gpointer lookup_res = virtio_lookup_resource(uuid);
>>> +    g_mutex_unlock(&lock);
>>> +    if (lookup_res == NULL) {
>>> +        return -1;
>>> +    }
>>> +
>>> +    return GPOINTER_TO_INT(lookup_res);
>>> +}
>>> +
>>> +void virtio_free_resources(void)
>>> +{
>>> +    g_hash_table_destroy(resource_uuids);
>>> +    /* Reference count shall be 0 after the implicit unref on destroy */
>>> +    resource_uuids = NULL;
>>> +}
>>> diff --git a/include/hw/virtio/virtio-dmabuf.h
>>> b/include/hw/virtio/virtio-dmabuf.h
>>> new file mode 100644
>>> index 0000000000..1c1c713128
>>> --- /dev/null
>>> +++ b/include/hw/virtio/virtio-dmabuf.h
>>> @@ -0,0 +1,58 @@
>>> +/*
>>> + * Virtio Shared dma-buf
>>> + *
>>> + * Copyright Red Hat, Inc. 2023
>>> + *
>>> + * Authors:
>>> + *     Albert Esteve <aest...@redhat.com>
>>> + *
>>> + * This work is licensed under the terms of the GNU GPL, version 2.
>>> + * See the COPYING file in the top-level directory.
>>> + */
>>> +
>>> +#ifndef VIRTIO_DMABUF_H
>>> +#define VIRTIO_DMABUF_H
>>> +
>>> +#include "qemu/osdep.h"
>>> +
>>> +#include <glib.h>
>>> +#include "qemu/uuid.h"
>>> +
>>> +/**
>>> + * virtio_add_dmabuf() - Add a new dma-buf resource to the lookup table
>>> + * @uuid: new resource's UUID
>>> + * @dmabuf_fd: the dma-buf descriptor that will be stored and shared
>>> with
>>> + *             other virtio devices
>>>
>>
>> The comment should be clear about fd ownership. In this case, it looks
>> like it's the caller's responsibility to properly handle its lifecycle.
>>
>>
>
> Sure.
>
>
>> + *
>>> + * Note: @dmabuf_fd must be a valid (non-negative) file descriptor.
>>> + *
>>> + * Return: true if the UUID did not exist and the resource has been
>>> added,
>>> + * false if another resource with the same UUID already existed.
>>> + * Note that if it finds a repeated UUID, the resource is not inserted
>>> in
>>> + * the lookup table.
>>> + */
>>> +bool virtio_add_dmabuf(QemuUUID uuid, int dmabuf_fd);
>>> +
>>> +/**
>>> + * virtio_remove_resource() - Removes a resource from the lookup table
>>> + * @uuid: resource's UUID
>>> + *
>>> + * Return: true if the UUID has been found and removed from the lookup
>>> table.
>>> + */
>>> +bool virtio_remove_resource(QemuUUID uuid);
>>> +
>>> +/**
>>> + * virtio_lookup_dmabuf() - Looks for a dma-buf resource in the lookup
>>> table
>>> + * @uuid: resource's UUID
>>> + *
>>> + * Return: the dma-buf file descriptor integer, or -1 if the key is not
>>> found.
>>> + */
>>> +int virtio_lookup_dmabuf(QemuUUID uuid);
>>> +
>>> +/**
>>> + * virtio_free_resources() - Destroys all keys and values of the shared
>>> + * resources lookup table, and frees them
>>> + */
>>> +void virtio_free_resources(void);
>>>
>>
>> If it's part of the virtio bus, we won't need to have an API for it, it
>> will be done as part of object destruction.
>>
>
>>
>>> +
>>> +#endif /* VIRTIO_DMABUF_H */
>>> diff --git a/tests/unit/meson.build b/tests/unit/meson.build
>>> index 3bc78d8660..eb2a1a8872 100644
>>> --- a/tests/unit/meson.build
>>> +++ b/tests/unit/meson.build
>>> @@ -50,6 +50,7 @@ tests = {
>>>    'test-qapi-util': [],
>>>    'test-interval-tree': [],
>>>    'test-xs-node': [qom],
>>> +  'test-virtio-dmabuf': [meson.project_source_root() /
>>> 'hw/display/virtio-dmabuf.c'],
>>>  }
>>>
>>>  if have_system or have_tools
>>> diff --git a/tests/unit/test-virtio-dmabuf.c
>>> b/tests/unit/test-virtio-dmabuf.c
>>> new file mode 100644
>>> index 0000000000..063830c91c
>>> --- /dev/null
>>> +++ b/tests/unit/test-virtio-dmabuf.c
>>> @@ -0,0 +1,112 @@
>>> +/*
>>> + * QEMU tests for shared dma-buf API
>>> + *
>>> + * Copyright (c) 2023 Red Hat, Inc.
>>> + *
>>> + * This library is free software; you can redistribute it and/or
>>> + * modify it under the terms of the GNU Lesser General Public
>>> + * License as published by the Free Software Foundation; either
>>> + * version 2.1 of the License, or (at your option) any later version.
>>> + *
>>> + * This library is distributed in the hope that it will be useful,
>>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>>> + * Lesser General Public License for more details.
>>> + *
>>> + * You should have received a copy of the GNU Lesser General Public
>>> + * License along with this library; if not, see <
>>> http://www.gnu.org/licenses/>.
>>> + *
>>> + */
>>> +
>>> +#include "qemu/osdep.h"
>>> +#include "hw/virtio/virtio-dmabuf.h"
>>> +
>>> +
>>> +static void test_add_remove_resources(void)
>>> +{
>>> +    QemuUUID uuid;
>>> +    int i, dmabuf_fd;
>>> +
>>> +    for (i = 0; i < 100; ++i) {
>>> +        qemu_uuid_generate(&uuid);
>>> +        dmabuf_fd = g_random_int_range(3, 500);
>>> +        /* Add a new resource */
>>> +        g_assert(virtio_add_dmabuf(uuid, dmabuf_fd));
>>> +        g_assert_cmpint(virtio_lookup_dmabuf(uuid), ==, dmabuf_fd);
>>> +        /* Remove the resource */
>>> +        g_assert(virtio_remove_resource(uuid));
>>> +        /* Resource is not found anymore */
>>> +        g_assert_cmpint(virtio_lookup_dmabuf(uuid), ==, -1);
>>> +    }
>>> +}
>>> +
>>> +static void test_remove_invalid_resource(void)
>>> +{
>>> +    QemuUUID uuid;
>>> +    int i;
>>> +
>>> +    for (i = 0; i < 20; ++i) {
>>> +        qemu_uuid_generate(&uuid);
>>> +        g_assert_cmpint(virtio_lookup_dmabuf(uuid), ==, -1);
>>> +        /* Removing a resource that does not exist returns false */
>>> +        g_assert_false(virtio_remove_resource(uuid));
>>> +    }
>>> +}
>>> +
>>> +static void test_add_invalid_resource(void)
>>> +{
>>> +    QemuUUID uuid;
>>> +    int i, dmabuf_fd = -2, alt_dmabuf = 2;
>>> +
>>> +    for (i = 0; i < 20; ++i) {
>>> +        qemu_uuid_generate(&uuid);
>>> +        /* Add a new resource with invalid (negative) resource fd */
>>> +        g_assert_false(virtio_add_dmabuf(uuid, dmabuf_fd));
>>> +        /* Resource is not found */
>>> +        g_assert_cmpint(virtio_lookup_dmabuf(uuid), ==, -1);
>>> +    }
>>> +
>>> +    for (i = 0; i < 20; ++i) {
>>> +        /* Add a valid resource */
>>> +        qemu_uuid_generate(&uuid);
>>> +        dmabuf_fd = g_random_int_range(3, 500);
>>> +        g_assert(virtio_add_dmabuf(uuid, dmabuf_fd));
>>> +        g_assert_cmpint(virtio_lookup_dmabuf(uuid), ==, dmabuf_fd);
>>> +        /* Add a new resource with repeated uuid returns false */
>>> +        g_assert_false(virtio_add_dmabuf(uuid, alt_dmabuf));
>>> +        /* The value for the uuid key is not replaced */
>>> +        g_assert_cmpint(virtio_lookup_dmabuf(uuid), ==, dmabuf_fd);
>>> +    }
>>> +}
>>> +
>>> +static void test_free_resources(void)
>>> +{
>>> +    QemuUUID uuids[20];
>>> +    int i, dmabuf_fd;
>>> +
>>> +    for (i = 0; i < ARRAY_SIZE(uuids); ++i) {
>>> +        qemu_uuid_generate(&uuids[i]);
>>> +        dmabuf_fd = g_random_int_range(3, 500);
>>> +        g_assert(virtio_add_dmabuf(uuids[i], dmabuf_fd));
>>> +        g_assert_cmpint(virtio_lookup_dmabuf(uuids[i]), ==, dmabuf_fd);
>>> +    }
>>> +    virtio_free_resources();
>>> +    for (i = 0; i < ARRAY_SIZE(uuids); ++i) {
>>> +        /* None of the resources is found after free'd */
>>> +        g_assert_cmpint(virtio_lookup_dmabuf(uuids[i]), ==, -1);
>>> +    }
>>> +
>>> +}
>>> +
>>> +int main(int argc, char **argv)
>>> +{
>>> +    g_test_init(&argc, &argv, NULL);
>>> +    g_test_add_func("/virtio-dmabuf/add_rm_res",
>>> test_add_remove_resources);
>>> +    g_test_add_func("/virtio-dmabuf/rm_invalid_res",
>>> +                    test_remove_invalid_resource);
>>> +    g_test_add_func("/virtio-dmabuf/add_invalid_res",
>>> +                    test_add_invalid_resource);
>>> +    g_test_add_func("/virtio-dmabuf/free_res", test_free_resources);
>>> +
>>> +    return g_test_run();
>>> +}
>>> --
>>> 2.40.0
>>>
>>>
>>>
>>
>> --
>> Marc-André Lureau
>>
>

-- 
Marc-André Lureau

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