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docs/devel/qgraph: improve qgraph documentation 

Improve current qgraph documentation with a more concrete example
and clearer motivation.

This patch depends on the previous serie
"libqos/qgraph: format qgraph comments for sphinx documentation"

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Message-Id: <20210301092432.20342-1-eesposit@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
This commit is contained in:
Emanuele Giuseppe Esposito 2021-03-01 10:24:32 +01:00 committed by Thomas Huth
parent 222455ef81
commit afdbd38223
1 changed files with 412 additions and 105 deletions
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517
docs/devel/qgraph.rst
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@ -4,14 +4,37 @@
Qtest Driver Framework
========================================
This Qgraph API provides all basic functions to create a graph
and instantiate nodes representing machines, drivers and tests
representing their relations with ``CONSUMES``, ``PRODUCES``, and
``CONTAINS`` edges.
In order to test a specific driver, plain libqos tests need to
take care of booting QEMU with the right machine and devices.
This makes each test "hardcoded" for a specific configuration, reducing
the possible coverage that it can reach.
For example, the sdhci device is supported on both x86_64 and ARM boards,
therefore a generic sdhci test should test all machines and drivers that
support that device.
Using only libqos APIs, the test has to manually take care of
covering all the setups, and build the correct command line.
This also introduces backward compability issues: if a device/driver command
line name is changed, all tests that use that will not work
properly anymore and need to be adjusted.
The aim of qgraph is to create a graph of drivers, machines and tests such that
a test aimed to a certain driver does not have to care of
booting the right QEMU machine, pick the right device, build the command line
and so on. Instead, it only defines what type of device it is testing
(interface in qgraph terms) and the framework takes care of
covering all supported types of devices and machine architectures.
Following the above example, an interface would be ``sdhci``,
so the sdhci-test should only care of linking its qgraph node with
that interface. In this way, if the command line of a sdhci driver
is changed, only the respective qgraph driver node has to be adjusted.
The graph is composed by nodes that represent machines, drivers, tests
and edges that define the relationships between them (``CONSUMES``, ``PRODUCES``, and
``CONTAINS``).
The idea is to have a framework where each test asks for a specific
driver, and the framework takes care of allocating the proper devices
required and passing the correct command line arguments to QEMU.
Nodes
^^^^^^
@ -24,8 +47,11 @@ A node can be of four types:
drivers).
An interface is not explicitly created, it will be automatically
instantiated when a node consumes or produces it.
- **QNODE_TEST**: for example ``sdhci-test``, consumes an interface and
tests the functions provided.
An interface is simply a struct that abstracts the various drivers
for the same type of device, and offers an API to the nodes that
use it ("consume" relation in qgraph terms) that is implemented/backed up by the drivers that implement it ("produce" relation in qgraph terms).
- **QNODE_TEST**: for example ``sdhci-test``. A test consumes an interface
and tests the functions provided by it.
Notes for the nodes:
@ -69,136 +95,415 @@ available and only test that are reached by them will be executed.
Creating a new driver and its interface
"""""""""""""""""""""""""""""""""""""""""
.. code::
Here we continue the ``sdhci`` use case, with the following scenario:
- ``sdhci-test`` aims to test the ``read[q,w], writeq`` functions
offered by the ``sdhci`` drivers.
- The current ``sdhci`` device is supported by both ``x86_64/pc`` and ``ARM``
(in this example we focus on the ``arm-raspi2``) machines.
- QEMU offers 2 types of drivers: ``QSDHCI_MemoryMapped`` for ``ARM`` and
``QSDHCI_PCI`` for ``x86_64/pc``. Both implement the
``read[q,w], writeq`` functions.
In order to implement such scenario in qgraph, the test developer needs to:
- Create the ``x86_64/pc`` machine node. This machine uses the
``pci-bus`` architecture so it ``contains`` a PCI driver,
``pci-bus-pc``. The actual path is
``x86_64/pc --contains--> 1440FX-pcihost --contains-->
pci-bus-pc --produces--> pci-bus``.
For the sake of this example,
we do not focus on the PCI interface implementation.
- Create the ``sdhci-pci`` driver node, representing ``QSDHCI_PCI``.
The driver uses the PCI bus (and its API),
so it must ``consume`` the ``pci-bus`` generic interface (which abstracts
all the pci drivers available)
``sdhci-pci --consumes--> pci-bus``
- Create an ``arm/raspi2`` machine node. This machine ``contains``
a ``generic-sdhci`` memory mapped ``sdhci`` driver node, representing
``QSDHCI_MemoryMapped``.
``arm/raspi2 --contains--> generic-sdhci``
- Create the ``sdhci`` interface node. This interface offers the
functions that are shared by all ``sdhci`` devices.
The interface is produced by ``sdhci-pci`` and ``generic-sdhci``,
the available architecture-specific drivers.
``sdhci-pci --produces--> sdhci``
``generic-sdhci --produces--> sdhci``
- Create the ``sdhci-test`` test node. The test ``consumes`` the
``sdhci`` interface, using its API. It doesn't need to look at
the supported machines or drivers.
``sdhci-test --consumes--> sdhci``
``arm-raspi2`` machine, simplified from
``tests/qtest/libqos/arm-raspi2-machine.c``::
#include "qgraph.h"
struct My_driver {
struct QRaspi2Machine {
QOSGraphObject obj;
Node_produced prod;
Node_contained cont;
}
QGuestAllocator alloc;
QSDHCI_MemoryMapped sdhci;
};
static void my_destructor(QOSGraphObject *obj)
static void *raspi2_get_driver(void *object, const char *interface)
{
g_free(obj);
}
static void *my_get_driver(void *object, const char *interface) {
My_driver *dev = object;
if (!g_strcmp0(interface, "my_interface")) {
return &dev->prod;
QRaspi2Machine *machine = object;
if (!g_strcmp0(interface, "memory")) {
return &machine->alloc;
}
abort();
fprintf(stderr, "%s not present in arm/raspi2\n", interface);
g_assert_not_reached();
}
static void *my_get_device(void *object, const char *device) {
My_driver *dev = object;
if (!g_strcmp0(device, "my_driver_contained")) {
return &dev->cont;
static QOSGraphObject *raspi2_get_device(void *obj,
const char *device)
{
QRaspi2Machine *machine = obj;
if (!g_strcmp0(device, "generic-sdhci")) {
return &machine->sdhci.obj;
}
abort();
fprintf(stderr, "%s not present in arm/raspi2\n", device);
g_assert_not_reached();
}
static void *my_driver_constructor(void *node_consumed,
QOSGraphObject *alloc)
static void *qos_create_machine_arm_raspi2(QTestState *qts)
{
My_driver dev = g_new(My_driver, 1);
QRaspi2Machine *machine = g_new0(QRaspi2Machine, 1);
// get the node pointed by the produce edge
dev->obj.get_driver = my_get_driver;
alloc_init(&machine->alloc, ...);
// get the node pointed by the contains
dev->obj.get_device = my_get_device;
/* Get node(s) contained inside (CONTAINS) */
machine->obj.get_device = raspi2_get_device;
// free the object
dev->obj.destructor = my_destructor;
/* Get node(s) produced (PRODUCES) */
machine->obj.get_driver = raspi2_get_driver;
do_something_with_node_consumed(node_consumed);
// set all fields of contained device
init_contained_device(&dev->cont);
return &dev->obj;
/* free the object */
machine->obj.destructor = raspi2_destructor;
qos_init_sdhci_mm(&machine->sdhci, ...);
return &machine->obj;
}
static void register_my_driver(void)
static void raspi2_register_nodes(void)
{
qos_node_create_driver("my_driver", my_driver_constructor);
// contained drivers don't need a constructor,
// they will be init by the parent.
qos_node_create_driver("my_driver_contained", NULL);
// For the sake of this example, assume machine x86_64/pc
// contains "other_node".
// This relation, along with the machine and "other_node"
// creation, should be defined in the x86_64_pc-machine.c file.
// "my_driver" will then consume "other_node"
qos_node_contains("my_driver", "my_driver_contained");
qos_node_produces("my_driver", "my_interface");
qos_node_consumes("my_driver", "other_node");
/* arm/raspi2 --contains--> generic-sdhci */
qos_node_create_machine("arm/raspi2",
qos_create_machine_arm_raspi2);
qos_node_contains("arm/raspi2", "generic-sdhci", NULL);
}
In the above example, all possible types of relations are created:
node "my_driver" consumes, contains and produces other nodes.
More specifically::
libqos_init(raspi2_register_nodes);
x86_64/pc -->contains--> other_node <--consumes-- my_driver
|
my_driver_contained <--contains--+
|
my_interface <--produces--+
``x86_64/pc`` machine, simplified from
``tests/qtest/libqos/x86_64_pc-machine.c``::
#include "qgraph.h"
struct i440FX_pcihost {
QOSGraphObject obj;
QPCIBusPC pci;
};
struct QX86PCMachine {
QOSGraphObject obj;
QGuestAllocator alloc;
i440FX_pcihost bridge;
};
/* i440FX_pcihost */
static QOSGraphObject *i440FX_host_get_device(void *obj,
const char *device)
{
i440FX_pcihost *host = obj;
if (!g_strcmp0(device, "pci-bus-pc")) {
return &host->pci.obj;
}
fprintf(stderr, "%s not present in i440FX-pcihost\n", device);
g_assert_not_reached();
}
/* x86_64/pc machine */
static void *pc_get_driver(void *object, const char *interface)
{
QX86PCMachine *machine = object;
if (!g_strcmp0(interface, "memory")) {
return &machine->alloc;
}
fprintf(stderr, "%s not present in x86_64/pc\n", interface);
g_assert_not_reached();
}
static QOSGraphObject *pc_get_device(void *obj, const char *device)
{
QX86PCMachine *machine = obj;
if (!g_strcmp0(device, "i440FX-pcihost")) {
return &machine->bridge.obj;
}
fprintf(stderr, "%s not present in x86_64/pc\n", device);
g_assert_not_reached();
}
static void *qos_create_machine_pc(QTestState *qts)
{
QX86PCMachine *machine = g_new0(QX86PCMachine, 1);
/* Get node(s) contained inside (CONTAINS) */
machine->obj.get_device = pc_get_device;
/* Get node(s) produced (PRODUCES) */
machine->obj.get_driver = pc_get_driver;
/* free the object */
machine->obj.destructor = pc_destructor;
pc_alloc_init(&machine->alloc, qts, ALLOC_NO_FLAGS);
/* Get node(s) contained inside (CONTAINS) */
machine->bridge.obj.get_device = i440FX_host_get_device;
return &machine->obj;
}
static void pc_machine_register_nodes(void)
{
/* x86_64/pc --contains--> 1440FX-pcihost --contains-->
* pci-bus-pc [--produces--> pci-bus (in pci.h)] */
qos_node_create_machine("x86_64/pc", qos_create_machine_pc);
qos_node_contains("x86_64/pc", "i440FX-pcihost", NULL);
/* contained drivers don't need a constructor,
* they will be init by the parent */
qos_node_create_driver("i440FX-pcihost", NULL);
qos_node_contains("i440FX-pcihost", "pci-bus-pc", NULL);
}
libqos_init(pc_machine_register_nodes);
``sdhci`` taken from ``tests/qtest/libqos/sdhci.c``::
/* Interface node, offers the sdhci API */
struct QSDHCI {
uint16_t (*readw)(QSDHCI *s, uint32_t reg);
uint64_t (*readq)(QSDHCI *s, uint32_t reg);
void (*writeq)(QSDHCI *s, uint32_t reg, uint64_t val);
/* other fields */
};
/* Memory Mapped implementation of QSDHCI */
struct QSDHCI_MemoryMapped {
QOSGraphObject obj;
QSDHCI sdhci;
/* other driver-specific fields */
};
/* PCI implementation of QSDHCI */
struct QSDHCI_PCI {
QOSGraphObject obj;
QSDHCI sdhci;
/* other driver-specific fields */
};
/* Memory mapped implementation of QSDHCI */
static void *sdhci_mm_get_driver(void *obj, const char *interface)
{
QSDHCI_MemoryMapped *smm = obj;
if (!g_strcmp0(interface, "sdhci")) {
return &smm->sdhci;
}
fprintf(stderr, "%s not present in generic-sdhci\n", interface);
g_assert_not_reached();
}
void qos_init_sdhci_mm(QSDHCI_MemoryMapped *sdhci, QTestState *qts,
uint32_t addr, QSDHCIProperties *common)
{
/* Get node contained inside (CONTAINS) */
sdhci->obj.get_driver = sdhci_mm_get_driver;
/* SDHCI interface API */
sdhci->sdhci.readw = sdhci_mm_readw;
sdhci->sdhci.readq = sdhci_mm_readq;
sdhci->sdhci.writeq = sdhci_mm_writeq;
sdhci->qts = qts;
}
/* PCI implementation of QSDHCI */
static void *sdhci_pci_get_driver(void *object,
const char *interface)
{
QSDHCI_PCI *spci = object;
if (!g_strcmp0(interface, "sdhci")) {
return &spci->sdhci;
}
fprintf(stderr, "%s not present in sdhci-pci\n", interface);
g_assert_not_reached();
}
static void *sdhci_pci_create(void *pci_bus,
QGuestAllocator *alloc,
void *addr)
{
QSDHCI_PCI *spci = g_new0(QSDHCI_PCI, 1);
QPCIBus *bus = pci_bus;
uint64_t barsize;
qpci_device_init(&spci->dev, bus, addr);
/* SDHCI interface API */
spci->sdhci.readw = sdhci_pci_readw;
spci->sdhci.readq = sdhci_pci_readq;
spci->sdhci.writeq = sdhci_pci_writeq;
/* Get node(s) produced (PRODUCES) */
spci->obj.get_driver = sdhci_pci_get_driver;
spci->obj.start_hw = sdhci_pci_start_hw;
spci->obj.destructor = sdhci_destructor;
return &spci->obj;
}
static void qsdhci_register_nodes(void)
{
QOSGraphEdgeOptions opts = {
.extra_device_opts = "addr=04.0",
};
/* generic-sdhci */
/* generic-sdhci --produces--> sdhci */
qos_node_create_driver("generic-sdhci", NULL);
qos_node_produces("generic-sdhci", "sdhci");
/* sdhci-pci */
/* sdhci-pci --produces--> sdhci
* sdhci-pci --consumes--> pci-bus */
qos_node_create_driver("sdhci-pci", sdhci_pci_create);
qos_node_produces("sdhci-pci", "sdhci");
qos_node_consumes("sdhci-pci", "pci-bus", &opts);
}
libqos_init(qsdhci_register_nodes);
In the above example, all possible types of relations are created::
x86_64/pc --contains--> 1440FX-pcihost --contains--> pci-bus-pc
|
sdhci-pci --consumes--> pci-bus <--produces--+
|
+--produces--+
|
v
sdhci
^
|
+--produces-- +
|
arm/raspi2 --contains--> generic-sdhci
or inverting the consumes edge in consumed_by::
x86_64/pc -->contains--> other_node --consumed_by--> my_driver
x86_64/pc --contains--> 1440FX-pcihost --contains--> pci-bus-pc
|
my_driver_contained <--contains--+
|
my_interface <--produces--+
sdhci-pci <--consumed by-- pci-bus <--produces--+
|
+--produces--+
|
v
sdhci
^
|
+--produces-- +
|
arm/raspi2 --contains--> generic-sdhci
Creating new test
Adding a new test
"""""""""""""""""
.. code::
Given the above setup, adding a new test is very simple.
``sdhci-test``, taken from ``tests/qtest/sdhci-test.c``::
#include "qgraph.h"
static void my_test_function(void *obj, void *data)
static void check_capab_sdma(QSDHCI *s, bool supported)
{
Node_produced *interface_to_test = obj;
// test interface_to_test
uint64_t capab, capab_sdma;
capab = s->readq(s, SDHC_CAPAB);
capab_sdma = FIELD_EX64(capab, SDHC_CAPAB, SDMA);
g_assert_cmpuint(capab_sdma, ==, supported);
}
static void register_my_test(void)
static void test_registers(void *obj, void *data,
QGuestAllocator *alloc)
{
qos_add_test("my_interface", "my_test", my_test_function);
QSDHCI *s = obj;
/* example test */
check_capab_sdma(s, s->props.capab.sdma);
}
libqos_init(register_my_test);
static void register_sdhci_test(void)
{
/* sdhci-test --consumes--> sdhci */
qos_add_test("registers", "sdhci", test_registers, NULL);
}
Here a new test is created, consuming "my_interface" node
and creating a valid path from a machine to a test.
libqos_init(register_sdhci_test);
Here a new test is created, consuming ``sdhci`` interface node
and creating a valid path from both machines to a test.
Final graph will be like this::
x86_64/pc --contains--> other_node <--consumes-- my_driver
|
my_driver_contained <--contains--+
|
my_test --consumes--> my_interface <--produces--+
x86_64/pc --contains--> 1440FX-pcihost --contains--> pci-bus-pc
|
sdhci-pci --consumes--> pci-bus <--produces--+
|
+--produces--+
|
v
sdhci <--consumes-- sdhci-test
^
|
+--produces-- +
|
arm/raspi2 --contains--> generic-sdhci
or inverting the consumes edge in consumed_by::
x86_64/pc --contains--> other_node --consumed_by--> my_driver
x86_64/pc --contains--> 1440FX-pcihost --contains--> pci-bus-pc
|
my_driver_contained <--contains--+
|
my_test <--consumed_by-- my_interface <--produces--+
sdhci-pci <--consumed by-- pci-bus <--produces--+
|
+--produces--+
|
v
sdhci --consumed by--> sdhci-test
^
|
+--produces-- +
|
arm/raspi2 --contains--> generic-sdhci
Assuming there the binary is
``QTEST_QEMU_BINARY=./qemu-system-x86_64``
a valid test path will be:
``/x86_64/pc/other_node/my_driver/my_interface/my_test``.
``/x86_64/pc/1440FX-pcihost/pci-bus-pc/pci-bus/sdhci-pc/sdhci/sdhci-test``
and for the binary ``QTEST_QEMU_BINARY=./qemu-system-arm``:
``/arm/raspi2/generic-sdhci/sdhci/sdhci-test``
Additional examples are also in ``test-qgraph.c``
@ -215,19 +520,19 @@ There are three types of command line arguments:
``-device <device>``. It is automatically done by the framework.
- ``after node`` : added as additional argument to the node name.
This argument is added optionally when creating edges,
by setting the parameter @after_cmd_line and
@extra_edge_opts in #QOSGraphEdgeOptions.
by setting the parameter ``after_cmd_line`` and
``extra_edge_opts`` in ``QOSGraphEdgeOptions``.
The framework automatically adds
a comma before @extra_edge_opts,
a comma before ``extra_edge_opts``,
because it is going to add attributes
after the destination node pointed by
the edge containing these options, and automatically
adds a space before @after_cmd_line, because it
adds a space before ``after_cmd_line``, because it
adds an additional device, not an attribute.
- ``before node`` : added as additional argument to the node name.
This argument is added optionally when creating edges,
by setting the parameter @before_cmd_line in
#QOSGraphEdgeOptions. This attribute
by setting the parameter ``before_cmd_line`` in
``QOSGraphEdgeOptions``. This attribute
is going to add attributes before the destination node
pointed by the edge containing these options. It is
helpful to commands that are not node-representable,
@ -243,17 +548,19 @@ devices to be added in QEMU.
Example::
QOSGraphEdgeOptions opts = {
.arg = NULL,
.size_arg = 0,
.after_cmd_line = "-device other",
.before_cmd_line = "-netdev something",
.extra_edge_opts = "addr=04.0",
.before_cmd_line = "-drive id=drv0,if=none,file=null-co://,"
"file.read-zeroes=on,format=raw",
.after_cmd_line = "-device scsi-hd,bus=vs0.0,drive=drv0",
opts.extra_device_opts = "id=vs0";
};
QOSGraphNodeS *node = qos_node_create_driver("my_node", constructor);
qos_node_consumes_args("my_node", "interface", &opts);
qos_node_create_driver("virtio-scsi-device",
virtio_scsi_device_create);
qos_node_consumes("virtio-scsi-device", "virtio-bus", &opts);
Will produce the following command line:
``-netdev something -device my_node,addr=04.0 -device other``
``-drive id=drv0,if=none,file=null-co://, -device virtio-scsi-device,id=vs0 -device scsi-hd,bus=vs0.0,drive=drv0``
Qgraph API reference
^^^^^^^^^^^^^^^^^^^^