libvirt/tests/qemuxml2xmltest.c
Laine Stump e9bd5c0e24 Add txmode attribute to interface XML for virtio backend
This is in response to:

   https://bugzilla.redhat.com/show_bug.cgi?id=629662

Explanation

qemu's virtio-net-pci driver allows setting the algorithm used for tx
packets to either "bh" or "timer". This is done by adding ",tx=bh" or
",tx=timer" to the "-device virtio-net-pci" commandline option.

'bh' stands for 'bottom half'; when this is set, packet tx is all done
in an iothread in the bottom half of the driver. (In libvirt, this
option is called the more descriptive "iothread".)

'timer' means that tx work is done in qemu, and if there is more tx
data than can be sent at the present time, a timer is set before qemu
moves on to do other things; when the timer fires, another attempt is
made to send more data. (libvirt retains the name "timer" for this
option.)

The resulting difference, according to the qemu developer who added
the option is:

    bh makes tx more asynchronous and reduces latency, but potentially
    causes more processor bandwidth contention since the cpu doing the
    tx isn't necessarily the cpu where the guest generated the
    packets.

Solution

This patch provides a libvirt domain xml knob to change the option on
the qemu commandline, by adding a new attribute "txmode" to the
<driver> element that can be placed inside any <interface> element in
a domain definition. It's use would be something like this:

    <interface ...>
      ...
      <model type='virtio'/>
      <driver txmode='iothread'/>
      ...
    </interface>

I chose to put this setting as an attribute to <driver> rather than as
a sub-element to <tune> because it is specific to the virtio-net
driver, not something that is generally usable by all network drivers.
(note that this is the same placement as the "driver name=..."
attribute used to choose kernel vs. userland backend for the
virtio-net driver.)

Actually adding the tx=xxx option to the qemu commandline is only done
if the version of qemu being used advertises it in the output of

    qemu -device virtio-net-pci,?

If a particular txmode is requested in the XML, and the option isn't
listed in that help output, an UNSUPPORTED_CONFIG error is logged, and
the domain fails to start.
2011-02-17 11:07:58 -05:00

209 lines
5.2 KiB
C

#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <fcntl.h>
#ifdef WITH_QEMU
# include "internal.h"
# include "testutils.h"
# include "qemu/qemu_conf.h"
# include "testutilsqemu.h"
static char *progname;
static char *abs_srcdir;
static struct qemud_driver driver;
# define MAX_FILE 4096
static int testCompareXMLToXMLFiles(const char *inxml, const char *outxml) {
char inXmlData[MAX_FILE];
char *inXmlPtr = &(inXmlData[0]);
char outXmlData[MAX_FILE];
char *outXmlPtr = &(outXmlData[0]);
char *actual = NULL;
int ret = -1;
virDomainDefPtr def = NULL;
if (virtTestLoadFile(inxml, &inXmlPtr, MAX_FILE) < 0)
goto fail;
if (virtTestLoadFile(outxml, &outXmlPtr, MAX_FILE) < 0)
goto fail;
if (!(def = virDomainDefParseString(driver.caps, inXmlData,
VIR_DOMAIN_XML_INACTIVE)))
goto fail;
if (!(actual = virDomainDefFormat(def, 0)))
goto fail;
if (STRNEQ(outXmlData, actual)) {
virtTestDifference(stderr, outXmlData, actual);
goto fail;
}
ret = 0;
fail:
free(actual);
virDomainDefFree(def);
return ret;
}
struct testInfo {
const char *name;
int different;
};
static int testCompareXMLToXMLHelper(const void *data) {
const struct testInfo *info = data;
char xml_in[PATH_MAX];
char xml_out[PATH_MAX];
int ret;
snprintf(xml_in, PATH_MAX, "%s/qemuxml2argvdata/qemuxml2argv-%s.xml",
abs_srcdir, info->name);
snprintf(xml_out, PATH_MAX, "%s/qemuxml2xmloutdata/qemuxml2xmlout-%s.xml",
abs_srcdir, info->name);
if (info->different) {
ret = testCompareXMLToXMLFiles(xml_in, xml_out);
} else {
ret = testCompareXMLToXMLFiles(xml_in, xml_in);
}
return ret;
}
static int
mymain(int argc, char **argv)
{
int ret = 0;
char cwd[PATH_MAX];
progname = argv[0];
if (argc > 1) {
fprintf(stderr, "Usage: %s\n", progname);
return (EXIT_FAILURE);
}
abs_srcdir = getenv("abs_srcdir");
if (!abs_srcdir)
abs_srcdir = getcwd(cwd, sizeof(cwd));
if ((driver.caps = testQemuCapsInit()) == NULL)
return (EXIT_FAILURE);
# define DO_TEST_FULL(name, is_different) \
do { \
const struct testInfo info = {name, is_different}; \
if (virtTestRun("QEMU XML-2-XML " name, \
1, testCompareXMLToXMLHelper, &info) < 0) \
ret = -1; \
} while (0)
# define DO_TEST(name) \
DO_TEST_FULL(name, 0)
# define DO_TEST_DIFFERENT(name) \
DO_TEST_FULL(name, 1)
/* Unset or set all envvars here that are copied in qemudBuildCommandLine
* using ADD_ENV_COPY, otherwise these tests may fail due to unexpected
* values for these envvars */
setenv("PATH", "/bin", 1);
DO_TEST("minimal");
DO_TEST("boot-cdrom");
DO_TEST("boot-network");
DO_TEST("boot-floppy");
DO_TEST("boot-multi");
DO_TEST("boot-menu-disable");
DO_TEST("boot-order");
DO_TEST("bootloader");
DO_TEST("clock-utc");
DO_TEST("clock-localtime");
DO_TEST("hugepages");
DO_TEST("disk-aio");
DO_TEST("disk-cdrom");
DO_TEST("disk-floppy");
DO_TEST("disk-many");
DO_TEST("disk-xenvbd");
DO_TEST("disk-usb");
DO_TEST("disk-virtio");
DO_TEST("floppy-drive-fat");
DO_TEST("disk-drive-fat");
DO_TEST("disk-drive-fmt-qcow");
DO_TEST("disk-drive-cache-v1-wt");
DO_TEST("disk-drive-cache-v1-wb");
DO_TEST("disk-drive-cache-v1-none");
DO_TEST("disk-scsi-device");
DO_TEST("graphics-vnc");
DO_TEST("graphics-vnc-sasl");
DO_TEST("graphics-vnc-tls");
DO_TEST("graphics-sdl");
DO_TEST("graphics-sdl-fullscreen");
DO_TEST("graphics-spice");
DO_TEST("input-usbmouse");
DO_TEST("input-usbtablet");
DO_TEST("input-xen");
DO_TEST("misc-acpi");
DO_TEST("misc-no-reboot");
DO_TEST("net-user");
DO_TEST("net-virtio");
DO_TEST("net-virtio-device");
DO_TEST("net-eth");
DO_TEST("net-eth-ifname");
DO_TEST("sound");
DO_TEST("serial-vc");
DO_TEST("serial-pty");
DO_TEST("serial-dev");
DO_TEST("serial-file");
DO_TEST("serial-unix");
DO_TEST("serial-tcp");
DO_TEST("serial-udp");
DO_TEST("serial-tcp-telnet");
DO_TEST("serial-many");
DO_TEST("parallel-tcp");
DO_TEST("console-compat");
DO_TEST("channel-guestfwd");
DO_TEST("channel-virtio");
DO_TEST("hostdev-usb-address");
DO_TEST("hostdev-pci-address");
DO_TEST("encrypted-disk");
DO_TEST("memtune");
DO_TEST("blkiotune");
DO_TEST("smp");
/* These tests generate different XML */
DO_TEST_DIFFERENT("balloon-device-auto");
DO_TEST_DIFFERENT("channel-virtio-auto");
DO_TEST_DIFFERENT("console-compat-auto");
DO_TEST_DIFFERENT("disk-scsi-device-auto");
DO_TEST_DIFFERENT("console-virtio");
virCapabilitiesFree(driver.caps);
return (ret==0 ? EXIT_SUCCESS : EXIT_FAILURE);
}
VIRT_TEST_MAIN(mymain)
#else
int main (void) { exit (EXIT_AM_SKIP); }
#endif /* WITH_QEMU */