On Tue, Jul 21, 2009 at 04:01:37PM +0100, Mark McLoughlin wrote:
> In qemu-0.11 there is a 'pc-0.10' machine type which allows you to run
> guests with a machine which is compatible with the pc machine in
> qemu-0.10 - e.g. using the original PCI class for virtio-blk and
> virtio-console and disabling MSI support in virtio-net. The idea here
> is that we don't want to surprise guests by changing the hardware when
> qemu is updated.
>
> I've just posted some patches for qemu-0.11 which allows libvirt to
> canonicalize the 'pc' machine alias to the latest machine version.
>
> This patches makes us use that so that when a guest is configured to
> use the 'pc' machine type, we resolve that to 'pc-0.11' machine and
> save that in the guest XML.
We currently also list "valid" machine types in the capabilities
XML for each driver. I use quotes, because this list is currently
dubiously hardcoded. I'm thinking it might be better to do the
parsing of -M ? output as part of the capaiblities intiialization
code. The canonicalize method would then just need to query the
existing capabilities data & could even be done in the domain XML
parser code instead of qemu driver.
> ---
> src/qemu_conf.c | 114 +++++++++++++++++++++++++++++++++++++++++++++++++++++
> src/qemu_conf.h | 3 +
> src/qemu_driver.c | 3 +
> 3 files changed, 120 insertions(+), 0 deletions(-)
>
> diff --git a/src/qemu_conf.c b/src/qemu_conf.c
> index 4043d70..3f4edfa 100644
> --- a/src/qemu_conf.c
> +++ b/src/qemu_conf.c
> @@ -470,6 +470,120 @@ virCapsPtr qemudCapsInit(void) {
> return NULL;
> }
>
> +/* Format is:
> + * <machine> <desc> [(alias of <machine>)]
> + */
> +static int
> +qemudParseMachineTypesStr(const char *machines ATTRIBUTE_UNUSED,
> + const char *machine ATTRIBUTE_UNUSED,
> + char **canonical)
> +{
> + const char *p = machines;
> +
> + *canonical = NULL;
> +
> + do {
> + const char *eol;
> + char *s;
> +
> + if (!(eol = strchr(p, '\n')))
> + return -1; /* eof file without finding @machine */
> +
> + if (!STRPREFIX(p, machine)) {
> + p = eol + 1;
> + continue; /* doesn't match @machine */
> + }
> +
> + p += strlen(machine);
> +
> + if (*p != ' ') {
> + p = eol + 1;
> + continue; /* not a complete match of @machine */
> + }
> +
> + do {
> + p++;
> + } while (*p == ' ');
> +
> + p = strstr(p, "(alias of ");
> + if (!p || p > eol)
> + return 0; /* not an alias, name is canonical */
> +
> + *canonical = strndup(p + strlen("(alias of "), eol - p);
Need to check for NULL here.
> +
> + s = strchr(*canonical, ')');
> + if (!s) {
> + VIR_FREE(*canonical);
> + *canonical = NULL;
> + return -1; /* output is screwed up */
> + }
> +
> + *s = '\0';
> + break;
> + } while (1);
> +
> + return 0;
> +}
> +
> +int
> +qemudCanonicalizeMachine(virConnectPtr conn ATTRIBUTE_UNUSED,
> + virDomainDefPtr def)
> +{
> + const char *const qemuarg[] = { def->emulator, "-M", "?", NULL };
> + const char *const qemuenv[] = { "LC_ALL=C", NULL };
> + char *machines, *canonical;
> + enum { MAX_MACHINES_OUTPUT_SIZE = 1024*4 };
> + pid_t child;
> + int newstdout = -1, len;
> + int ret = -1, status;
> +
> + if (virExec(NULL, qemuarg, qemuenv, NULL,
> + &child, -1, &newstdout, NULL, VIR_EXEC_CLEAR_CAPS) < 0)
> + return -1;
> +
> + len = virFileReadLimFD(newstdout, MAX_MACHINES_OUTPUT_SIZE, &machines);
> + if (len < 0) {
> + virReportSystemError(NULL, errno, "%s",
> + _("Unable to read 'qemu -M ?' output"));
> + goto cleanup;
> + }
> +
> + if (qemudParseMachineTypesStr(machines, def->os.machine, &canonical) < 0)
> + goto cleanup2;
> +
> + if (canonical) {
> + VIR_FREE(def->os.machine);
> + def->os.machine = canonical;
> + }
> +
> + ret = 0;
> +
> +cleanup2:
> + VIR_FREE(machines);
> +cleanup:
> + if (close(newstdout) < 0)
> + ret = -1;
> +
> +rewait:
> + if (waitpid(child, &status, 0) != child) {
> + if (errno == EINTR)
> + goto rewait;
> +
> + VIR_ERROR(_("Unexpected exit status from qemu %d pid %lu"),
> + WEXITSTATUS(status), (unsigned long)child);
> + ret = -1;
> + }
> + /* Check & log unexpected exit status, but don't fail,
> + * as there's really no need to throw an error if we did
> + * actually read a valid version number above */
> + if (WEXITSTATUS(status) != 0) {
> + VIR_WARN(_("Unexpected exit status '%d', qemu probably failed"),
> + WEXITSTATUS(status));
> + }
> +
> + return ret;
> +}
> +
> static unsigned int qemudComputeCmdFlags(const char *help,
> unsigned int version,
> unsigned int is_kvm,
> diff --git a/src/qemu_conf.h b/src/qemu_conf.h
> index fbf2ab9..b668669 100644
> --- a/src/qemu_conf.h
> +++ b/src/qemu_conf.h
> @@ -123,6 +123,9 @@ int qemudExtractVersionInfo (const char *qemu,
> unsigned int *version,
> unsigned int *flags);
>
> +int qemudCanonicalizeMachine (virConnectPtr conn,
> + virDomainDefPtr def);
> +
> int qemudParseHelpStr (const char *str,
> unsigned int *flags,
> unsigned int *version,
> diff --git a/src/qemu_driver.c b/src/qemu_driver.c
> index d2db1a2..98f8e95 100644
> --- a/src/qemu_driver.c
> +++ b/src/qemu_driver.c
> @@ -4102,6 +4102,9 @@ static virDomainPtr qemudDomainDefine(virConnectPtr conn, const char *xml) {
> }
> }
>
> + if (qemudCanonicalizeMachine(conn, def) < 0)
> + goto cleanup;
> +
> if (!(vm = virDomainAssignDef(conn,
> &driver->domains,
> def))) {
> --
> 1.6.2.5
Daniel
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