qga: implement qmp_guest_get_vcpus() for Linux with sysfs (d2baff62) · Commits · SUMMER2020 / students / proj-2021291

qga/commands-posix.c

+140 −6

Original line number	Diff line number	Diff line
		@@ -15,6 +15,10 @@
		#include <sys/types.h>
		#include <sys/ioctl.h>
		#include <sys/wait.h>
		#include <unistd.h>
		#include <errno.h>
		#include <fcntl.h>
		#include <inttypes.h>
		#include "qga/guest-agent-core.h"
		#include "qga-qmp-commands.h"
		#include "qapi/qmp/qerror.h"
		@@ -1111,6 +1115,136 @@ error:
		return NULL;
		}

		#define SYSCONF_EXACT(name, err) sysconf_exact((name), #name, (err))

		static long sysconf_exact(int name, const char name_str, Error *err)
		{
		long ret;

		errno = 0;
		ret = sysconf(name);
		if (ret == -1) {
		if (errno == 0) {
		error_setg(err, "sysconf(%s): value indefinite", name_str);
		} else {
		error_setg_errno(err, errno, "sysconf(%s)", name_str);
		}
		}
		return ret;
		}

		/* Transfer online/offline status between @vcpu and the guest system.
		*
		* On input either @errp or *@errp must be NULL.
		*
		* In system-to-@vcpu direction, the following @vcpu fields are accessed:
		* - R: vcpu->logical_id
		* - W: vcpu->online
		* - W: vcpu->can_offline
		*
		* In @vcpu-to-system direction, the following @vcpu fields are accessed:
		* - R: vcpu->logical_id
		* - R: vcpu->online
		*
		* Written members remain unmodified on error.
		*/
		static void transfer_vcpu(GuestLogicalProcessor *vcpu, bool sys2vcpu,
		Error **errp)
		{
		char *dirpath;
		int dirfd;

		dirpath = g_strdup_printf("/sys/devices/system/cpu/cpu%" PRId64 "/",
		vcpu->logical_id);
		dirfd = open(dirpath, O_RDONLY \| O_DIRECTORY);
		if (dirfd == -1) {
		error_setg_errno(errp, errno, "open(\"%s\")", dirpath);
		} else {
		static const char fn[] = "online";
		int fd;
		int res;

		fd = openat(dirfd, fn, sys2vcpu ? O_RDONLY : O_RDWR);
		if (fd == -1) {
		if (errno != ENOENT) {
		error_setg_errno(errp, errno, "open(\"%s/%s\")", dirpath, fn);
		} else if (sys2vcpu) {
		vcpu->online = true;
		vcpu->can_offline = false;
		} else if (!vcpu->online) {
		error_setg(errp, "logical processor #%" PRId64 " can't be "
		"offlined", vcpu->logical_id);
		} /* otherwise pretend successful re-onlining */
		} else {
		unsigned char status;

		res = pread(fd, &status, 1, 0);
		if (res == -1) {
		error_setg_errno(errp, errno, "pread(\"%s/%s\")", dirpath, fn);
		} else if (res == 0) {
		error_setg(errp, "pread(\"%s/%s\"): unexpected EOF", dirpath,
		fn);
		} else if (sys2vcpu) {
		vcpu->online = (status != '0');
		vcpu->can_offline = true;
		} else if (vcpu->online != (status != '0')) {
		status = '0' + vcpu->online;
		if (pwrite(fd, &status, 1, 0) == -1) {
		error_setg_errno(errp, errno, "pwrite(\"%s/%s\")", dirpath,
		fn);
		}
		} /* otherwise pretend successful re-(on\|off)-lining */

		res = close(fd);
		g_assert(res == 0);
		}

		res = close(dirfd);
		g_assert(res == 0);
		}

		g_free(dirpath);
		}

		GuestLogicalProcessorList qmp_guest_get_vcpus(Error *errp)
		{
		int64_t current;
		GuestLogicalProcessorList head, *link;
		long sc_max;
		Error *local_err = NULL;

		current = 0;
		head = NULL;
		link = &head;
		sc_max = SYSCONF_EXACT(_SC_NPROCESSORS_CONF, &local_err);

		while (local_err == NULL && current < sc_max) {
		GuestLogicalProcessor *vcpu;
		GuestLogicalProcessorList *entry;

		vcpu = g_malloc0(sizeof *vcpu);
		vcpu->logical_id = current++;
		vcpu->has_can_offline = true; /* lolspeak ftw */
		transfer_vcpu(vcpu, true, &local_err);

		entry = g_malloc0(sizeof *entry);
		entry->value = vcpu;

		*link = entry;
		link = &entry->next;
		}

		if (local_err == NULL) {
		/* there's no guest with zero VCPUs */
		g_assert(head != NULL);
		return head;
		}

		qapi_free_GuestLogicalProcessorList(head);
		error_propagate(errp, local_err);
		return NULL;
		}

		#else /* defined(__linux__) */

		void qmp_guest_suspend_disk(Error **err)
		@@ -1134,6 +1268,12 @@ GuestNetworkInterfaceList qmp_guest_network_get_interfaces(Error *errp)
		return NULL;
		}

		GuestLogicalProcessorList qmp_guest_get_vcpus(Error *errp)
		{
		error_set(errp, QERR_UNSUPPORTED);
		return NULL;
		}

		#endif

		#if !defined(CONFIG_FSFREEZE)
		@@ -1167,12 +1307,6 @@ void qmp_guest_fstrim(bool has_minimum, int64_t minimum, Error **err)
		}
		#endif

		GuestLogicalProcessorList qmp_guest_get_vcpus(Error *errp)
		{
		error_set(errp, QERR_UNSUPPORTED);
		return NULL;
		}

		int64_t qmp_guest_set_vcpus(GuestLogicalProcessorList vcpus, Error *errp)
		{
		error_set(errp, QERR_UNSUPPORTED);