#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt

#include <linux/notifier.h>

#include <xen/xen.h>
#include <xen/xenbus.h>

#include <asm/xen/hypervisor.h>
#include <asm/cpu.h>

static void enable_hotplug_cpu(int cpu)
{
	if (!cpu_present(cpu))
		xen_arch_register_cpu(cpu);

	set_cpu_present(cpu, true);
}

static void disable_hotplug_cpu(int cpu)
{
	if (cpu_online(cpu)) {
		lock_device_hotplug();
		device_offline(get_cpu_device(cpu));
		unlock_device_hotplug();
	}
	if (cpu_present(cpu))
		xen_arch_unregister_cpu(cpu);

	set_cpu_present(cpu, false);
}

static int vcpu_online(unsigned int cpu)
{
	int err;
	char dir[16], state[16];

	sprintf(dir, "cpu/%u", cpu);
	err = xenbus_scanf(XBT_NIL, dir, "availability", "%15s", state);
	if (err != 1) {
		if (!xen_initial_domain())
			pr_err("Unable to read cpu state\n");
		return err;
	}

	if (strcmp(state, "online") == 0)
		return 1;
	else if (strcmp(state, "offline") == 0)
		return 0;

	pr_err("unknown state(%s) on CPU%d\n", state, cpu);
	return -EINVAL;
}
static void vcpu_hotplug(unsigned int cpu)
{
	if (!cpu_possible(cpu))
		return;

	switch (vcpu_online(cpu)) {
	case 1:
		enable_hotplug_cpu(cpu);
		break;
	case 0:
		disable_hotplug_cpu(cpu);
		break;
	default:
		break;
	}
}

static void handle_vcpu_hotplug_event(struct xenbus_watch *watch,
					const char **vec, unsigned int len)
{
	unsigned int cpu;
	char *cpustr;
	const char *node = vec[XS_WATCH_PATH];

	cpustr = strstr(node, "cpu/");
	if (cpustr != NULL) {
		sscanf(cpustr, "cpu/%u", &cpu);
		vcpu_hotplug(cpu);
	}
}

static int setup_cpu_watcher(struct notifier_block *notifier,
			      unsigned long event, void *data)
{
	int cpu;
	static struct xenbus_watch cpu_watch = {
		.node = "cpu",
		.callback = handle_vcpu_hotplug_event};

	(void)register_xenbus_watch(&cpu_watch);

	for_each_possible_cpu(cpu) {
		if (vcpu_online(cpu) == 0) {
			(void)cpu_down(cpu);
			set_cpu_present(cpu, false);
		}
	}

	return NOTIFY_DONE;
}

static int __init setup_vcpu_hotplug_event(void)
{
	static struct notifier_block xsn_cpu = {
		.notifier_call = setup_cpu_watcher };

#ifdef CONFIG_X86
	if (!xen_pv_domain())
#else
	if (!xen_domain())
#endif
		return -ENODEV;

	register_xenstore_notifier(&xsn_cpu);

	return 0;
}

arch_initcall(setup_vcpu_hotplug_event);

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<div class='path'>path: <a href='/cgit.cgi/linux/net-next.git/commit/?id=b5b46c4740aed1538544f0fa849c5b76c7823469'>root</a>/<a href='/cgit.cgi/linux/net-next.git/commit/tools?id=b5b46c4740aed1538544f0fa849c5b76c7823469'>tools</a>/<a href='/cgit.cgi/linux/net-next.git/commit/tools/perf?id=b5b46c4740aed1538544f0fa849c5b76c7823469'>perf</a>/<a href='/cgit.cgi/linux/net-next.git/commit/tools/perf/Documentation?id=b5b46c4740aed1538544f0fa849c5b76c7823469'>Documentation</a>/<a href='/cgit.cgi/linux/net-next.git/commit/tools/perf/Documentation/perf-buildid-cache.txt?id=b5b46c4740aed1538544f0fa849c5b76c7823469'>perf-buildid-cache.txt</a></div><div class='content'><div class='cgit-panel'><b>diff options</b><form method='get'><input type='hidden' name='id' value='b5b46c4740aed1538544f0fa849c5b76c7823469'/><table><tr><td colspan='2'/></tr><tr><td class='label'>context:</td><td class='ctrl'><select name='context' onchange='this.form.submit();'><option value='1'>1</option><option value='2'>2</option><option value='3' selected='selected'>3</option><option value='4'>4</option><option value='5'>5</option><option value='6'>6</option><option value='7'>7</option><option value='8'>8</option><option value='9'>9</option><option value='10'>10</option><option value='15'>15</option><option value='20'>20</option><option value='25'>25</option><option value='30'>30</option><option value='35'>35</option><option value='40'>40</option></select></td></tr><tr><td class='label'>space:</td><td class='ctrl'><select name='ignorews' onchange='this.form.submit();'><option value='0' selected='selected'>include</option><option value='1'>ignore</option></select></td></tr><tr><td class='label'>mode:</td><td class='ctrl'><select name='dt' onchange='this.form.submit();'><option value='0' selected='selected'>unified</option><option value='1'>ssdiff</option><option value='2'>stat only</option></select></td></tr><tr><td/><td class='ctrl'><noscript><input type='submit' value='reload'/></noscript></td></tr></table></form></div><table summary='commit info' class='commit-info'>
<tr><th>author</th><td>Jiri Slaby &lt;jslaby@suse.cz&gt;</td><td class='right'>2017-01-18 14:29:21 +0100</td></tr>
<tr><th>committer</th><td>Ingo Molnar &lt;mingo@kernel.org&gt;</td><td class='right'>2017-01-19 08:39:44 +0100</td></tr>
<tr><th>commit</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/tools/perf/Documentation/perf-buildid-cache.txt?id=b5b46c4740aed1538544f0fa849c5b76c7823469'>b5b46c4740aed1538544f0fa849c5b76c7823469</a> (<a href='/cgit.cgi/linux/net-next.git/patch/tools/perf/Documentation/perf-buildid-cache.txt?id=b5b46c4740aed1538544f0fa849c5b76c7823469'>patch</a>)</td></tr>
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<div class='commit-subject'>objtool: Fix IRET's opcode</div><div class='commit-msg'>The IRET opcode is 0xcf according to the Intel manual and also to objdump of my
vmlinux:

    1ea8:       48 cf                   iretq

Fix the opcode in arch_decode_instruction().

The previous value (0xc5) seems to correspond to LDS.

Signed-off-by: Jiri Slaby &lt;jslaby@suse.cz&gt;
Acked-by: Josh Poimboeuf &lt;jpoimboe@redhat.com&gt;
Cc: Andy Lutomirski &lt;luto@kernel.org&gt;
Cc: Borislav Petkov &lt;bp@alien8.de&gt;
Cc: Brian Gerst &lt;brgerst@gmail.com&gt;
Cc: Denys Vlasenko &lt;dvlasenk@redhat.com&gt;
Cc: H. Peter Anvin &lt;hpa@zytor.com&gt;
Cc: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Cc: Peter Zijlstra &lt;peterz@infradead.org&gt;
Cc: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Link: http://lkml.kernel.org/r/20170118132921.19319-1-jslaby@suse.cz
Signed-off-by: Ingo Molnar &lt;mingo@kernel.org&gt;
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