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Subject[PATCH 10 of 12] xen: implement save/restore
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This patch implements Xen save/restore and migration.

Saving is triggered via xenbus, which is polled in
drivers/xen/manage.c. When a suspend request comes in, the kernel
prepares itself for saving by:

1 - Freeze all processes. This is primarily to prevent any
partially-completed pagetable updates from confusing the suspend
process. If CONFIG_PREEMPT isn't defined, then this isn't necessary.

2 - Suspend xenbus and other devices

3 - Stop_machine, to make sure all the other vcpus are quiescent. The
Xen tools require the domain to run its save off vcpu0.

4 - Within the stop_machine state, it pins any unpinned pgds (under
construction or destruction), performs canonicalizes various other
pieces of state (mostly converting mfns to pfns), and finally

5 - Suspend the domain

Restore reverses the steps used to save the domain, ending when all
the frozen processes are thawed.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
---
arch/x86/xen/Makefile | 2
arch/x86/xen/enlighten.c | 6 +-
arch/x86/xen/mmu.c | 46 ++++++++++++++++
arch/x86/xen/smp.c | 2
arch/x86/xen/suspend.c | 42 ++++++++++++++
arch/x86/xen/time.c | 8 ++
arch/x86/xen/xen-ops.h | 4 +
drivers/xen/events.c | 83 +++++++++++++++++++++++++++++
drivers/xen/grant-table.c | 4 -
drivers/xen/manage.c | 124 +++++++++++++++++++++++++++++++++++++++-----
include/linux/page-flags.h | 1
include/xen/events.h | 3 +
include/xen/grant_table.h | 3 +
include/xen/xen-ops.h | 9 +++
14 files changed, 317 insertions(+), 20 deletions(-)
diff --git a/arch/x86/xen/Makefile b/arch/x86/xen/Makefile
--- a/arch/x86/xen/Makefile
+++ b/arch/x86/xen/Makefile
@@ -1,4 +1,4 @@
obj-y := enlighten.o setup.o multicalls.o mmu.o \
- time.o xen-asm.o grant-table.o
+ time.o xen-asm.o grant-table.o suspend.o

obj-$(CONFIG_SMP) += smp.o
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -857,7 +857,7 @@
PFN_DOWN(__pa(xen_start_info->pt_base)));
}

-static __init void setup_shared_info(void)
+void xen_setup_shared_info(void)
{
if (!xen_feature(XENFEAT_auto_translated_physmap)) {
unsigned long addr = fix_to_virt(FIX_PARAVIRT_BOOTMAP);
@@ -894,7 +894,7 @@
pv_mmu_ops.release_pmd = xen_release_pmd;
pv_mmu_ops.set_pte = xen_set_pte;

- setup_shared_info();
+ xen_setup_shared_info();

/* Actually pin the pagetable down, but we can't set PG_pinned
yet because the page structures don't exist yet. */
@@ -902,7 +902,7 @@
}

/* This is called once we have the cpu_possible_map */
-void __init xen_setup_vcpu_info_placement(void)
+void xen_setup_vcpu_info_placement(void)
{
int cpu;

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -560,6 +560,29 @@
xen_mc_issue(0);
}

+/*
+ * On save, we need to pin all pagetables to make sure they get their
+ * mfns turned into pfns. Search the list for any unpinned pgds and pin
+ * them (unpinned pgds are not currently in use, probably because the
+ * process is under construction or destruction).
+ */
+void xen_mm_pin_all(void)
+{
+ unsigned long flags;
+ struct page *page;
+
+ spin_lock_irqsave(&pgd_lock, flags);
+
+ list_for_each_entry(page, &pgd_list, lru) {
+ if (!PagePinned(page)) {
+ xen_pgd_pin((pgd_t *)page_address(page));
+ SetPageSavePinned(page);
+ }
+ }
+
+ spin_unlock_irqrestore(&pgd_lock, flags);
+}
+
/* The init_mm pagetable is really pinned as soon as its created, but
that's before we have page structures to store the bits. So do all
the book-keeping now. */
@@ -615,6 +638,29 @@
pgd_walk(pgd, unpin_page, TASK_SIZE);

xen_mc_issue(0);
+}
+
+/*
+ * On resume, undo any pinning done at save, so that the rest of the
+ * kernel doesn't see any unexpected pinned pagetables.
+ */
+void xen_mm_unpin_all(void)
+{
+ unsigned long flags;
+ struct page *page;
+
+ spin_lock_irqsave(&pgd_lock, flags);
+
+ list_for_each_entry(page, &pgd_list, lru) {
+ if (PageSavePinned(page)) {
+ BUG_ON(!PagePinned(page));
+ printk("unpinning pinned %p\n", page_address(page));
+ xen_pgd_unpin((pgd_t *)page_address(page));
+ ClearPageSavePinned(page);
+ }
+ }
+
+ spin_unlock_irqrestore(&pgd_lock, flags);
}

void xen_activate_mm(struct mm_struct *prev, struct mm_struct *next)
diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -35,7 +35,7 @@
#include "xen-ops.h"
#include "mmu.h"

-static cpumask_t xen_cpu_initialized_map;
+cpumask_t xen_cpu_initialized_map;
static DEFINE_PER_CPU(int, resched_irq) = -1;
static DEFINE_PER_CPU(int, callfunc_irq) = -1;
static DEFINE_PER_CPU(int, debug_irq) = -1;
diff --git a/arch/x86/xen/suspend.c b/arch/x86/xen/suspend.c
new file mode 100644
--- /dev/null
+++ b/arch/x86/xen/suspend.c
@@ -0,0 +1,42 @@
+#include <linux/types.h>
+
+#include <xen/interface/xen.h>
+#include <xen/grant_table.h>
+#include <xen/events.h>
+
+#include <asm/xen/hypercall.h>
+#include <asm/xen/page.h>
+
+#include "xen-ops.h"
+#include "mmu.h"
+
+void xen_pre_suspend(void)
+{
+ xen_start_info->store_mfn = mfn_to_pfn(xen_start_info->store_mfn);
+ xen_start_info->console.domU.mfn =
+ mfn_to_pfn(xen_start_info->console.domU.mfn);
+
+ BUG_ON(!irqs_disabled());
+
+ HYPERVISOR_shared_info = &xen_dummy_shared_info;
+ if (HYPERVISOR_update_va_mapping(fix_to_virt(FIX_PARAVIRT_BOOTMAP),
+ __pte_ma(0), 0))
+ BUG();
+}
+
+void xen_post_suspend(int suspend_cancelled)
+{
+ if (suspend_cancelled) {
+ xen_start_info->store_mfn =
+ pfn_to_mfn(xen_start_info->store_mfn);
+ xen_start_info->console.domU.mfn =
+ pfn_to_mfn(xen_start_info->console.domU.mfn);
+ } else {
+#ifdef CONFIG_SMP
+ xen_cpu_initialized_map = cpu_online_map;
+#endif
+ }
+
+ xen_setup_shared_info();
+}
+
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -565,6 +565,14 @@
clockevents_register_device(&__get_cpu_var(xen_clock_events));
}

+void xen_time_suspend(void)
+{
+}
+
+void xen_time_resume(void)
+{
+}
+
__init void xen_time_init(void)
{
int cpu = smp_processor_id();
diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -9,6 +9,7 @@
extern const char xen_hypervisor_callback[];
extern const char xen_failsafe_callback[];

+struct trap_info;
void xen_copy_trap_info(struct trap_info *traps);

DECLARE_PER_CPU(unsigned long, xen_cr3);
@@ -19,6 +20,7 @@
extern struct shared_info *HYPERVISOR_shared_info;

void xen_setup_mfn_list_list(void);
+void xen_setup_shared_info(void);

char * __init xen_memory_setup(void);
void __init xen_arch_setup(void);
@@ -59,6 +61,8 @@
int xen_smp_call_function_mask(cpumask_t mask, void (*func)(void *),
void *info, int wait);

+extern cpumask_t xen_cpu_initialized_map;
+

/* Declare an asm function, along with symbols needed to make it
inlineable */
diff --git a/drivers/xen/events.c b/drivers/xen/events.c
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -674,6 +674,89 @@
return ret;
}

+static void restore_cpu_virqs(unsigned int cpu)
+{
+ struct evtchn_bind_virq bind_virq;
+ int virq, irq, evtchn;
+
+ for (virq = 0; virq < NR_VIRQS; virq++) {
+ if ((irq = per_cpu(virq_to_irq, cpu)[virq]) == -1)
+ continue;
+
+ BUG_ON(irq_info[irq].type != IRQT_VIRQ);
+ BUG_ON(irq_info[irq].index != virq);
+
+ /* Get a new binding from Xen. */
+ bind_virq.virq = virq;
+ bind_virq.vcpu = cpu;
+ if (HYPERVISOR_event_channel_op(EVTCHNOP_bind_virq,
+ &bind_virq) != 0)
+ BUG();
+ evtchn = bind_virq.port;
+
+ /* Record the new mapping. */
+ evtchn_to_irq[evtchn] = irq;
+ irq_info[irq] = mk_irq_info(IRQT_VIRQ, virq, evtchn);
+ bind_evtchn_to_cpu(evtchn, cpu);
+
+ /* Ready for use. */
+ unmask_evtchn(evtchn);
+ }
+}
+
+static void restore_cpu_ipis(unsigned int cpu)
+{
+ struct evtchn_bind_ipi bind_ipi;
+ int ipi, irq, evtchn;
+
+ for (ipi = 0; ipi < XEN_NR_IPIS; ipi++) {
+ if ((irq = per_cpu(ipi_to_irq, cpu)[ipi]) == -1)
+ continue;
+
+ BUG_ON(irq_info[irq].type != IRQT_IPI);
+ BUG_ON(irq_info[irq].index != ipi);
+
+ /* Get a new binding from Xen. */
+ bind_ipi.vcpu = cpu;
+ if (HYPERVISOR_event_channel_op(EVTCHNOP_bind_ipi,
+ &bind_ipi) != 0)
+ BUG();
+ evtchn = bind_ipi.port;
+
+ /* Record the new mapping. */
+ evtchn_to_irq[evtchn] = irq;
+ irq_info[irq] = mk_irq_info(IRQT_IPI, ipi, evtchn);
+ bind_evtchn_to_cpu(evtchn, cpu);
+
+ /* Ready for use. */
+ unmask_evtchn(evtchn);
+
+ }
+}
+
+void xen_irq_resume(void)
+{
+ unsigned int cpu, irq, evtchn;
+
+ init_evtchn_cpu_bindings();
+
+ /* New event-channel space is not 'live' yet. */
+ for (evtchn = 0; evtchn < NR_EVENT_CHANNELS; evtchn++)
+ mask_evtchn(evtchn);
+
+ /* No IRQ <-> event-channel mappings. */
+ for (irq = 0; irq < NR_IRQS; irq++)
+ irq_info[irq].evtchn = 0; /* zap event-channel binding */
+
+ for (evtchn = 0; evtchn < NR_EVENT_CHANNELS; evtchn++)
+ evtchn_to_irq[evtchn] = -1;
+
+ for_each_possible_cpu(cpu) {
+ restore_cpu_virqs(cpu);
+ restore_cpu_ipis(cpu);
+ }
+}
+
static struct irq_chip xen_dynamic_chip __read_mostly = {
.name = "xen-dyn",
.mask = disable_dynirq,
diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -471,14 +471,14 @@
return 0;
}

-static int gnttab_resume(void)
+int gnttab_resume(void)
{
if (max_nr_grant_frames() < nr_grant_frames)
return -ENOSYS;
return gnttab_map(0, nr_grant_frames - 1);
}

-static int gnttab_suspend(void)
+int gnttab_suspend(void)
{
arch_gnttab_unmap_shared(shared, nr_grant_frames);
return 0;
diff --git a/drivers/xen/manage.c b/drivers/xen/manage.c
--- a/drivers/xen/manage.c
+++ b/drivers/xen/manage.c
@@ -5,21 +5,113 @@
#include <linux/err.h>
#include <linux/reboot.h>
#include <linux/sysrq.h>
+#include <linux/stop_machine.h>
+#include <linux/freezer.h>

#include <xen/xenbus.h>
+#include <xen/grant_table.h>
+#include <xen/events.h>
+#include <xen/hvc-console.h>
+#include <xen/xen-ops.h>

-#define SHUTDOWN_INVALID -1
-#define SHUTDOWN_POWEROFF 0
-#define SHUTDOWN_SUSPEND 2
-/* Code 3 is SHUTDOWN_CRASH, which we don't use because the domain can only
- * report a crash, not be instructed to crash!
- * HALT is the same as POWEROFF, as far as we're concerned. The tools use
- * the distinction when we return the reason code to them.
- */
-#define SHUTDOWN_HALT 4
+#include <asm/xen/hypercall.h>
+#include <asm/xen/page.h>
+
+enum shutdown_state {
+ SHUTDOWN_INVALID = -1,
+ SHUTDOWN_POWEROFF = 0,
+ SHUTDOWN_SUSPEND = 2,
+ /* Code 3 is SHUTDOWN_CRASH, which we don't use because the domain can only
+ report a crash, not be instructed to crash!
+ HALT is the same as POWEROFF, as far as we're concerned. The tools use
+ the distinction when we return the reason code to them. */
+ SHUTDOWN_HALT = 4,
+};

/* Ignore multiple shutdown requests. */
-static int shutting_down = SHUTDOWN_INVALID;
+static enum shutdown_state shutting_down = SHUTDOWN_INVALID;
+
+static int xen_suspend(void *data)
+{
+ int *cancelled = data;
+
+ BUG_ON(!irqs_disabled());
+
+ load_cr3(swapper_pg_dir);
+
+ xen_mm_pin_all();
+ gnttab_suspend();
+ xen_time_suspend();
+ xen_pre_suspend();
+
+ /*
+ * This hypercall returns 1 if suspend was cancelled
+ * or the domain was merely checkpointed, and 0 if it
+ * is resuming in a new domain.
+ */
+ *cancelled = HYPERVISOR_suspend(virt_to_mfn(xen_start_info));
+
+ xen_post_suspend(*cancelled);
+ xen_time_resume();
+ gnttab_resume();
+ xen_mm_unpin_all();
+
+ if (!*cancelled) {
+ xen_irq_resume();
+ xen_console_resume();
+ }
+
+ return 0;
+}
+
+static void do_suspend(void)
+{
+ int err;
+ int cancelled = 1;
+
+ shutting_down = SHUTDOWN_SUSPEND;
+
+#ifdef CONFIG_PREEMPT
+ /* If the kernel is preemptible, we need to freeze all the processes
+ to prevent them from being in the middle of a pagetable update
+ during suspend. */
+ err = freeze_processes();
+ if (err) {
+ printk(KERN_ERR "xen suspend: freeze failed %d\n", err);
+ return;
+ }
+#endif
+
+ err = device_suspend(PMSG_SUSPEND);
+ if (err) {
+ printk(KERN_ERR "xen suspend: device_suspend %d\n", err);
+ goto out;
+ }
+
+ printk("suspending xenbus...\n");
+ /* XXX use normal device tree? */
+ xenbus_suspend();
+
+ err = stop_machine_run(xen_suspend, &cancelled, 0);
+ if (err) {
+ printk(KERN_ERR "failed to start xen_suspend: %d\n", err);
+ goto out;
+ }
+
+ if (!cancelled)
+ xenbus_resume();
+ else
+ xenbus_suspend_cancel();
+
+ device_resume();
+
+
+out:
+#ifdef CONFIG_PREEMPT
+ thaw_processes();
+#endif
+ shutting_down = SHUTDOWN_INVALID;
+}

static void shutdown_handler(struct xenbus_watch *watch,
const char **vec, unsigned int len)
@@ -52,11 +144,17 @@
}

if (strcmp(str, "poweroff") == 0 ||
- strcmp(str, "halt") == 0)
+ strcmp(str, "halt") == 0) {
+ shutting_down = SHUTDOWN_POWEROFF;
orderly_poweroff(false);
- else if (strcmp(str, "reboot") == 0)
+ } else if (strcmp(str, "reboot") == 0) {
+ shutting_down = SHUTDOWN_POWEROFF; /* ? */
ctrl_alt_del();
- else {
+#ifdef CONFIG_PM_SLEEP
+ } else if (strcmp(str, "suspend") == 0) {
+ do_suspend();
+#endif
+ } else {
printk(KERN_INFO "Ignoring shutdown request: %s\n", str);
shutting_down = SHUTDOWN_INVALID;
}
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -157,6 +157,7 @@
__PAGEFLAG(Slab, slab)
PAGEFLAG(Checked, owner_priv_1) /* Used by some filesystems */
PAGEFLAG(Pinned, owner_priv_1) TESTSCFLAG(Pinned, owner_priv_1) /* Xen */
+PAGEFLAG(SavePinned, dirty); /* Xen */
PAGEFLAG(Reserved, reserved) __CLEARPAGEFLAG(Reserved, reserved)
PAGEFLAG(Private, private) __CLEARPAGEFLAG(Private, private)
__SETPAGEFLAG(Private, private)
diff --git a/include/xen/events.h b/include/xen/events.h
--- a/include/xen/events.h
+++ b/include/xen/events.h
@@ -41,4 +41,7 @@
}

extern void notify_remote_via_irq(int irq);
+
+extern void xen_irq_resume(void);
+
#endif /* _XEN_EVENTS_H */
diff --git a/include/xen/grant_table.h b/include/xen/grant_table.h
--- a/include/xen/grant_table.h
+++ b/include/xen/grant_table.h
@@ -50,6 +50,9 @@
void *arg;
u16 count;
};
+
+int gnttab_suspend(void);
+int gnttab_resume(void);

int gnttab_grant_foreign_access(domid_t domid, unsigned long frame,
int readonly);
diff --git a/include/xen/xen-ops.h b/include/xen/xen-ops.h
--- a/include/xen/xen-ops.h
+++ b/include/xen/xen-ops.h
@@ -5,4 +5,13 @@

DECLARE_PER_CPU(struct vcpu_info *, xen_vcpu);

+void xen_pre_suspend(void);
+void xen_post_suspend(int suspend_cancelled);
+
+void xen_mm_pin_all(void);
+void xen_mm_unpin_all(void);
+
+void xen_time_suspend(void);
+void xen_time_resume(void);
+
#endif /* INCLUDE_XEN_OPS_H */



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