This patch extends the CONFIG_HOTPLUG_CPU behavior down into the
hypervisor. Currently when a CPU in Linux is moved offline,
echo 0 > /sys/devices/system/cpu/cpuX/online
the offline cpu yields its slice back to the hypervisor. This patch
adds two SCHEDOPS (vcpu_down/vcpu_up) which set/clear a new VCPU flag,
VCPU_down. The domain_runnable() check now looks at this flag and
subsequently the vcpu is not scheduled when VCPU_down is set.
The patch was built and tested against 20050606 nightly snapshot.
Testing requires DOMU with CONFIG_SMP and CONFIG_HOTPLUG_CPU. Please
apply.
--
Ryan Harper
Software Engineer; Linux Technology Center
IBM Corp., Austin, Tx
(512) 838-9253 T/L: 678-9253
ryanh@xxxxxxxxxx
diffstat output:
linux-2.6.11-xen-sparse/arch/xen/i386/kernel/process.c | 7 +
linux-2.6.11-xen-sparse/arch/xen/i386/kernel/smpboot.c | 4
linux-2.6.11-xen-sparse/include/asm-xen/asm-i386/hypercall.h | 31 +++++++
xen/common/schedule.c | 48 +++++++++++
xen/include/public/xen.h | 3
xen/include/xen/sched.h | 5 -
6 files changed, 96 insertions(+), 2 deletions(-)
Signed-off-by: Ryan Harper <ryanh@xxxxxxxxxx>
---
diff -urN b/linux-2.6.11-xen-sparse/arch/xen/i386/kernel/process.c
c/linux-2.6.11-xen-sparse/arch/xen/i386/kernel/process.c
--- b/linux-2.6.11-xen-sparse/arch/xen/i386/kernel/process.c 2005-06-05
22:09:07.000000000 -0500
+++ c/linux-2.6.11-xen-sparse/arch/xen/i386/kernel/process.c 2005-06-06
15:15:34.184156730 -0500
@@ -154,8 +154,13 @@
cpu_clear(cpu, cpu_idle_map);
rmb();
- if (cpu_is_offline(cpu))
+ if (cpu_is_offline(cpu)) {
+#if defined(CONFIG_XEN) && defined(CONFIG_HOTPLUG_CPU)
+ /* Tell hypervisor not to schedule dead vcpus */
+ HYPERVISOR_vcpu_down(cpu);
+#endif
play_dead();
+ }
irq_stat[cpu].idle_timestamp = jiffies;
xen_idle();
diff -urN b/linux-2.6.11-xen-sparse/arch/xen/i386/kernel/smpboot.c
c/linux-2.6.11-xen-sparse/arch/xen/i386/kernel/smpboot.c
--- b/linux-2.6.11-xen-sparse/arch/xen/i386/kernel/smpboot.c 2005-06-05
22:09:13.000000000 -0500
+++ c/linux-2.6.11-xen-sparse/arch/xen/i386/kernel/smpboot.c 2005-06-06
15:44:15.988564794 -0500
@@ -1380,6 +1380,10 @@
}
#ifdef CONFIG_HOTPLUG_CPU
+#ifdef CONFIG_XEN
+ /* Tell hypervisor to bring vcpu up */
+ HYPERVISOR_vcpu_up(cpu);
+#endif
/* Already up, and in cpu_quiescent now? */
if (cpu_isset(cpu, smp_commenced_mask)) {
cpu_enable(cpu);
diff -urN b/linux-2.6.11-xen-sparse/include/asm-xen/asm-i386/hypercall.h
c/linux-2.6.11-xen-sparse/include/asm-xen/asm-i386/hypercall.h
--- b/linux-2.6.11-xen-sparse/include/asm-xen/asm-i386/hypercall.h
2005-06-05 22:09:15.000000000 -0500
+++ c/linux-2.6.11-xen-sparse/include/asm-xen/asm-i386/hypercall.h
2005-06-06 14:18:17.414798645 -0500
@@ -517,4 +517,35 @@
return ret;
}
+static inline int
+HYPERVISOR_vcpu_down(
+ int vcpu)
+{
+ int ret;
+ unsigned long ign1;
+ __asm__ __volatile__ (
+ TRAP_INSTR
+ : "=a" (ret), "=b" (ign1)
+ : "0" (__HYPERVISOR_sched_op),
+ "1" (SCHEDOP_vcpu_down | (vcpu << SCHEDOP_vcpushift))
+ : "memory" );
+
+ return ret;
+}
+
+static inline int
+HYPERVISOR_vcpu_up(
+ int vcpu)
+{
+ int ret;
+ unsigned long ign1;
+ __asm__ __volatile__ (
+ TRAP_INSTR
+ : "=a" (ret), "=b" (ign1)
+ : "0" (__HYPERVISOR_sched_op),
+ "1" (SCHEDOP_vcpu_up | (vcpu << SCHEDOP_vcpushift))
+ : "memory" );
+
+ return ret;
+}
#endif /* __HYPERCALL_H__ */
diff -urN b/xen/common/schedule.c c/xen/common/schedule.c
--- b/xen/common/schedule.c 2005-06-05 22:09:14.000000000 -0500
+++ c/xen/common/schedule.c 2005-06-06 15:50:35.549218230 -0500
@@ -261,6 +261,44 @@
return 0;
}
+/* Mark target vcpu as non-runnable so it is not scheduled */
+static long do_vcpu_down(int vcpu)
+{
+ struct vcpu *target;
+
+ if (vcpu > MAX_VIRT_CPUS)
+ return -EINVAL;
+
+ target = current->domain->vcpu[vcpu];
+ /* DEBUG
+ * printk("DOM%d VCPU%d going down\n",
+ * target->domain->domain_id, target->vcpu_id);
+ */
+ set_bit(_VCPUF_down, &target->vcpu_flags);
+
+ return 0;
+}
+
+/* Mark target vcpu as runnable and wake it */
+static long do_vcpu_up(int vcpu)
+{
+ struct vcpu *target;
+
+ if (vcpu > MAX_VIRT_CPUS)
+ return -EINVAL;
+
+ target = current->domain->vcpu[vcpu];
+ /* DEBUG
+ * printk("DOM%d VCPU%d coming up\n",
+ * target->domain->domain_id, target->vcpu_id);
+ */
+ clear_bit(_VCPUF_down, &target->vcpu_flags);
+ /* wake vcpu */
+ domain_wake(target);
+
+ return 0;
+}
+
/*
* Demultiplex scheduler-related hypercalls.
*/
@@ -290,6 +328,16 @@
domain_shutdown((u8)(op >> SCHEDOP_reasonshift));
break;
}
+ case SCHEDOP_vcpu_down:
+ {
+ ret = do_vcpu_down((int)(op >> SCHEDOP_vcpushift));
+ break;
+ }
+ case SCHEDOP_vcpu_up:
+ {
+ ret = do_vcpu_up((int)(op >> SCHEDOP_vcpushift));
+ break;
+ }
default:
ret = -ENOSYS;
diff -urN b/xen/include/public/xen.h c/xen/include/public/xen.h
--- b/xen/include/public/xen.h 2005-06-05 22:09:13.000000000 -0500
+++ c/xen/include/public/xen.h 2005-06-06 14:18:17.427796825 -0500
@@ -200,8 +200,11 @@
#define SCHEDOP_yield 0 /* Give up the CPU voluntarily. */
#define SCHEDOP_block 1 /* Block until an event is received. */
#define SCHEDOP_shutdown 2 /* Stop executing this domain. */
+#define SCHEDOP_vcpu_down 3 /* make target VCPU not-runnable. */
+#define SCHEDOP_vcpu_up 4 /* make target VCPU runnable. */
#define SCHEDOP_cmdmask 255 /* 8-bit command. */
#define SCHEDOP_reasonshift 8 /* 8-bit reason code. (SCHEDOP_shutdown) */
+#define SCHEDOP_vcpushift 8 /* 8-bit VCPU target. (SCHEDOP_up|down) */
/*
* Reason codes for SCHEDOP_shutdown. These may be interpreted by control
diff -urN b/xen/include/xen/sched.h c/xen/include/xen/sched.h
--- b/xen/include/xen/sched.h 2005-06-05 22:09:08.000000000 -0500
+++ c/xen/include/xen/sched.h 2005-06-06 14:18:17.000000000 -0500
@@ -346,6 +346,9 @@
/* Initialization completed. */
#define _VCPUF_initialised 8
#define VCPUF_initialised (1UL<<_VCPUF_initialised)
+ /* VCPU is not-runnable */
+#define _VCPUF_down 9
+#define VCPUF_down (1UL<<_VCPUF_down)
/*
* Per-domain flags (domain_flags).
@@ -375,7 +378,7 @@
static inline int domain_runnable(struct vcpu *v)
{
return ( (atomic_read(&v->pausecnt) == 0) &&
- !(v->vcpu_flags & (VCPUF_blocked|VCPUF_ctrl_pause)) &&
+ !(v->vcpu_flags & (VCPUF_blocked|VCPUF_ctrl_pause|VCPUF_down)) &&
!(v->domain->domain_flags & (DOMF_shutdown|DOMF_shuttingdown)) );
}
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