KVM: s390: host STP toleration for VMs
If the host has STP enabled, the TOD of the host will be changed during
synchronization phases. These are performed during a stop_machine() call.
As the guest TOD is based on the host TOD, we have to make sure that:
- no VCPU is in the SIE (implicitly guaranteed via stop_machine())
- manual guest TOD calculations are not affected
"Epoch" is the guest TOD clock delta to the host TOD clock. We have to
adjust that value during the STP synchronization and make sure that code
that accesses the epoch won't get interrupted in between (via disabling
preemption).
Signed-off-by: Fan Zhang <zhangfan@linux.vnet.ibm.com>
Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
diff --git a/arch/s390/include/asm/etr.h b/arch/s390/include/asm/etr.h
index 629b79a..f7e5c36 100644
--- a/arch/s390/include/asm/etr.h
+++ b/arch/s390/include/asm/etr.h
@@ -214,6 +214,9 @@
void etr_switch_to_local(void);
void etr_sync_check(void);
+/* notifier for syncs */
+extern struct atomic_notifier_head s390_epoch_delta_notifier;
+
/* STP interruption parameter */
struct stp_irq_parm {
unsigned int _pad0 : 14;
diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c
index 9e733d9..627887b 100644
--- a/arch/s390/kernel/time.c
+++ b/arch/s390/kernel/time.c
@@ -58,6 +58,9 @@
static DEFINE_PER_CPU(struct clock_event_device, comparators);
+ATOMIC_NOTIFIER_HEAD(s390_epoch_delta_notifier);
+EXPORT_SYMBOL(s390_epoch_delta_notifier);
+
/*
* Scheduler clock - returns current time in nanosec units.
*/
@@ -752,7 +755,7 @@
static int etr_sync_clock(void *data)
{
static int first;
- unsigned long long clock, old_clock, delay, delta;
+ unsigned long long clock, old_clock, clock_delta, delay, delta;
struct clock_sync_data *etr_sync;
struct etr_aib *sync_port, *aib;
int port;
@@ -789,6 +792,9 @@
delay = (unsigned long long)
(aib->edf2.etv - sync_port->edf2.etv) << 32;
delta = adjust_time(old_clock, clock, delay);
+ clock_delta = clock - old_clock;
+ atomic_notifier_call_chain(&s390_epoch_delta_notifier, 0,
+ &clock_delta);
etr_sync->fixup_cc = delta;
fixup_clock_comparator(delta);
/* Verify that the clock is properly set. */
@@ -1526,7 +1532,7 @@
static int stp_sync_clock(void *data)
{
static int first;
- unsigned long long old_clock, delta;
+ unsigned long long old_clock, delta, new_clock, clock_delta;
struct clock_sync_data *stp_sync;
int rc;
@@ -1551,7 +1557,11 @@
old_clock = get_tod_clock();
rc = chsc_sstpc(stp_page, STP_OP_SYNC, 0);
if (rc == 0) {
- delta = adjust_time(old_clock, get_tod_clock(), 0);
+ new_clock = get_tod_clock();
+ delta = adjust_time(old_clock, new_clock, 0);
+ clock_delta = new_clock - old_clock;
+ atomic_notifier_call_chain(&s390_epoch_delta_notifier,
+ 0, &clock_delta);
fixup_clock_comparator(delta);
rc = chsc_sstpi(stp_page, &stp_info,
sizeof(struct stp_sstpi));
diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index a578140..b277d50 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -71,9 +71,13 @@
static int ckc_irq_pending(struct kvm_vcpu *vcpu)
{
+ preempt_disable();
if (!(vcpu->arch.sie_block->ckc <
- get_tod_clock_fast() + vcpu->arch.sie_block->epoch))
+ get_tod_clock_fast() + vcpu->arch.sie_block->epoch)) {
+ preempt_enable();
return 0;
+ }
+ preempt_enable();
return ckc_interrupts_enabled(vcpu);
}
@@ -856,7 +860,9 @@
goto no_timer;
}
+ preempt_disable();
now = get_tod_clock_fast() + vcpu->arch.sie_block->epoch;
+ preempt_enable();
sltime = tod_to_ns(vcpu->arch.sie_block->ckc - now);
/* underflow */
@@ -895,7 +901,9 @@
u64 now, sltime;
vcpu = container_of(timer, struct kvm_vcpu, arch.ckc_timer);
+ preempt_disable();
now = get_tod_clock_fast() + vcpu->arch.sie_block->epoch;
+ preempt_enable();
sltime = tod_to_ns(vcpu->arch.sie_block->ckc - now);
/*
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 924b1ae..4bdb860 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -28,6 +28,7 @@
#include <linux/vmalloc.h>
#include <asm/asm-offsets.h>
#include <asm/lowcore.h>
+#include <asm/etr.h>
#include <asm/pgtable.h>
#include <asm/nmi.h>
#include <asm/switch_to.h>
@@ -138,16 +139,47 @@
static void kvm_gmap_notifier(struct gmap *gmap, unsigned long address);
+/*
+ * This callback is executed during stop_machine(). All CPUs are therefore
+ * temporarily stopped. In order not to change guest behavior, we have to
+ * disable preemption whenever we touch the epoch of kvm and the VCPUs,
+ * so a CPU won't be stopped while calculating with the epoch.
+ */
+static int kvm_clock_sync(struct notifier_block *notifier, unsigned long val,
+ void *v)
+{
+ struct kvm *kvm;
+ struct kvm_vcpu *vcpu;
+ int i;
+ unsigned long long *delta = v;
+
+ list_for_each_entry(kvm, &vm_list, vm_list) {
+ kvm->arch.epoch -= *delta;
+ kvm_for_each_vcpu(i, vcpu, kvm) {
+ vcpu->arch.sie_block->epoch -= *delta;
+ }
+ }
+ return NOTIFY_OK;
+}
+
+static struct notifier_block kvm_clock_notifier = {
+ .notifier_call = kvm_clock_sync,
+};
+
int kvm_arch_hardware_setup(void)
{
gmap_notifier.notifier_call = kvm_gmap_notifier;
gmap_register_ipte_notifier(&gmap_notifier);
+ atomic_notifier_chain_register(&s390_epoch_delta_notifier,
+ &kvm_clock_notifier);
return 0;
}
void kvm_arch_hardware_unsetup(void)
{
gmap_unregister_ipte_notifier(&gmap_notifier);
+ atomic_notifier_chain_unregister(&s390_epoch_delta_notifier,
+ &kvm_clock_notifier);
}
int kvm_arch_init(void *opaque)
@@ -501,11 +533,13 @@
return r;
mutex_lock(&kvm->lock);
+ preempt_disable();
kvm->arch.epoch = gtod - host_tod;
kvm_s390_vcpu_block_all(kvm);
kvm_for_each_vcpu(vcpu_idx, cur_vcpu, kvm)
cur_vcpu->arch.sie_block->epoch = kvm->arch.epoch;
kvm_s390_vcpu_unblock_all(kvm);
+ preempt_enable();
mutex_unlock(&kvm->lock);
VM_EVENT(kvm, 3, "SET: TOD base: 0x%llx\n", gtod);
return 0;
@@ -553,7 +587,9 @@
if (r)
return r;
+ preempt_disable();
gtod = host_tod + kvm->arch.epoch;
+ preempt_enable();
if (copy_to_user((void __user *)attr->addr, >od, sizeof(gtod)))
return -EFAULT;
VM_EVENT(kvm, 3, "QUERY: TOD base: 0x%llx\n", gtod);
@@ -1314,7 +1350,9 @@
void kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu)
{
mutex_lock(&vcpu->kvm->lock);
+ preempt_disable();
vcpu->arch.sie_block->epoch = vcpu->kvm->arch.epoch;
+ preempt_enable();
mutex_unlock(&vcpu->kvm->lock);
if (!kvm_is_ucontrol(vcpu->kvm))
vcpu->arch.gmap = vcpu->kvm->arch.gmap;
diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
index afefa3b..4d21dc4 100644
--- a/arch/s390/kvm/priv.c
+++ b/arch/s390/kvm/priv.c
@@ -57,8 +57,10 @@
val = (val - hostclk) & ~0x3fUL;
mutex_lock(&vcpu->kvm->lock);
+ preempt_disable();
kvm_for_each_vcpu(i, cpup, vcpu->kvm)
cpup->arch.sie_block->epoch = val;
+ preempt_enable();
mutex_unlock(&vcpu->kvm->lock);
kvm_s390_set_psw_cc(vcpu, 0);