KVM: x86: Add ioctl for KVM_KVMCLOCK_CTRL
Now that we have a flag that will tell the guest it was suspended, create an
interface for that communication using a KVM ioctl.
Signed-off-by: Eric B Munson <emunson@mgebm.net>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 6386f8c..81ff39f 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -1669,6 +1669,26 @@
The list of registers accessible using this interface is identical to the
list in 4.64.
+4.70 KVM_KVMCLOCK_CTRL
+
+Capability: KVM_CAP_KVMCLOCK_CTRL
+Architectures: Any that implement pvclocks (currently x86 only)
+Type: vcpu ioctl
+Parameters: None
+Returns: 0 on success, -1 on error
+
+This signals to the host kernel that the specified guest is being paused by
+userspace. The host will set a flag in the pvclock structure that is checked
+from the soft lockup watchdog. The flag is part of the pvclock structure that
+is shared between guest and host, specifically the second bit of the flags
+field of the pvclock_vcpu_time_info structure. It will be set exclusively by
+the host and read/cleared exclusively by the guest. The guest operation of
+checking and clearing the flag must an atomic operation so
+load-link/store-conditional, or equivalent must be used. There are two cases
+where the guest will clear the flag: when the soft lockup watchdog timer resets
+itself or when a soft lockup is detected. This ioctl can be called any time
+after pausing the vcpu, but before it is resumed.
+
5. The kvm_run structure
Application code obtains a pointer to the kvm_run structure by
diff --git a/Documentation/virtual/kvm/msr.txt b/Documentation/virtual/kvm/msr.txt
index 5031780..96b41bd 100644
--- a/Documentation/virtual/kvm/msr.txt
+++ b/Documentation/virtual/kvm/msr.txt
@@ -109,6 +109,10 @@
0 | 24 | multiple cpus are guaranteed to
| | be monotonic
-------------------------------------------------------------
+ | | guest vcpu has been paused by
+ 1 | N/A | the host
+ | | See 4.70 in api.txt
+ -------------------------------------------------------------
Availability of this MSR must be checked via bit 3 in 0x4000001 cpuid
leaf prior to usage.
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 511031d..99b7380 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2147,6 +2147,7 @@
case KVM_CAP_ASYNC_PF:
case KVM_CAP_GET_TSC_KHZ:
case KVM_CAP_PCI_2_3:
+ case KVM_CAP_KVMCLOCK_CTRL:
r = 1;
break;
case KVM_CAP_COALESCED_MMIO:
@@ -2597,6 +2598,23 @@
return r;
}
+/*
+ * kvm_set_guest_paused() indicates to the guest kernel that it has been
+ * stopped by the hypervisor. This function will be called from the host only.
+ * EINVAL is returned when the host attempts to set the flag for a guest that
+ * does not support pv clocks.
+ */
+static int kvm_set_guest_paused(struct kvm_vcpu *vcpu)
+{
+ struct pvclock_vcpu_time_info *src = &vcpu->arch.hv_clock;
+ if (!vcpu->arch.time_page)
+ return -EINVAL;
+ src->flags |= PVCLOCK_GUEST_STOPPED;
+ mark_page_dirty(vcpu->kvm, vcpu->arch.time >> PAGE_SHIFT);
+ kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
+ return 0;
+}
+
long kvm_arch_vcpu_ioctl(struct file *filp,
unsigned int ioctl, unsigned long arg)
{
@@ -2873,6 +2891,10 @@
r = vcpu->arch.virtual_tsc_khz;
goto out;
}
+ case KVM_KVMCLOCK_CTRL: {
+ r = kvm_set_guest_paused(vcpu);
+ goto out;
+ }
default:
r = -EINVAL;
}
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index 6c322a9..7a9dd4b 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -589,6 +589,7 @@
#define KVM_CAP_S390_UCONTROL 73
#define KVM_CAP_SYNC_REGS 74
#define KVM_CAP_PCI_2_3 75
+#define KVM_CAP_KVMCLOCK_CTRL 76
#ifdef KVM_CAP_IRQ_ROUTING
@@ -859,6 +860,8 @@
/* Available with KVM_CAP_ONE_REG */
#define KVM_GET_ONE_REG _IOW(KVMIO, 0xab, struct kvm_one_reg)
#define KVM_SET_ONE_REG _IOW(KVMIO, 0xac, struct kvm_one_reg)
+/* VM is being stopped by host */
+#define KVM_KVMCLOCK_CTRL _IO(KVMIO, 0xad)
#define KVM_DEV_ASSIGN_ENABLE_IOMMU (1 << 0)
#define KVM_DEV_ASSIGN_PCI_2_3 (1 << 1)