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Subject[PATCH 3/4 V15] Add ioctl for KVM_KVMCLOCK_CTRL
Date
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>

Cc: mingo@redhat.com
Cc: hpa@zytor.com
Cc: ryanh@linux.vnet.ibm.com
Cc: aliguori@us.ibm.com
Cc: mtosatti@redhat.com
Cc: kvm@vger.kernel.org
Cc: linux-arch@vger.kernel.org
Cc: x86@kernel.org
Cc: linux-kernel@vger.kernel.org
---
Changes from V14:
Add description of flags bit used for host->guest communication
Changes from V13:
Expand the ioctl documentation
Changes from V12:
Rename KVM_CAP and KVM ioctl
Changes from V11:
Correct typo in api.txt
Add kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu) call to kvm_set_guest_paused()
Changes from V10:
Return the ioctl to per vcpu instead of per vm
Changes from V9:
Use kvm_for_each_vcpu to iterate online vcpu's
Changes from V8:
Make KVM_GUEST_PAUSED a per vm ioctl instead of per vcpu
Changes from V7:
Define KVM_CAP_GUEST_PAUSED and support check
Call mark_page_dirty () after setting PVCLOCK_GUEST_STOPPED
Changes from V4:
Rename KVM_GUEST_PAUSED to KVMCLOCK_GUEST_PAUSED
Add new ioctl description to api.txt

Documentation/virtual/kvm/api.txt | 20 ++++++++++++++++++++
Documentation/virtual/kvm/msr.txt | 4 ++++
arch/x86/kvm/x86.c | 22 ++++++++++++++++++++++
include/linux/kvm.h | 3 +++
4 files changed, 49 insertions(+), 0 deletions(-)

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 59a3826..c9617b3 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -1628,6 +1628,26 @@ at the memory location pointed to by "addr".
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 @@ MSR_KVM_SYSTEM_TIME_NEW: 0x4b564d01
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 c9d99e5..7ba8213 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2143,6 +2143,7 @@ int kvm_dev_ioctl_check_extension(long ext)
case KVM_CAP_XSAVE:
case KVM_CAP_ASYNC_PF:
case KVM_CAP_GET_TSC_KHZ:
+ case KVM_CAP_KVMCLOCK_CTRL:
r = 1;
break;
case KVM_CAP_COALESCED_MMIO:
@@ -2593,6 +2594,23 @@ static int kvm_vcpu_ioctl_x86_set_xcrs(struct kvm_vcpu *vcpu,
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)
{
@@ -2869,6 +2887,10 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
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 acbe429..a90db11 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -588,6 +588,7 @@ struct kvm_ppc_pvinfo {
#define KVM_CAP_TSC_DEADLINE_TIMER 72
#define KVM_CAP_S390_UCONTROL 73
#define KVM_CAP_SYNC_REGS 74
+#define KVM_CAP_KVMCLOCK_CTRL 75

#ifdef KVM_CAP_IRQ_ROUTING

@@ -855,6 +856,8 @@ struct kvm_s390_ucas_mapping {
/* 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)

--
1.7.5.4


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