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authorEric B Munson <emunson@mgebm.net>2012-03-10 14:37:27 -0500
committerAvi Kivity <avi@redhat.com>2012-04-08 12:49:01 +0300
commit1c0b28c2a46d98cd258d96b8c222144b22876c46 (patch)
tree68c5b4f6a74e3b245dd994752fdc9005075b485c /Documentation/virtual
parent3b5d56b9317fa7b5407dff1aa7b115bf6cdbd494 (diff)
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>
Diffstat (limited to 'Documentation/virtual')
-rw-r--r--Documentation/virtual/kvm/api.txt20
-rw-r--r--Documentation/virtual/kvm/msr.txt4
2 files changed, 24 insertions, 0 deletions
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 6386f8c0482..81ff39f6248 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -1669,6 +1669,26 @@ 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 50317809113..96b41bd9752 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.