[Qemu-devel] [PATCH V6] Guest stop notification

[Qemu-devel] [PATCH V6] Guest stop notification

[Eric B Munson]

Often when a guest is stopped from the qemu console, it will report spurious
soft lockup warnings on resume.  There are kernel patches being discussed that
will give the host the ability to tell the guest that it is being stopped and
should ignore the soft lockup warning that generates.  This patch uses the qemu
Notifier system to tell the guest it is about to be stopped.

Signed-off-by: Eric B Munson <emunson@mgebm.net>

Cc: Avi Kivity <avi@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>
Cc: ryanh@linux.vnet.ibm.com
Cc: aliguori@us.ibm.com
Cc: kvm@vger.kernel.org
---
Changes from V5:
 KVM_GUEST_PAUSED is now a per vm ioctl instead of per vcpu

Changes from V4:
 Test if the guest paused capability is available before use

Changes from V3:
 Collapse new state change notification function into existsing function.
 Correct whitespace issues
 Change ioctl name to KVMCLOCK_GUEST_PAUSED
 Use for loop to iterate vpcu's

Changes from V2:
 Move ioctl into hw/kvmclock.c so as other arches can use it as it is
implemented

Changes from V1:
 Remove unnecessary encapsulating function
 hw/kvmclock.c |   12 ++++++++++++
 1 files changed, 12 insertions(+), 0 deletions(-)

diff --git a/hw/kvmclock.c b/hw/kvmclock.c
index 3b9fb20..a30504c 100644
--- a/hw/kvmclock.c
+++ b/hw/kvmclock.c
@@ -18,6 +18,7 @@
 #include "sysbus.h"
 #include "kvm.h"
 #include "kvmclock.h"
+#include "cpu-all.h"
 
 #include <linux/kvm.h>
 #include <linux/kvm_para.h>
@@ -64,10 +65,21 @@ static int kvmclock_post_load(void *opaque, int version_id)
 static void kvmclock_vm_state_change(void *opaque, int running,
                                      RunState state)
 {
+    int ret;
     KVMClockState *s = opaque;
+    int cap_guest_paused = kvm_check_extension(kvm_state, KVM_CAP_GUEST_PAUSED);
 
     if (running) {
         s->clock_valid = false;
+
+        if (!cap_guest_paused) {
+            return;
+        }
+
+        ret = kvm_vm_ioctl(kvm_state, KVMCLOCK_GUEST_PAUSED, 0);
+        if (ret) {
+            fprintf(stderr, "kvmclock_vm_state_change: %s\n", strerror(-ret));
+        }
     }
 }
 
-- 
1.7.5.4

Re: [Qemu-devel] [PATCH V6] Guest stop notification

[Jan Kiszka]

On 2012-01-17 19:07, Eric B Munson wrote:
> Often when a guest is stopped from the qemu console, it will report spurious
> soft lockup warnings on resume.  There are kernel patches being discussed that
> will give the host the ability to tell the guest that it is being stopped and
> should ignore the soft lockup warning that generates.  This patch uses the qemu
> Notifier system to tell the guest it is about to be stopped.
> 
> Signed-off-by: Eric B Munson <emunson@mgebm.net>
> 
> Cc: Avi Kivity <avi@redhat.com>
> Cc: Marcelo Tosatti <mtosatti@redhat.com>
> Cc: Jan Kiszka <jan.kiszka@siemens.com>
> Cc: ryanh@linux.vnet.ibm.com
> Cc: aliguori@us.ibm.com
> Cc: kvm@vger.kernel.org
> ---
> Changes from V5:
>  KVM_GUEST_PAUSED is now a per vm ioctl instead of per vcpu
> 
> Changes from V4:
>  Test if the guest paused capability is available before use
> 
> Changes from V3:
>  Collapse new state change notification function into existsing function.
>  Correct whitespace issues
>  Change ioctl name to KVMCLOCK_GUEST_PAUSED
>  Use for loop to iterate vpcu's
> 
> Changes from V2:
>  Move ioctl into hw/kvmclock.c so as other arches can use it as it is
> implemented
> 
> Changes from V1:
>  Remove unnecessary encapsulating function
>  hw/kvmclock.c |   12 ++++++++++++
>  1 files changed, 12 insertions(+), 0 deletions(-)
> 
> diff --git a/hw/kvmclock.c b/hw/kvmclock.c
> index 3b9fb20..a30504c 100644
> --- a/hw/kvmclock.c
> +++ b/hw/kvmclock.c
> @@ -18,6 +18,7 @@
>  #include "sysbus.h"
>  #include "kvm.h"
>  #include "kvmclock.h"
> +#include "cpu-all.h"

Still needed?

>  
>  #include <linux/kvm.h>
>  #include <linux/kvm_para.h>
> @@ -64,10 +65,21 @@ static int kvmclock_post_load(void *opaque, int version_id)
>  static void kvmclock_vm_state_change(void *opaque, int running,
>                                       RunState state)
>  {
> +    int ret;
>      KVMClockState *s = opaque;
> +    int cap_guest_paused = kvm_check_extension(kvm_state, KVM_CAP_GUEST_PAUSED);
>  
>      if (running) {
>          s->clock_valid = false;
> +
> +        if (!cap_guest_paused) {
> +            return;
> +        }
> +
> +        ret = kvm_vm_ioctl(kvm_state, KVMCLOCK_GUEST_PAUSED, 0);
> +        if (ret) {
> +            fprintf(stderr, "kvmclock_vm_state_change: %s\n", strerror(-ret));
> +        }
>      }
>  }
>  

Looks good otherwise.

Thanks,
Jan

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