On 2012-01-11 19:17, 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@xxxxxxxxx>
>
> Cc: Avi Kivity <avi@xxxxxxxxxx>
> Cc: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
> Cc: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
> Cc: ryanh@xxxxxxxxxxxxxxxxxx
> Cc: aliguori@xxxxxxxxxx
> Cc: kvm@xxxxxxxxxxxxxxx
> ---
> 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 | 20 ++++++++++++++++++++
> 1 files changed, 20 insertions(+), 0 deletions(-)
>
> diff --git a/hw/kvmclock.c b/hw/kvmclock.c
> index 5388bc4..d071d61 100644
> --- a/hw/kvmclock.c
> +++ b/hw/kvmclock.c
> @@ -16,6 +16,7 @@
> #include "sysbus.h"
> #include "kvm.h"
> #include "kvmclock.h"
> +#include "cpu-all.h"
>
> #include <linux/kvm.h>
> #include <linux/kvm_para.h>
> @@ -62,10 +63,29 @@ static int kvmclock_post_load(void *opaque, int version_id)
> static void kvmclock_vm_state_change(void *opaque, int running,
> RunState state)
> {
> + int ret;
> + CPUState *penv = first_cpu;
> 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;
> + }
Why? You already ignore -EINVAL.
> +
> + for (penv = first_cpu; penv != NULL; penv = penv->next_cpu) {
> + ret = kvm_vcpu_ioctl(penv, KVMCLOCK_GUEST_PAUSED, 0);
This indicates that the interface could still be improved:
"GUEST_PAUSED" implies to me a VM state, but the IOCTL has to be applied
per VCPU. This is inconsistent.
Why not define a per-VM IOCTL? Would make user space's life a little bit
easier as well.
Or is there a valid use case of selectively paused VCPUs? Then call it
KVMCLOCK_VCPU_PAUSED.
> + if (ret) {
> + if (ret != -EINVAL) {
What is special about -EINVAL (as long as the cap is checked)?
> + fprintf(stderr,
> + "kvmclock_vm_state_change: %s\n",
> + strerror(-ret));
> + }
> + return;
> + }
> + }
> }
> }
>
Jan
--
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux
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