linux-kernel - Re: [PATCH] Guest stop notification

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Message-ID: <4ED79138.60603@siemens.com>
Date:	Thu, 01 Dec 2011 15:37:44 +0100
From:	Jan Kiszka <jan.kiszka@...mens.com>
To:	Eric B Munson <emunson@...bm.net>
CC:	qemu-devel@...gnu.org, ryanh@...ux.vnet.ibm.com,
	aliguori@...ibm.com, kvm@...r.kernel.org, mtosatti@...hat.com,
	linux-kernel@...r.kernel.org, avi@...hat.com
Subject: Re: [PATCH] Guest stop notification

On 2011-11-29 22:36, 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.
> 
> Signed-off-by: Eric B Munson <emunson@...bm.net>
> Cc: ryanh@...ux.vnet.ibm.com
> Cc: aliguori@...ibm.com
> Cc: mtosatti@...hat.com
> Cc: avi@...hat.com
> Cc: kvm@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> ---
>  target-i386/kvm.c |    6 ++++++
>  1 files changed, 6 insertions(+), 0 deletions(-)
> 
> diff --git a/target-i386/kvm.c b/target-i386/kvm.c
> index 5bfc21f..defd364 100644
> --- a/target-i386/kvm.c
> +++ b/target-i386/kvm.c
> @@ -336,12 +336,18 @@ static int kvm_inject_mce_oldstyle(CPUState *env)
>      return 0;
>  }
>  
> +static void kvm_put_guest_paused(CPUState *penv)
> +{
> +    kvm_vcpu_ioctl(penv, KVM_GUEST_PAUSED, 0);
> +}

I see no need in encapsulating this in a separate function.

> +
>  static void cpu_update_state(void *opaque, int running, RunState state)
>  {
>      CPUState *env = opaque;
>  
>      if (running) {
>          env->tsc_valid = false;
> +	kvm_put_guest_paused(env);

checkpatch.pl would have asked you to remove this tab.

More general:

Why is this x86-only? If the kernel interface is x86-only, what prevents
making it generic right from the beginning?

Why do we need a new IOCTL for this? Was there no space left in the
kvm_run structure e.g. to pass this flag down on next vcpu execution? No
big deal, just wondering.

Jan

-- 
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux
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