Re: [PATCH] qemu-kvm: x86: Fix mismerge in cpu_post_load

[Gleb Natapov <gleb@redhat.com>]

On Thu, Dec 03, 2009 at 07:21:01PM +0100, Jan Kiszka wrote:
> Merge 8e2c5ec2f6 forgot to restore some qemu-kvm-specific hooks in
> cpu_post_load. mp_state was readded later on, but tsc was missing,
> breaking the guest timing after resume. Also, reset of halt was dropped
> which is obviously required for in-kernel irqchip.
> 
> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> ---
> 
> This solves "Problem 1" on my list.
> 
> BTW, this patch just made me realize that the TSC MSR belongs to the
> list states that should not be written back unconditionally. Upstream
> does this currently, qemu-kvm not (at the price one more kvm-specific
> hook into generic code). Unlike the other states we discussed, this one
> is not "fixable" in the kernel. So I tend to think there is a real need
> for my write-back scope abstraction - which would also be able to handle
> the other states cleanly, both in upstream and here.
> 
>  target-i386/machine.c |   10 +++++++++-
>  1 files changed, 9 insertions(+), 1 deletions(-)
> 
> diff --git a/target-i386/machine.c b/target-i386/machine.c
> index 6bd447f..9ac477b 100644
> --- a/target-i386/machine.c
> +++ b/target-i386/machine.c
> @@ -366,7 +366,15 @@ static int cpu_post_load(void *opaque, int version_id)
>          hw_breakpoint_insert(env, i);
>  
>      tlb_flush(env, 1);
> -    kvm_load_mpstate(env);
> +
> +    if (kvm_enabled()) {
> +        /* when in-kernel irqchip is used, env->halted causes deadlock
> +           because no userspace IRQs will ever clear this flag */
> +        env->halted = 0;
> +
That is strange. env->halted should be used only for "info cpus" output
in case of in-kernel irqchip. Can you see where it hangs?

> +        kvm_load_tsc(env);
> +        kvm_load_mpstate(env);
> +    }
>  
>      return 0;
>  }

--
			Gleb.