Re: [Xen-ia64-devel][PATCH][VTD] small patches for VTD

[Isaku Yamahata <yamahata@xxxxxxxxxxxxx>]

On Thu, Oct 23, 2008 at 03:10:55PM +0800, Xu, Anthony wrote:
> The new one,

It looks almost okay. The last one.


> diff -r 02c8733e2d91 xen/arch/ia64/vmx/viosapic.c
> --- a/xen/arch/ia64/vmx/viosapic.c    Wed Oct 22 17:20:15 2008 +0900
> +++ b/xen/arch/ia64/vmx/viosapic.c    Thu Oct 23 14:48:09 2008 +0800
> @@ -121,6 +121,13 @@
>                       redir_num, vector);
>          return;
>      }
> +    if ( iommu_enabled )
> +    {
> +        spin_unlock(&viosapic->lock);
> +        hvm_dpci_eoi(current->domain, redir_num, 
> &viosapic->redirtbl[redir_num]);
> +        spin_lock(&viosapic->lock);
> +    }
> +
>      service_iosapic(viosapic);
>      spin_unlock(&viosapic->lock);
>  }

Is this unlock/lock sequence okay?
I'm asking simply because I'm not sure.

viosapic->irr and isr are protected by the lock.
And viosapic_update_EOI() updates them atomically.
The above unlock/lock seems to break its atomicity.

I'm not sure it's okay or not. To make sure, it is required
to take closer look at viosapic.c.

thanks,
-- 
yamahata

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