Re: [Xen-devel] [PATCH 1/5] xen/swiotlb: Simplify the logic.

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Thu, 16 Aug 2012, Konrad Rzeszutek Wilk wrote:
> Its pretty easy:
>  1). We only check to see if we need Xen SWIOTLB for PV guests.
>  2). If swiotlb=force or iommu=soft is set, then Xen SWIOTLB will
>      be enabled.
>  3). If it is an initial domain, then Xen SWIOTLB will be enabled.
>  4). Native SWIOTLB must be disabled for PV guests.
> 
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>

Acked-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>


>  arch/x86/xen/pci-swiotlb-xen.c |    9 +++++----
>  1 files changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/xen/pci-swiotlb-xen.c b/arch/x86/xen/pci-swiotlb-xen.c
> index 967633a..b6a5340 100644
> --- a/arch/x86/xen/pci-swiotlb-xen.c
> +++ b/arch/x86/xen/pci-swiotlb-xen.c
> @@ -34,19 +34,20 @@ static struct dma_map_ops xen_swiotlb_dma_ops = {
>  int __init pci_xen_swiotlb_detect(void)
>  {
>  
> +     if (!xen_pv_domain())
> +             return 0;
> +
>       /* If running as PV guest, either iommu=soft, or swiotlb=force will
>        * activate this IOMMU. If running as PV privileged, activate it
>        * irregardless.
>        */
> -     if ((xen_initial_domain() || swiotlb || swiotlb_force) &&
> -         (xen_pv_domain()))
> +     if ((xen_initial_domain() || swiotlb || swiotlb_force))
>               xen_swiotlb = 1;
>  
>       /* If we are running under Xen, we MUST disable the native SWIOTLB.
>        * Don't worry about swiotlb_force flag activating the native, as
>        * the 'swiotlb' flag is the only one turning it on. */
> -     if (xen_pv_domain())
> -             swiotlb = 0;
> +     swiotlb = 0;
>  
>       return xen_swiotlb;
>  }
> -- 
> 1.7.7.6
> 
> 
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> 

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