Re: [PATCH 2/2] Introduce xen_swiotlb variable that is set when Xen is running.

[Jeremy Fitzhardinge <jeremy@goop.org>]

On 09/24/09 15:43, Konrad Rzeszutek Wilk wrote:
> Having the 'xen_swiotlb' variable enabled causes all of the
> IOMMU's to be disabled (except the Xen-SWIOTLB). It is in
> essence a copy of what swiotlb variable does. However the swiotlb variable
> cannot be used because it would turn on the non-Xen SWIOTLB.
> ---
>  arch/x86/include/asm/dma-mapping.h |    1 +
>  arch/x86/include/asm/xen/swiotlb.h |    4 +++-
>  arch/x86/kernel/amd_iommu_init.c   |    2 +-
>  arch/x86/kernel/aperture_64.c      |    2 +-
>  arch/x86/kernel/pci-calgary_64.c   |    2 +-
>  arch/x86/kernel/pci-dma.c          |    4 ++--
>  arch/x86/kernel/pci-gart_64.c      |    2 +-
>  arch/x86/kernel/pci-swiotlb.c      |    4 ++--
>  arch/x86/xen/pci-swiotlb.c         |    3 +++
>  9 files changed, 15 insertions(+), 9 deletions(-)
>
> diff --git a/arch/x86/include/asm/dma-mapping.h b/arch/x86/include/asm/dma-mapping.h
> index 1c3f943..01ef814 100644
> --- a/arch/x86/include/asm/dma-mapping.h
> +++ b/arch/x86/include/asm/dma-mapping.h
> @@ -12,6 +12,7 @@
>  #include <linux/dma-attrs.h>
>  #include <asm/io.h>
>  #include <asm/swiotlb.h>
> +#include <asm/xen/swiotlb.h>
>  #include <asm-generic/dma-coherent.h>
>  
>  extern dma_addr_t bad_dma_address;
> diff --git a/arch/x86/include/asm/xen/swiotlb.h b/arch/x86/include/asm/xen/swiotlb.h
> index d094f89..fd7e48a 100644
> --- a/arch/x86/include/asm/xen/swiotlb.h
> +++ b/arch/x86/include/asm/xen/swiotlb.h
> @@ -2,9 +2,11 @@
>  #define _ASM_X86_XEN_SWIOTLB_H
>  
>  #ifdef CONFIG_PCI_XEN
> +extern int xen_swiotlb;
>  extern void xen_swiotlb_init(void);
>  #else
> -static void xen_swiotlb_init(void) { }
> +#define xen_swiotlb 0
> +static inline void xen_swiotlb_init(void) { }
>  #endif
>  
>  #endif
> diff --git a/arch/x86/kernel/amd_iommu_init.c b/arch/x86/kernel/amd_iommu_init.c
> index c1b17e9..78ec74b 100644
> --- a/arch/x86/kernel/amd_iommu_init.c
> +++ b/arch/x86/kernel/amd_iommu_init.c
> @@ -1304,7 +1304,7 @@ static int __init early_amd_iommu_detect(struct acpi_table_header *table)
>  
>  void __init amd_iommu_detect(void)
>  {
> -	if (swiotlb || no_iommu || (iommu_detected && !gart_iommu_aperture))
> +	if (swiotlb || xen_swiotlb || no_iommu || (iommu_detected && !gart_iommu_aperture))
>  		return;
>  
>  	if (acpi_table_parse("IVRS", early_amd_iommu_detect) == 0) {
> diff --git a/arch/x86/kernel/aperture_64.c b/arch/x86/kernel/aperture_64.c
> index 676debf..6a50006 100644
> --- a/arch/x86/kernel/aperture_64.c
> +++ b/arch/x86/kernel/aperture_64.c
> @@ -369,7 +369,7 @@ void __init gart_iommu_hole_init(void)
>  	int fix, slot, valid_agp = 0;
>  	int i, node;
>  
> -	if (gart_iommu_aperture_disabled || !fix_aperture ||
> +	if (gart_iommu_aperture_disabled || !fix_aperture || xen_swiotlb ||
>  	    !early_pci_allowed())
>  		return;
>  
> diff --git a/arch/x86/kernel/pci-calgary_64.c b/arch/x86/kernel/pci-calgary_64.c
> index 971a3be..f7b8e1c 100644
> --- a/arch/x86/kernel/pci-calgary_64.c
> +++ b/arch/x86/kernel/pci-calgary_64.c
> @@ -1357,7 +1357,7 @@ void __init detect_calgary(void)
>  	 * if the user specified iommu=off or iommu=soft or we found
>  	 * another HW IOMMU already, bail out.
>  	 */
> -	if (swiotlb || no_iommu || iommu_detected)
> +	if (swiotlb || xen_swiotlb || no_iommu || iommu_detected)
>  		return;
>  
>  	if (!use_calgary)
> diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
> index 6b76948..1101a9f 100644
> --- a/arch/x86/kernel/pci-dma.c
> +++ b/arch/x86/kernel/pci-dma.c
> @@ -122,6 +122,8 @@ void __init pci_iommu_alloc(void)
>  	 * The order of these functions is important for
>  	 * fall-back/fail-over reasons
>  	 */
> +	xen_swiotlb_init();
> +
>  	gart_iommu_hole_init();
>  
>  	detect_calgary();
> @@ -130,8 +132,6 @@ void __init pci_iommu_alloc(void)
>  
>  	amd_iommu_detect();
>  
> -	xen_swiotlb_init();
> -
>  	pci_swiotlb_init();
>  }
>  
> diff --git a/arch/x86/kernel/pci-gart_64.c b/arch/x86/kernel/pci-gart_64.c
> index d2e56b8..f2c9f19 100644
> --- a/arch/x86/kernel/pci-gart_64.c
> +++ b/arch/x86/kernel/pci-gart_64.c
> @@ -730,7 +730,7 @@ void __init gart_iommu_init(void)
>  		(agp_copy_info(agp_bridge, &info) < 0);
>  #endif
>  
> -	if (swiotlb)
> +	if (swiotlb || xen_swiotlb)
>  		return;
>  
>  	/* Did we detect a different HW IOMMU? */
> diff --git a/arch/x86/kernel/pci-swiotlb.c b/arch/x86/kernel/pci-swiotlb.c
> index e8a3501..54a0fa9 100644
> --- a/arch/x86/kernel/pci-swiotlb.c
> +++ b/arch/x86/kernel/pci-swiotlb.c
> @@ -47,10 +47,10 @@ void __init pci_swiotlb_init(void)
>  	/* don't initialize swiotlb if iommu=off (no_iommu=1) */
>  #ifdef CONFIG_X86_64
>  	if ((!iommu_detected && !no_iommu && max_pfn > MAX_DMA32_PFN) ||
> -		iommu_pass_through)
> +		iommu_pass_through || !xen_swiotlb)
>   

This doesn't apply to the xen/dom0/swiotlb-new branch.

>  	       swiotlb = 1;
>  #endif
> -	if (swiotlb_force)
> +	if (swiotlb_force || !xen_swiotlb)
>   

Are you sure this is right?  This will always enable swiotlb if
!xen_swiotlb.

    J