On Fri, Apr 04, 2014 at 04:41:11PM +0200, Roger Pau Monne wrote:
> Blkback cannot work properly on auto-translated guests if Xen doesn't
> update the IOMMU when performing grant maps/unmaps, so only attach if
> the newly introduced XENFEAT_hvm_gntmap_supports_iommu is found.
Could you point to the git commit that introduces it in the patch please?
>
> Signed-off-by: Roger Pau Monné <roger....@citrix.com>
> Cc: Konrad Rzeszutek Wilk <konrad.w...@oracle.com>
> Cc: David Vrabel <david.vra...@citrix.com>
> Cc: Boris Ostrovsky <boris.ostrov...@oracle.com>
> ---
> drivers/block/xen-blkback/blkback.c | 12 ++++++++++++
> include/xen/interface/features.h | 6 ++++++
> 2 files changed, 18 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/block/xen-blkback/blkback.c
> b/drivers/block/xen-blkback/blkback.c
> index 64c60ed..4c23ddd 100644
> --- a/drivers/block/xen-blkback/blkback.c
> +++ b/drivers/block/xen-blkback/blkback.c
> @@ -1381,6 +1381,18 @@ static int __init xen_blkif_init(void)
> if (!xen_domain())
> return -ENODEV;
>
> +#ifdef CONFIG_X86
> + if (xen_feature(XENFEAT_auto_translated_physmap) &&
> + !xen_feature(XENFEAT_hvm_gntmap_supports_iommu)) {
> + /*
> + * blkback cannot work properly on auto-translated guests
> + * if grant table mappings don't update the IOMMU entries.
> + */
> + pr_debug(DRV_PFX "Disabling blkback because Xen is missing
> feature XENFEAT_hvm_gntmap_supports_iommu\n");
> + return -ENODEV;
> + }
> +#endif /* CONFIG_X86 */
> +
> rc = xen_blkif_interface_init();
> if (rc)
> goto failed_init;
> diff --git a/include/xen/interface/features.h
> b/include/xen/interface/features.h
> index 131a6cc..d1e0f23 100644
> --- a/include/xen/interface/features.h
> +++ b/include/xen/interface/features.h
> @@ -53,6 +53,12 @@
> /* operation as Dom0 is supported */
> #define XENFEAT_dom0 11
>
> +/*
> + * If set, GNTTABOP_map_grant_ref sets the proper IOMMU mappings so the
> + * resulting mapped page can be used for IO with hardware devices.
> + */
> +#define XENFEAT_hvm_gntmap_supports_iommu 12
> +
> #define XENFEAT_NR_SUBMAPS 1
>
> #endif /* __XEN_PUBLIC_FEATURES_H__ */
> --
> 1.7.7.5 (Apple Git-26)
>
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