Re: [RFC v3 03/25] hw/iommu: introduce IOMMUContext

[David Gibson <david@gibson.dropbear.id.au>]

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On Wed, Jan 29, 2020 at 04:16:34AM -0800, Liu, Yi L wrote:
> From: Peter Xu <peterx@redhat.com>
> 
> Currently, many platform vendors provide the capability of dual stage
> DMA address translation in hardware. For example, nested translation
> on Intel VT-d scalable mode, nested stage translation on ARM SMMUv3,
> and etc. Also there are efforts to make QEMU vIOMMU be backed by dual
> stage DMA address translation capability provided by hardware to have
> better address translation support for passthru devices.
> 
> As so, making vIOMMU be backed by dual stage translation capability
> requires QEMU vIOMMU to have a way to get aware of such hardware
> capability and also require a way to receive DMA address translation
> faults (e.g. I/O page request) from host as guest owns stage-1 translation
> structures in dual stage DAM address translation.
> 
> This patch adds IOMMUContext as an abstract of vIOMMU related operations.
> Like provide a way for passthru modules (e.g. VFIO) to register
> DualStageIOMMUObject instances. And in future, it is expected to offer
> support for receiving host DMA translation faults happened on stage-1
> translation.
> 
> For more backgrounds, may refer to the discussion below, while there
> is also difference between the current implementation and original
> proposal. This patch introduces the IOMMUContext as an abstract layer
> for passthru module (e.g. VFIO) calls into vIOMMU. The first introduced
> interface is to make QEMU vIOMMU be aware of dual stage translation
> capability.
> 
> https://lists.gnu.org/archive/html/qemu-devel/2019-07/msg05022.html

Again, is there a reason for not making this a QOM class or interface?


I'm not very clear on the relationship betwen an IOMMUContext and a
DualStageIOMMUObject.  Can there be many IOMMUContexts to a
DualStageIOMMUOBject?  The other way around?  Or is it just
zero-or-one DualStageIOMMUObjects to an IOMMUContext?

> Cc: Kevin Tian <kevin.tian@intel.com>
> Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
> Cc: Peter Xu <peterx@redhat.com>
> Cc: Eric Auger <eric.auger@redhat.com>
> Cc: Yi Sun <yi.y.sun@linux.intel.com>
> Cc: David Gibson <david@gibson.dropbear.id.au>
> Signed-off-by: Peter Xu <peterx@redhat.com>
> Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
> ---
>  hw/iommu/Makefile.objs           |  1 +
>  hw/iommu/iommu_context.c         | 54 +++++++++++++++++++++++++++++++++++
>  include/hw/iommu/iommu_context.h | 61 ++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 116 insertions(+)
>  create mode 100644 hw/iommu/iommu_context.c
>  create mode 100644 include/hw/iommu/iommu_context.h
> 
> diff --git a/hw/iommu/Makefile.objs b/hw/iommu/Makefile.objs
> index d4f3b39..1e45072 100644
> --- a/hw/iommu/Makefile.objs
> +++ b/hw/iommu/Makefile.objs
> @@ -1 +1,2 @@
>  obj-y += dual_stage_iommu.o
> +obj-y += iommu_context.o
> diff --git a/hw/iommu/iommu_context.c b/hw/iommu/iommu_context.c
> new file mode 100644
> index 0000000..6340ca3
> --- /dev/null
> +++ b/hw/iommu/iommu_context.c
> @@ -0,0 +1,54 @@
> +/*
> + * QEMU abstract of vIOMMU context
> + *
> + * Copyright (C) 2020 Red Hat Inc.
> + *
> + * Authors: Peter Xu <peterx@redhat.com>,
> + *          Liu Yi L <yi.l.liu@intel.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> +
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> +
> + * You should have received a copy of the GNU General Public License along
> + * with this program; if not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#include "qemu/osdep.h"
> +#include "hw/iommu/iommu_context.h"
> +
> +int iommu_context_register_ds_iommu(IOMMUContext *iommu_ctx,
> +                                    DualStageIOMMUObject *dsi_obj)
> +{
> +    if (!iommu_ctx || !dsi_obj) {

Would this ever happen apart from a bug in the caller?  If not it
should be an assert().

> +        return -ENOENT;
> +    }
> +
> +    if (iommu_ctx->ops && iommu_ctx->ops->register_ds_iommu) {
> +        return iommu_ctx->ops->register_ds_iommu(iommu_ctx, dsi_obj);
> +    }
> +    return -ENOENT;
> +}
> +
> +void iommu_context_unregister_ds_iommu(IOMMUContext *iommu_ctx,
> +                                      DualStageIOMMUObject *dsi_obj)
> +{
> +    if (!iommu_ctx || !dsi_obj) {
> +        return;
> +    }
> +
> +    if (iommu_ctx->ops && iommu_ctx->ops->unregister_ds_iommu) {
> +        iommu_ctx->ops->unregister_ds_iommu(iommu_ctx, dsi_obj);
> +    }
> +}
> +
> +void iommu_context_init(IOMMUContext *iommu_ctx, IOMMUContextOps *ops)
> +{
> +    iommu_ctx->ops = ops;
> +}
> diff --git a/include/hw/iommu/iommu_context.h b/include/hw/iommu/iommu_context.h
> new file mode 100644
> index 0000000..6f2ccb5
> --- /dev/null
> +++ b/include/hw/iommu/iommu_context.h
> @@ -0,0 +1,61 @@
> +/*
> + * QEMU abstraction of IOMMU Context
> + *
> + * Copyright (C) 2020 Red Hat Inc.
> + *
> + * Authors: Peter Xu <peterx@redhat.com>,
> + *          Liu, Yi L <yi.l.liu@intel.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> +
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> +
> + * You should have received a copy of the GNU General Public License along
> + * with this program; if not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#ifndef HW_IOMMU_CONTEXT_H
> +#define HW_IOMMU_CONTEXT_H
> +
> +#include "qemu/queue.h"
> +#ifndef CONFIG_USER_ONLY
> +#include "exec/hwaddr.h"
> +#endif
> +#include "hw/iommu/dual_stage_iommu.h"
> +
> +typedef struct IOMMUContext IOMMUContext;
> +typedef struct IOMMUContextOps IOMMUContextOps;
> +
> +struct IOMMUContextOps {
> +    /*
> +     * Register DualStageIOMMUObject to vIOMMU thus vIOMMU
> +     * is aware of dual stage translation capability, and
> +     * also be able to setup dual stage translation via
> +     * interfaces exposed by DualStageIOMMUObject.
> +     */
> +    int (*register_ds_iommu)(IOMMUContext *iommu_ctx,
> +                             DualStageIOMMUObject *dsi_obj);
> +    void (*unregister_ds_iommu)(IOMMUContext *iommu_ctx,
> +                                DualStageIOMMUObject *dsi_obj);
> +};
> +
> +/*
> + * This is an abstraction of IOMMU context.
> + */
> +struct IOMMUContext {
> +    IOMMUContextOps *ops;
> +};
> +
> +int iommu_context_register_ds_iommu(IOMMUContext *iommu_ctx,
> +                                    DualStageIOMMUObject *dsi_obj);
> +void iommu_context_unregister_ds_iommu(IOMMUContext *iommu_ctx,
> +                                       DualStageIOMMUObject *dsi_obj);
> +void iommu_context_init(IOMMUContext *iommu_ctx, IOMMUContextOps *ops);
> +
> +#endif

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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