Re: [Xen-devel] [PATCH 6/7] x86: add iommu_op to query reserved ranges

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Paul Durrant
> Sent: Monday, February 12, 2018 6:47 PM
> 
> Certain areas of memory, such as RMRRs, must be mapped 1:1
> (i.e. BFN == MFN) through the IOMMU.
> 
> This patch adds an iommu_op to allow these ranges to be queried.
> 
> Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
> ---
> Cc: Jan Beulich <jbeulich@xxxxxxxx>
> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Cc: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
> Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> Cc: Tim Deegan <tim@xxxxxxx>
> Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
> ---
>  xen/arch/x86/iommu_op.c       | 121
> ++++++++++++++++++++++++++++++++++++++++++
>  xen/include/public/iommu_op.h |  35 ++++++++++++
>  xen/include/xlat.lst          |   2 +
>  3 files changed, 158 insertions(+)
> 
> diff --git a/xen/arch/x86/iommu_op.c b/xen/arch/x86/iommu_op.c
> index edd8a384b3..ac81b98b7a 100644
> --- a/xen/arch/x86/iommu_op.c
> +++ b/xen/arch/x86/iommu_op.c
> @@ -22,6 +22,58 @@
>  #include <xen/event.h>
>  #include <xen/guest_access.h>
>  #include <xen/hypercall.h>
> +#include <xen/iommu.h>
> +
> +struct get_rdm_ctxt {
> +    unsigned int max_entries;
> +    unsigned int nr_entries;
> +    XEN_GUEST_HANDLE(xen_iommu_reserved_region_t) regions;
> +};
> +
> +static int get_rdm(xen_pfn_t start, xen_ulong_t nr, u32 id, void *arg)
> +{
> +    struct get_rdm_ctxt *ctxt = arg;
> +
> +    if ( ctxt->nr_entries < ctxt->max_entries )
> +    {
> +        xen_iommu_reserved_region_t region = {
> +            .start_bfn = start,
> +            .nr_frames = nr,
> +        };
> +
> +        if ( copy_to_guest_offset(ctxt->regions, ctxt->nr_entries, &region,
> +                                  1) )
> +            return -EFAULT;

RMRR entries are device specific. it's why a 'id' (i.e. sbdf) field 
is introduced for such check.

> +    }
> +
> +    ctxt->nr_entries++;
> +
> +    return 1;
> +}
> +
> +static int iommuop_query_reserved(struct
> xen_iommu_op_query_reserved *op)

I didn't get why we cannot reuse existing XENMEM_reserved_
device_memory_map?

Thanks
Kevin
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