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SubjectRe: [PATCH v9 3/7] vfio/type1: bypass unmap/unpin and replay for VFIO_IOVA_RESERVED slots
On Wed,  4 May 2016 11:54:14 +0000
Eric Auger <eric.auger@linaro.org> wrote:

> Before allowing the end-user to create VFIO_IOVA_RESERVED dma slots,
> let's implement the expected behavior for removal and replay. As opposed
> to user dma slots, IOVAs are not systematically bound to PAs and PAs are
> not pinned. VFIO just initializes the IOVA "aperture". IOVAs are allocated
> outside of the VFIO framework, typically the MSI layer which is
> responsible to free and unmap them. The MSI mapping resources are freeed
> by the IOMMU driver on domain destruction.
>
> Signed-off-by: Eric Auger <eric.auger@linaro.org>
>
> ---
>
> v7 -> v8:
> - do no destroy anything anymore, just bypass unmap/unpin and iommu_map
> on replay
> ---
> drivers/vfio/vfio_iommu_type1.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 2d769d4..94a9916 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -391,7 +391,7 @@ static void vfio_unmap_unpin(struct vfio_iommu *iommu, struct vfio_dma *dma)
> struct vfio_domain *domain, *d;
> long unlocked = 0;
>
> - if (!dma->size)
> + if (!dma->size || dma->type != VFIO_IOVA_USER)
> return;
> /*
> * We use the IOMMU to track the physical addresses, otherwise we'd
> @@ -727,6 +727,9 @@ static int vfio_iommu_replay(struct vfio_iommu *iommu,
> dma = rb_entry(n, struct vfio_dma, node);
> iova = dma->iova;
>
> + if (dma->type == VFIO_IOVA_RESERVED)
> + continue;
> +

But you do still need some sort of replay mechanism, right? Not to
replay the IOVA to PA mapping, but to call iommu_msi_set_aperture() for
the new domain. How will you know that this entry is an MSI reserved
range or something else? Perhaps we can't have a generic "reserved"
type here.

> while (iova < dma->iova + dma->size) {
> phys_addr_t phys = iommu_iova_to_phys(d->domain, iova);
> size_t size;

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