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Re: [PATCH v2 1/3] vfio: Find DMA available capability
From: |
Philippe Mathieu-Daudé |
Subject: |
Re: [PATCH v2 1/3] vfio: Find DMA available capability |
Date: |
Tue, 15 Sep 2020 08:14:24 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 |
Hi Matthew,
On 9/15/20 12:29 AM, Matthew Rosato wrote:
> The underlying host may be limiting the number of outstanding DMA
> requests for type 1 IOMMU. Add helper functions to check for the
> DMA available capability and retrieve the current number of DMA
> mappings allowed.
>
> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
> ---
> hw/vfio/common.c | 37 +++++++++++++++++++++++++++++++++++++
> include/hw/vfio/vfio-common.h | 2 ++
> 2 files changed, 39 insertions(+)
>
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index 3335714..7f4a338 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -844,6 +844,43 @@ vfio_get_region_info_cap(struct vfio_region_info *info,
> uint16_t id)
> return NULL;
> }
>
> +static struct vfio_info_cap_header *
> +vfio_get_iommu_type1_info_cap(struct vfio_iommu_type1_info *info, uint16_t
> id)
> +{
> + struct vfio_info_cap_header *hdr;
> + void *ptr = info;
> +
> + if (!(info->flags & VFIO_IOMMU_INFO_CAPS)) {
> + return NULL;
> + }
> +
> + for (hdr = ptr + info->cap_offset; hdr != ptr; hdr = ptr + hdr->next) {
> + if (hdr->id == id) {
> + return hdr;
> + }
> + }
> +
> + return NULL;
> +}
> +
> +bool vfio_get_info_dma_avail(struct vfio_iommu_type1_info *info,
> + unsigned int *avail)
> +{
> + struct vfio_info_cap_header *hdr;
> + struct vfio_iommu_type1_info_dma_avail *cap;
> +
> + /* If the capability cannot be found, assume no DMA limiting */
> + hdr = vfio_get_iommu_type1_info_cap(info,
> + VFIO_IOMMU_TYPE1_INFO_DMA_AVAIL);
> + if (hdr == NULL || avail == NULL) {
If you expect the caller to use avail=NULL, then why
return false when there is available information?
> + return false;
> + }
> +
> + cap = (void *) hdr;
> + *avail = cap->avail;
> + return true;
> +}
> +
> static int vfio_setup_region_sparse_mmaps(VFIORegion *region,
> struct vfio_region_info *info)
> {
> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
> index c78f3ff..661a380 100644
> --- a/include/hw/vfio/vfio-common.h
> +++ b/include/hw/vfio/vfio-common.h
> @@ -178,6 +178,8 @@ VFIOGroup *vfio_get_group(int groupid, AddressSpace *as,
> Error **errp);
> void vfio_put_group(VFIOGroup *group);
> int vfio_get_device(VFIOGroup *group, const char *name,
> VFIODevice *vbasedev, Error **errp);
> +bool vfio_get_info_dma_avail(struct vfio_iommu_type1_info *info,
> + unsigned int *avail);
>
> extern const MemoryRegionOps vfio_region_ops;
> typedef QLIST_HEAD(VFIOGroupList, VFIOGroup) VFIOGroupList;
>