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Re: [Qemu-devel] [RFC v2 1/4] Add EXEC_FLAG to VFIO DMA mappings
From: |
Eric Auger |
Subject: |
Re: [Qemu-devel] [RFC v2 1/4] Add EXEC_FLAG to VFIO DMA mappings |
Date: |
Fri, 23 May 2014 10:40:29 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 |
On 05/11/2014 07:13 PM, Alvise Rigo wrote:
> The flag is mandatory for the ARM SMMU so we always add it if the MMIO
> handles it.
Hi Alvise,
Refering to the root problem explanation found in
https://lkml.org/lkml/2014/2/8/176, I understand the problem is specific
to devices that fetch instructions from executable memory region
sections (XN =0).
Typically this is not the case of Midway xgmac which does not need
executable regions and hence does not need that change.
in
http://lists.linuxfoundation.org/pipermail/iommu/2013-November/007095.html,
Will says most IOMMU mappings should be XN.
I am not knowledged enough on mem mapping settings to understand the
consequences of always setting XN=0, even for devices that do not need
request it.
Does anyone have an opinion on this?
Best Regards
Eric
>
> Signed-off-by: Alvise Rigo <address@hidden>
> ---
> hw/vfio/common.c | 9 +++++++++
> hw/vfio/vfio-common.h | 1 +
> linux-headers/linux/vfio.h | 2 ++
> 3 files changed, 12 insertions(+)
>
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index 9d1f723..a805c5d 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -107,6 +107,11 @@ static int vfio_dma_map(VFIOContainer *container, hwaddr
> iova,
> map.flags |= VFIO_DMA_MAP_FLAG_WRITE;
> }
>
> + /* add exec flag */
> + if (container->iommu_data.has_exec_cap) {
> + map.flags |= VFIO_DMA_MAP_FLAG_EXEC;
> + }
> +
> /*
> * Try the mapping, if it fails with EBUSY, unmap the region and try
> * again. This shouldn't be necessary, but we sometimes see it in
> @@ -352,6 +357,10 @@ static int vfio_connect_container(VFIOGroup *group)
> return -errno;
> }
>
> + if (ioctl(fd, VFIO_CHECK_EXTENSION, VFIO_IOMMU_PROT_EXEC)) {
> + container->iommu_data.has_exec_cap = true;
> + }
> +
> container->iommu_data.type1.listener = vfio_memory_listener;
> container->iommu_data.release = vfio_listener_release;
>
> diff --git a/hw/vfio/vfio-common.h b/hw/vfio/vfio-common.h
> index 21148ef..1abbd1a 100644
> --- a/hw/vfio/vfio-common.h
> +++ b/hw/vfio/vfio-common.h
> @@ -35,6 +35,7 @@ typedef struct VFIOContainer {
> union {
> VFIOType1 type1;
> };
> + bool has_exec_cap; /* support of exec capability by the IOMMU */
> void (*release)(struct VFIOContainer *);
> } iommu_data;
> QLIST_HEAD(, VFIOGroup) group_list;
> diff --git a/linux-headers/linux/vfio.h b/linux-headers/linux/vfio.h
> index 17c58e0..95a02c5 100644
> --- a/linux-headers/linux/vfio.h
> +++ b/linux-headers/linux/vfio.h
> @@ -24,6 +24,7 @@
> #define VFIO_TYPE1_IOMMU 1
> #define VFIO_SPAPR_TCE_IOMMU 2
>
> +#define VFIO_IOMMU_PROT_EXEC 5
> /*
> * The IOCTL interface is designed for extensibility by embedding the
> * structure length (argsz) and flags into structures passed between
> @@ -392,6 +393,7 @@ struct vfio_iommu_type1_dma_map {
> __u32 flags;
> #define VFIO_DMA_MAP_FLAG_READ (1 << 0) /* readable from device
> */
> #define VFIO_DMA_MAP_FLAG_WRITE (1 << 1) /* writable from device */
> +#define VFIO_DMA_MAP_FLAG_EXEC (1 << 2) /* executable from device */
> __u64 vaddr; /* Process virtual address */
> __u64 iova; /* IO virtual address */
> __u64 size; /* Size of mapping (bytes) */
>