Messages in this thread | | | Date | Mon, 8 Aug 2022 01:55:45 +0530 | Subject | Re: [Freedreno] [PATCH 1/3] dma-buf: Add ioctl to query mmap info | From | Akhil P Oommen <> |
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On 7/29/2022 10:37 PM, Rob Clark wrote: > From: Rob Clark <robdclark@chromium.org> > > This is a fairly narrowly focused interface, providing a way for a VMM > in userspace to tell the guest kernel what pgprot settings to use when > mapping a buffer to guest userspace. > > For buffers that get mapped into guest userspace, virglrenderer returns > a dma-buf fd to the VMM (crosvm or qemu). In addition to mapping the > pages into the guest VM, it needs to report to drm/virtio in the guest > the cache settings to use for guest userspace. In particular, on some > architectures, creating aliased mappings with different cache attributes > is frowned upon, so it is important that the guest mappings have the > same cache attributes as any potential host mappings. > > Signed-off-by: Rob Clark <robdclark@chromium.org> > --- > drivers/dma-buf/dma-buf.c | 26 ++++++++++++++++++++++++++ > include/linux/dma-buf.h | 7 +++++++ > include/uapi/linux/dma-buf.h | 28 ++++++++++++++++++++++++++++ > 3 files changed, 61 insertions(+) > > diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c > index 32f55640890c..d02d6c2a3b49 100644 > --- a/drivers/dma-buf/dma-buf.c > +++ b/drivers/dma-buf/dma-buf.c > @@ -326,6 +326,29 @@ static long dma_buf_set_name(struct dma_buf *dmabuf, const char __user *buf) > return 0; > } > > +static long dma_buf_info(struct dma_buf *dmabuf, const void __user *uarg) > +{ > + struct dma_buf_info arg; > + > + if (copy_from_user(&arg, uarg, sizeof(arg))) > + return -EFAULT; > + > + switch (arg.param) { > + case DMA_BUF_INFO_VM_PROT: > + if (!dmabuf->ops->mmap_info) > + return -ENOSYS; > + arg.value = dmabuf->ops->mmap_info(dmabuf); > + break; > + default: > + return -EINVAL; > + } > + > + if (copy_to_user(uarg, &arg, sizeof(arg))) > + return -EFAULT; > + > + return 0; > +} > + > static long dma_buf_ioctl(struct file *file, > unsigned int cmd, unsigned long arg) > { > @@ -369,6 +392,9 @@ static long dma_buf_ioctl(struct file *file, > case DMA_BUF_SET_NAME_B: > return dma_buf_set_name(dmabuf, (const char __user *)arg); > > + case DMA_BUF_IOCTL_INFO: > + return dma_buf_info(dmabuf, (const void __user *)arg); > + > default: > return -ENOTTY; > } > diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h > index 71731796c8c3..6f4de64a5937 100644 > --- a/include/linux/dma-buf.h > +++ b/include/linux/dma-buf.h > @@ -283,6 +283,13 @@ struct dma_buf_ops { > */ > int (*mmap)(struct dma_buf *, struct vm_area_struct *vma); > > + /** > + * @mmap_info: > + * > + * Return mmapping info for the buffer. See DMA_BUF_INFO_VM_PROT. > + */ > + int (*mmap_info)(struct dma_buf *); > + > int (*vmap)(struct dma_buf *dmabuf, struct iosys_map *map); > void (*vunmap)(struct dma_buf *dmabuf, struct iosys_map *map); > }; > diff --git a/include/uapi/linux/dma-buf.h b/include/uapi/linux/dma-buf.h > index b1523cb8ab30..a41adac0f46a 100644 > --- a/include/uapi/linux/dma-buf.h > +++ b/include/uapi/linux/dma-buf.h > @@ -85,6 +85,32 @@ struct dma_buf_sync { > > #define DMA_BUF_NAME_LEN 32 > > + > +/** > + * struct dma_buf_info - Query info about the buffer. > + */ > +struct dma_buf_info { > + > +#define DMA_BUF_INFO_VM_PROT 1 > +# define DMA_BUF_VM_PROT_WC 0 > +# define DMA_BUF_VM_PROT_CACHED 1 > + > + /** > + * @param: Which param to query > + * > + * DMA_BUF_INFO_BM_PROT: Is there a typo here? BM -> VM ?
-Akhil. > + * Query the access permissions of userspace mmap's of this buffer. > + * Returns one of DMA_BUF_VM_PROT_x > + */ > + __u32 param; > + __u32 pad; > + > + /** > + * @value: Return value of the query. > + */ > + __u64 value; > +}; > + > #define DMA_BUF_BASE 'b' > #define DMA_BUF_IOCTL_SYNC _IOW(DMA_BUF_BASE, 0, struct dma_buf_sync) > > @@ -95,4 +121,6 @@ struct dma_buf_sync { > #define DMA_BUF_SET_NAME_A _IOW(DMA_BUF_BASE, 1, __u32) > #define DMA_BUF_SET_NAME_B _IOW(DMA_BUF_BASE, 1, __u64) > > +#define DMA_BUF_IOCTL_INFO _IOWR(DMA_BUF_BASE, 2, struct dma_buf_info) > + > #endif
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