diff mbox series

[2/5] udmabuf: allow userspace to set map attributes

Message ID 20191126011056.67928-2-gurchetansingh@chromium.org (mailing list archive)
State New, archived
Headers show
Series [1/5] udmabuf: use cache_sgt_mapping option | expand

Commit Message

Gurchetan Singh Nov. 26, 2019, 1:10 a.m. UTC 
The main use for udmabuf is sending guest memory pages
to the host.

It's generally a bad idea to have to separate mappings with
different attributes. For example, a WC mapping the guest
kernel and cached mapping on the host is problematic.

v2: Cache attribute flags instead of read/write flags (kraxel@)
---
 drivers/dma-buf/udmabuf.c    | 12 ++++++++++++
 include/uapi/linux/udmabuf.h |  2 ++
 2 files changed, 14 insertions(+)

Comments

Gerd Hoffmann Nov. 28, 2019, 11:48 a.m. UTC | #1 
Hi,

> diff --git a/include/uapi/linux/udmabuf.h b/include/uapi/linux/udmabuf.h
> index 46b6532ed855..f90831f2bb0d 100644
> --- a/include/uapi/linux/udmabuf.h
> +++ b/include/uapi/linux/udmabuf.h
> @@ -6,6 +6,8 @@
>  #include <linux/ioctl.h>
>  
>  #define UDMABUF_FLAGS_CLOEXEC	0x01
> +#define UDMABUF_FLAGS_WC	0x02
> +#define UDMABUF_FLAGS_NONCACHED 0x04
>  
>  struct udmabuf_create {
>  	__u32 memfd;

This is a uapi change and should go to a separate patch,
clearly flagging that in $subject.

(new policy by airlied for the drm tree).

Otherwise the series looks good to me.

cheers,
  Gerd
Gurchetan Singh Dec. 3, 2019, 1:48 a.m. UTC | #2 
On Thu, Nov 28, 2019 at 3:48 AM Gerd Hoffmann <kraxel@redhat.com> wrote:
>
>   Hi,
>
> > diff --git a/include/uapi/linux/udmabuf.h b/include/uapi/linux/udmabuf.h
> > index 46b6532ed855..f90831f2bb0d 100644
> > --- a/include/uapi/linux/udmabuf.h
> > +++ b/include/uapi/linux/udmabuf.h
> > @@ -6,6 +6,8 @@
> >  #include <linux/ioctl.h>
> >
> >  #define UDMABUF_FLAGS_CLOEXEC        0x01
> > +#define UDMABUF_FLAGS_WC     0x02
> > +#define UDMABUF_FLAGS_NONCACHED 0x04
> >
> >  struct udmabuf_create {
> >       __u32 memfd;
>
> This is a uapi change and should go to a separate patch,
> clearly flagging that in $subject.
>
> (new policy by airlied for the drm tree).

The new policy requires a non-toy userspace[1], which may take a
while.  Removed the UAPI changes in the latest patch series.

[1] https://01.org/linuxgraphics/gfx-docs/drm/gpu/drm-uapi.html#open-source-userspace-requirements

>
> Otherwise the series looks good to me.
>
> cheers,
>   Gerd
>
diff mbox series

Patch

diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
index b345e91d831a..ce9caaaa9e4b 100644
--- a/drivers/dma-buf/udmabuf.c
+++ b/drivers/dma-buf/udmabuf.c
@@ -16,6 +16,7 @@  static const u32    list_limit = 1024;  /* udmabuf_create_list->count limit */
 static const size_t size_limit_mb = 64; /* total dmabuf size, in megabytes  */
 
 struct udmabuf {
+	u32 flags;
 	pgoff_t pagecount;
 	struct page **pages;
 };
@@ -37,6 +38,12 @@  static const struct vm_operations_struct udmabuf_vm_ops = {
 static int mmap_udmabuf(struct dma_buf *buf, struct vm_area_struct *vma)
 {
 	struct udmabuf *ubuf = buf->priv;
+	pgprot_t pgprot = vm_get_page_prot(vma->vm_flags);
+
+	if (ubuf->flags & UDMABUF_FLAGS_WC)
+		vma->vm_page_prot = pgprot_writecombine(pgprot);
+	else if (ubuf->flags & UDMABUF_FLAGS_NONCACHED)
+		vma->vm_page_prot = pgprot_noncached(pgprot);
 
 	if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) == 0)
 		return -EINVAL;
@@ -132,6 +139,10 @@  static long udmabuf_create(const struct udmabuf_create_list *head,
 	int seals, ret = -EINVAL;
 	u32 i, flags;
 
+	if ((head->flags & UDMABUF_FLAGS_NONCACHED) &&
+	    (head->flags & UDMABUF_FLAGS_WC))
+		return -EINVAL;
+
 	ubuf = kzalloc(sizeof(*ubuf), GFP_KERNEL);
 	if (!ubuf)
 		return -ENOMEM;
@@ -188,6 +199,7 @@  static long udmabuf_create(const struct udmabuf_create_list *head,
 	exp_info.priv = ubuf;
 	exp_info.flags = O_RDWR;
 
+	ubuf->flags = head->flags;
 	buf = dma_buf_export(&exp_info);
 	if (IS_ERR(buf)) {
 		ret = PTR_ERR(buf);
diff --git a/include/uapi/linux/udmabuf.h b/include/uapi/linux/udmabuf.h
index 46b6532ed855..f90831f2bb0d 100644
--- a/include/uapi/linux/udmabuf.h
+++ b/include/uapi/linux/udmabuf.h
@@ -6,6 +6,8 @@ 
 #include <linux/ioctl.h>
 
 #define UDMABUF_FLAGS_CLOEXEC	0x01
+#define UDMABUF_FLAGS_WC	0x02
+#define UDMABUF_FLAGS_NONCACHED 0x04
 
 struct udmabuf_create {
 	__u32 memfd;