[PATCH] Add grant references for fbfront/kbdfront

[PATCH] Add grant references for fbfront/kbdfront

[Konrad Rzeszutek Wilk]

This patchset is proposed for 2.6.39.

The patchset description from:
http://lists.colo.xensource.com/archives/html/xen-devel/2011-03/msg00381.html

This series fixes the interface for the fbfront and kbdfront devices,
which were storing MFNs in xenstore rather than creating grant table
entries. To maintain backwards compatibility, a different xenstore key
is used (page-gref instead of page-ref) and the use of grants must be
requested for fbfront (because two levels of page references are
embedded within the shared page). This makes it possible to move a
display server out of dom0 without giving the display domain full access
to other domain's memory.

Changes since v1:
        Updated xenstore key to "feature-grants"

Updated frontend patch has been sent to qemu-devel.


 drivers/input/xen-kbdfront.c |   39 +++++++++----
 drivers/video/xen-fbfront.c  |  126 ++++++++++++++++++++++++++++++++++-------
 2 files changed, 132 insertions(+), 33 deletions(-)

Daniel De Graaf (3):
      xen-fbfront: Read width/height from backend
      xen-kbdfront: Add grant reference for shared page
      xen-fbfront: Use grant references when requested

[PATCH 1/4] xen-fbfront: Read width/height from backend

[Konrad Rzeszutek Wilk]

From: Daniel De Graaf <dgdegra@tycho.nsa.gov>

This allows the backend driver to specify the size of the framebuffer
instead of requiring it to be on the kernel command line.

Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Ian Campbell <Ian.Campbell@eu.citrix.com>
---
 drivers/video/xen-fbfront.c |   30 ++++++++++++++++++++++++------
 1 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/drivers/video/xen-fbfront.c b/drivers/video/xen-fbfront.c
index a20218c..56d6061 100644
--- a/drivers/video/xen-fbfront.c
+++ b/drivers/video/xen-fbfront.c
@@ -58,7 +58,7 @@ struct xenfb_info {
 #define XENFB_DEFAULT_FB_LEN (XENFB_WIDTH * XENFB_HEIGHT * XENFB_DEPTH / 8)
 
 enum { KPARAM_MEM, KPARAM_WIDTH, KPARAM_HEIGHT, KPARAM_CNT };
-static int video[KPARAM_CNT] = { 2, XENFB_WIDTH, XENFB_HEIGHT };
+static int video[KPARAM_CNT] = { 0, 0, 0 };
 module_param_array(video, int, NULL, 0);
 MODULE_PARM_DESC(video,
 	"Video memory size in MB, width, height in pixels (default 2,800,600)");
@@ -363,7 +363,7 @@ static int __devinit xenfb_probe(struct xenbus_device *dev,
 {
 	struct xenfb_info *info;
 	struct fb_info *fb_info;
-	int fb_size;
+	int fb_size, fb_need;
 	int val;
 	int ret;
 
@@ -375,14 +375,32 @@ static int __devinit xenfb_probe(struct xenbus_device *dev,
 
 	/* Limit kernel param videoram amount to what is in xenstore */
 	if (xenbus_scanf(XBT_NIL, dev->otherend, "videoram", "%d", &val) == 1) {
-		if (val < video[KPARAM_MEM])
+		if (!video[KPARAM_MEM] || val < video[KPARAM_MEM])
 			video[KPARAM_MEM] = val;
 	}
 
+	/* Take width/height from xenstore if not set on command line */
+	if (!video[KPARAM_WIDTH]) {
+		if (xenbus_scanf(XBT_NIL, dev->otherend, "width", "%d", &val) == 1)
+			video[KPARAM_WIDTH] = val;
+		else
+			video[KPARAM_WIDTH] = XENFB_WIDTH;
+	}
+	if (!video[KPARAM_HEIGHT]) {
+		if (xenbus_scanf(XBT_NIL, dev->otherend, "height", "%d", &val) == 1)
+			video[KPARAM_HEIGHT] = val;
+		else
+			video[KPARAM_HEIGHT] = XENFB_HEIGHT;
+	}
+
+	fb_need = video[KPARAM_WIDTH] * video[KPARAM_HEIGHT] * XENFB_DEPTH / 8;
+	if (video[KPARAM_MEM])
+		fb_size = video[KPARAM_MEM] * 1024 * 1024;
+	else
+		fb_size = video[KPARAM_MEM] = fb_need;
+
 	/* If requested res does not fit in available memory, use default */
-	fb_size = video[KPARAM_MEM] * 1024 * 1024;
-	if (video[KPARAM_WIDTH] * video[KPARAM_HEIGHT] * XENFB_DEPTH / 8
-	    > fb_size) {
+	if (fb_need > fb_size) {
 		video[KPARAM_WIDTH] = XENFB_WIDTH;
 		video[KPARAM_HEIGHT] = XENFB_HEIGHT;
 		fb_size = XENFB_DEFAULT_FB_LEN;
-- 
1.7.1

[PATCH 2/4] xen-kbdfront: Add grant reference for shared page

[Konrad Rzeszutek Wilk]

From: Daniel De Graaf <dgdegra@tycho.nsa.gov>

Without a grant reference, full access to the domain's memory is
required to use the shared page. Add an additional parameter in
xenstore to allow grant mapping to be used.

Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Ian Campbell <Ian.Campbell@eu.citrix.com>
---
 drivers/input/xen-kbdfront.c |   39 ++++++++++++++++++++++++++++-----------
 1 files changed, 28 insertions(+), 11 deletions(-)

diff --git a/drivers/input/xen-kbdfront.c b/drivers/input/xen-kbdfront.c
index 7f85a86..a5c064e 100644
--- a/drivers/input/xen-kbdfront.c
+++ b/drivers/input/xen-kbdfront.c
@@ -11,12 +11,6 @@
  *  more details.
  */
 
-/*
- * TODO:
- *
- * Switch to grant tables together with xen-fbfront.c.
- */
-
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
 #include <linux/kernel.h>
@@ -30,6 +24,8 @@
 #include <xen/xen.h>
 #include <xen/events.h>
 #include <xen/page.h>
+#include <xen/grant_table.h>
+#include <xen/interface/grant_table.h>
 #include <xen/interface/io/fbif.h>
 #include <xen/interface/io/kbdif.h>
 #include <xen/xenbus.h>
@@ -38,6 +34,7 @@ struct xenkbd_info {
 	struct input_dev *kbd;
 	struct input_dev *ptr;
 	struct xenkbd_page *page;
+	int gref;
 	int irq;
 	struct xenbus_device *xbdev;
 	char phys[32];
@@ -122,6 +119,7 @@ static int __devinit xenkbd_probe(struct xenbus_device *dev,
 	dev_set_drvdata(&dev->dev, info);
 	info->xbdev = dev;
 	info->irq = -1;
+	info->gref = -1;
 	snprintf(info->phys, sizeof(info->phys), "xenbus/%s", dev->nodename);
 
 	info->page = (void *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
@@ -218,15 +216,20 @@ static int xenkbd_connect_backend(struct xenbus_device *dev,
 	int ret, evtchn;
 	struct xenbus_transaction xbt;
 
+	ret = gnttab_grant_foreign_access(dev->otherend_id,
+	                                  virt_to_mfn(info->page), 0);
+	if (ret < 0)
+		return ret;
+	info->gref = ret;
+
 	ret = xenbus_alloc_evtchn(dev, &evtchn);
 	if (ret)
-		return ret;
+		goto error_grant;
 	ret = bind_evtchn_to_irqhandler(evtchn, input_handler,
 					0, dev->devicetype, info);
 	if (ret < 0) {
-		xenbus_free_evtchn(dev, evtchn);
 		xenbus_dev_fatal(dev, ret, "bind_evtchn_to_irqhandler");
-		return ret;
+		goto error_evtchan;
 	}
 	info->irq = ret;
 
@@ -234,12 +237,15 @@ static int xenkbd_connect_backend(struct xenbus_device *dev,
 	ret = xenbus_transaction_start(&xbt);
 	if (ret) {
 		xenbus_dev_fatal(dev, ret, "starting transaction");
-		return ret;
+		goto error_irqh;
 	}
 	ret = xenbus_printf(xbt, dev->nodename, "page-ref", "%lu",
 			    virt_to_mfn(info->page));
 	if (ret)
 		goto error_xenbus;
+	ret = xenbus_printf(xbt, dev->nodename, "page-gref", "%u", info->gref);
+	if (ret)
+		goto error_xenbus;
 	ret = xenbus_printf(xbt, dev->nodename, "event-channel", "%u",
 			    evtchn);
 	if (ret)
@@ -249,7 +255,7 @@ static int xenkbd_connect_backend(struct xenbus_device *dev,
 		if (ret == -EAGAIN)
 			goto again;
 		xenbus_dev_fatal(dev, ret, "completing transaction");
-		return ret;
+		goto error_irqh;
 	}
 
 	xenbus_switch_state(dev, XenbusStateInitialised);
@@ -258,6 +264,14 @@ static int xenkbd_connect_backend(struct xenbus_device *dev,
  error_xenbus:
 	xenbus_transaction_end(xbt, 1);
 	xenbus_dev_fatal(dev, ret, "writing xenstore");
+ error_irqh:
+	unbind_from_irqhandler(info->irq, info);
+	info->irq = -1;
+ error_evtchan:
+	xenbus_free_evtchn(dev, evtchn);
+ error_grant:
+	gnttab_end_foreign_access_ref(info->gref, 0);
+	info->gref = -1;
 	return ret;
 }
 
@@ -266,6 +280,9 @@ static void xenkbd_disconnect_backend(struct xenkbd_info *info)
 	if (info->irq >= 0)
 		unbind_from_irqhandler(info->irq, info);
 	info->irq = -1;
+	if (info->gref >= 0)
+		gnttab_end_foreign_access_ref(info->gref, 0);
+	info->gref = -1;
 }
 
 static void xenkbd_backend_changed(struct xenbus_device *dev,
-- 
1.7.1

[PATCH 3/4] xen-fbfront: Use grant references when requested

[Konrad Rzeszutek Wilk]

From: Daniel De Graaf <dgdegra@tycho.nsa.gov>

The current version of the Xen framebuffer API passes MFNs directly
to the backend driver, which requires the backend to have full access
to this domain's memory. Add a parameter in xenbus to request the use of
grant entries instead, which are slightly slower to map but provide
inter-domain isolation.

Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Ian Campbell <Ian.Campbell@eu.citrix.com>
---
 drivers/video/xen-fbfront.c |   96 +++++++++++++++++++++++++++++++++++-------
 1 files changed, 80 insertions(+), 16 deletions(-)

diff --git a/drivers/video/xen-fbfront.c b/drivers/video/xen-fbfront.c
index 56d6061..b43c5c9 100644
--- a/drivers/video/xen-fbfront.c
+++ b/drivers/video/xen-fbfront.c
@@ -11,13 +11,6 @@
  *  more details.
  */
 
-/*
- * TODO:
- *
- * Switch to grant tables when they become capable of dealing with the
- * frame buffer.
- */
-
 #include <linux/console.h>
 #include <linux/kernel.h>
 #include <linux/errno.h>
@@ -32,6 +25,8 @@
 #include <xen/xen.h>
 #include <xen/events.h>
 #include <xen/page.h>
+#include <xen/grant_table.h>
+#include <xen/interface/grant_table.h>
 #include <xen/interface/io/fbif.h>
 #include <xen/interface/io/protocols.h>
 #include <xen/xenbus.h>
@@ -46,6 +41,8 @@ struct xenfb_info {
 	int			irq;
 	struct xenfb_page	*page;
 	unsigned long 		*mfns;
+	grant_ref_t             *mfn_grefs;
+	int                     page_gref;
 	int			update_wanted; /* XENFB_TYPE_UPDATE wanted */
 	int			feature_resize; /* XENFB_TYPE_RESIZE ok */
 	struct xenfb_resize	resize;		/* protected by resize_lock */
@@ -65,7 +62,7 @@ MODULE_PARM_DESC(video,
 
 static void xenfb_make_preferred_console(void);
 static int xenfb_remove(struct xenbus_device *);
-static void xenfb_init_shared_page(struct xenfb_info *, struct fb_info *);
+static void xenfb_init_shared_page(struct xenbus_device *, struct xenfb_info *, struct fb_info *);
 static int xenfb_connect_backend(struct xenbus_device *, struct xenfb_info *);
 static void xenfb_disconnect_backend(struct xenfb_info *);
 
@@ -412,6 +409,7 @@ static int __devinit xenfb_probe(struct xenbus_device *dev,
 	info->x1 = info->y1 = INT_MAX;
 	spin_lock_init(&info->dirty_lock);
 	spin_lock_init(&info->resize_lock);
+	info->page_gref = -1;
 
 	info->fb = vmalloc(fb_size);
 	if (info->fb == NULL)
@@ -474,7 +472,7 @@ static int __devinit xenfb_probe(struct xenbus_device *dev,
 	fb_info->fbdefio = &xenfb_defio;
 	fb_deferred_io_init(fb_info);
 
-	xenfb_init_shared_page(info, fb_info);
+	xenfb_init_shared_page(dev, info, fb_info);
 
 	ret = xenfb_connect_backend(dev, info);
 	if (ret < 0)
@@ -528,7 +526,7 @@ static int xenfb_resume(struct xenbus_device *dev)
 	struct xenfb_info *info = dev_get_drvdata(&dev->dev);
 
 	xenfb_disconnect_backend(info);
-	xenfb_init_shared_page(info, info->fb_info);
+	xenfb_init_shared_page(dev, info, info->fb_info);
 	return xenfb_connect_backend(dev, info);
 }
 
@@ -543,9 +541,25 @@ static int xenfb_remove(struct xenbus_device *dev)
 		fb_dealloc_cmap(&info->fb_info->cmap);
 		framebuffer_release(info->fb_info);
 	}
+	if (info->page_gref >= 0) {
+		int epd = PAGE_SIZE / sizeof(info->mfns[0]);
+		int pdpages = (info->nr_pages + epd - 1) / epd;
+		int i;
+		gnttab_end_foreign_access_ref(info->page_gref, 0);
+		gnttab_free_grant_reference(info->page_gref);
+		for (i = 0; i < pdpages; i++) {
+			gnttab_end_foreign_access_ref(info->mfn_grefs[i], 1);
+			gnttab_free_grant_reference(info->mfn_grefs[i]);
+		}
+		for (i = 0; i < info->nr_pages; i++) {
+			gnttab_end_foreign_access_ref(info->mfns[i], 1);
+			gnttab_free_grant_reference(info->mfns[i]);
+		}
+	}
 	free_page((unsigned long)info->page);
 	vfree(info->mfns);
 	vfree(info->fb);
+	kfree(info->mfn_grefs);
 	kfree(info);
 
 	return 0;
@@ -556,17 +570,63 @@ static unsigned long vmalloc_to_mfn(void *address)
 	return pfn_to_mfn(vmalloc_to_pfn(address));
 }
 
-static void xenfb_init_shared_page(struct xenfb_info *info,
+static void xenfb_init_shared_page(struct xenbus_device *dev,
+                                   struct xenfb_info *info,
 				   struct fb_info *fb_info)
 {
-	int i;
 	int epd = PAGE_SIZE / sizeof(info->mfns[0]);
+	int be_id = dev->otherend_id;
+	int i, ref;
+	unsigned long mfn;
+	grant_ref_t gref_head;
+	int pdpages = (info->nr_pages + epd - 1) / epd;
+	int allpages = info->nr_pages + pdpages + 1;
+
+	int grants = 0;
+	xenbus_scanf(XBT_NIL, dev->otherend, "feature-grants", "%d", &grants);
+
+	if (grants) {
+		int err = gnttab_alloc_grant_references(allpages, &gref_head);
+		info->mfn_grefs = kzalloc(pdpages*sizeof(grant_ref_t), GFP_KERNEL);
+		if (!info->mfn_grefs || err < 0) {
+			info->page_gref = -ENOSPC;
+			if (err >= 0)
+				gnttab_free_grant_references(gref_head);
+			grants = 0;
+		} else {
+			ref = gnttab_claim_grant_reference(&gref_head);
+			mfn = virt_to_mfn(info->page);
+			BUG_ON(ref == -ENOSPC);
+			gnttab_grant_foreign_access_ref(ref, be_id, mfn, 0);
+			info->page_gref = ref;
+		}
+	} else
+		info->page_gref = -ENOENT;
 
 	for (i = 0; i < info->nr_pages; i++)
-		info->mfns[i] = vmalloc_to_mfn(info->fb + i * PAGE_SIZE);
+	{
+		mfn = vmalloc_to_mfn(info->fb + i * PAGE_SIZE);
+		if (grants) {
+			ref = gnttab_claim_grant_reference(&gref_head);
+			BUG_ON(ref == -ENOSPC);
+			gnttab_grant_foreign_access_ref(ref, be_id, mfn, 1);
+			info->mfns[i] = ref;
+		} else
+			info->mfns[i] = mfn;
+	}
 
 	for (i = 0; i * epd < info->nr_pages; i++)
-		info->page->pd[i] = vmalloc_to_mfn(&info->mfns[i * epd]);
+	{
+		mfn = vmalloc_to_mfn(&info->mfns[i * epd]);
+		if (grants) {
+			ref = gnttab_claim_grant_reference(&gref_head);
+			BUG_ON(ref == -ENOSPC);
+			gnttab_grant_foreign_access_ref(ref, be_id, mfn, 1);
+			info->mfn_grefs[i] = ref;
+			info->page->pd[i] = ref;
+		} else
+			info->page->pd[i] = mfn;
+	}
 
 	info->page->width = fb_info->var.xres;
 	info->page->height = fb_info->var.yres;
@@ -599,8 +659,12 @@ static int xenfb_connect_backend(struct xenbus_device *dev,
 		xenbus_dev_fatal(dev, ret, "starting transaction");
 		goto unbind_irq;
 	}
-	ret = xenbus_printf(xbt, dev->nodename, "page-ref", "%lu",
-			    virt_to_mfn(info->page));
+	if (info->page_gref < 0)
+		ret = xenbus_printf(xbt, dev->nodename, "page-ref", "%lu",
+			            virt_to_mfn(info->page));
+	else
+		ret = xenbus_printf(xbt, dev->nodename, "page-gref", "%u",
+				    info->page_gref);
 	if (ret)
 		goto error_xenbus;
 	ret = xenbus_printf(xbt, dev->nodename, "event-channel", "%u",
-- 
1.7.1

Re: [PATCH 2/4] xen-kbdfront: Add grant reference for shared page

[Dmitry Torokhov]

On Tue, Mar 15, 2011 at 10:11:13AM -0400, Konrad Rzeszutek Wilk wrote:
> From: Daniel De Graaf <dgdegra@tycho.nsa.gov>
> 
> Without a grant reference, full access to the domain's memory is
> required to use the shared page. Add an additional parameter in
> xenstore to allow grant mapping to be used.
> 
> Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
> Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

You are passing the patch on so it should be Signed-off-by...

It is independent of the other 2 so I can pick it up and merge (so that
we do not have conflicts with move), right?

-- 
Dmitry

Re: [PATCH 2/4] xen-kbdfront: Add grant reference for shared page

[Konrad Rzeszutek Wilk]

On Tue, Mar 15, 2011 at 10:34:26PM -0700, Dmitry Torokhov wrote:
> On Tue, Mar 15, 2011 at 10:11:13AM -0400, Konrad Rzeszutek Wilk wrote:
> > From: Daniel De Graaf <dgdegra@tycho.nsa.gov>
> > 
> > Without a grant reference, full access to the domain's memory is
> > required to use the shared page. Add an additional parameter in
> > xenstore to allow grant mapping to be used.
> > 
> > Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
> > Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> 
> You are passing the patch on so it should be Signed-off-by...

Oh, somehow I thought that I was suppose to change my SOB to ACK
since it would now go through your tree.

> 
> It is independent of the other 2 so I can pick it up and merge (so that
> we do not have conflicts with move), right?

Yes.

> 
> -- 
> Dmitry

Re: [Xen-devel] [PATCH 2/4] xen-kbdfront: Add grant reference for shared page

[Konrad Rzeszutek Wilk]

On Tue, Mar 15, 2011 at 10:11:13AM -0400, Konrad Rzeszutek Wilk wrote:
> From: Daniel De Graaf <dgdegra@tycho.nsa.gov>
> 
> Without a grant reference, full access to the domain's memory is
> required to use the shared page. Add an additional parameter in
> xenstore to allow grant mapping to be used.
> 
> Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
> Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Replace Acked-by by
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

please.

Re: [Xen-devel] [PATCH 3/4] xen-fbfront: Use grant references when requested

[Konrad Rzeszutek Wilk]

On Tue, Mar 15, 2011 at 10:11:14AM -0400, Konrad Rzeszutek Wilk wrote:
> From: Daniel De Graaf <dgdegra@tycho.nsa.gov>
> 
> The current version of the Xen framebuffer API passes MFNs directly
> to the backend driver, which requires the backend to have full access
> to this domain's memory. Add a parameter in xenbus to request the use of
> grant entries instead, which are slightly slower to map but provide
> inter-domain isolation.
> 
> Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
> Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Replace Acked-by by Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
please.

Re: [Xen-devel] [PATCH 1/4] xen-fbfront: Read width/height from backend

[Konrad Rzeszutek Wilk]

On Tue, Mar 15, 2011 at 10:11:12AM -0400, Konrad Rzeszutek Wilk wrote:
> From: Daniel De Graaf <dgdegra@tycho.nsa.gov>
> 
> This allows the backend driver to specify the size of the framebuffer
> instead of requiring it to be on the kernel command line.
> 
> Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
> Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Replace Acked-by by Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
please.