[PATCH v3 00/21] xen: simplify frontend side ring setup

[PATCH v3 00/21] xen: simplify frontend side ring setup

[Juergen Gross]

Many Xen PV frontends share similar code for setting up a ring page
(allocating and granting access for the backend) and for tearing it
down.

Create new service functions doing all needed steps in one go.

This requires all frontends to use a common value for an invalid
grant reference in order to make the functions idempotent.

Changes in V3:
- new patches 1 and 2, comments addressed

Changes in V2:
- new patch 9 and related changes in patches 10-18

Juergen Gross (21):
  xen: update grant_table.h
  xen/grant-table: never put a reserved grant on the free list
  xen/blkfront: switch blkfront to use INVALID_GRANT_REF
  xen/netfront: switch netfront to use INVALID_GRANT_REF
  xen/scsifront: remove unused GRANT_INVALID_REF definition
  xen/usb: switch xen-hcd to use INVALID_GRANT_REF
  xen/drm: switch xen_drm_front to use INVALID_GRANT_REF
  xen/sound: switch xen_snd_front to use INVALID_GRANT_REF
  xen/dmabuf: switch gntdev-dmabuf to use INVALID_GRANT_REF
  xen/shbuf: switch xen-front-pgdir-shbuf to use INVALID_GRANT_REF
  xen: update ring.h
  xen/xenbus: add xenbus_setup_ring() service function
  xen/blkfront: use xenbus_setup_ring() and xenbus_teardown_ring()
  xen/netfront: use xenbus_setup_ring() and xenbus_teardown_ring()
  xen/tpmfront: use xenbus_setup_ring() and xenbus_teardown_ring()
  xen/drmfront: use xenbus_setup_ring() and xenbus_teardown_ring()
  xen/pcifront: use xenbus_setup_ring() and xenbus_teardown_ring()
  xen/scsifront: use xenbus_setup_ring() and xenbus_teardown_ring()
  xen/usbfront: use xenbus_setup_ring() and xenbus_teardown_ring()
  xen/sndfront: use xenbus_setup_ring() and xenbus_teardown_ring()
  xen/xenbus: eliminate xenbus_grant_ring()

 drivers/block/xen-blkfront.c                |  57 +++----
 drivers/char/tpm/xen-tpmfront.c             |  18 +--
 drivers/gpu/drm/xen/xen_drm_front.h         |   9 --
 drivers/gpu/drm/xen/xen_drm_front_evtchnl.c |  43 ++----
 drivers/net/xen-netfront.c                  |  85 ++++-------
 drivers/pci/xen-pcifront.c                  |  19 +--
 drivers/scsi/xen-scsifront.c                |  31 +---
 drivers/usb/host/xen-hcd.c                  |  65 ++------
 drivers/xen/gntdev-dmabuf.c                 |  13 +-
 drivers/xen/grant-table.c                   |  12 +-
 drivers/xen/xen-front-pgdir-shbuf.c         |  18 +--
 drivers/xen/xenbus/xenbus_client.c          |  82 +++++++---
 include/xen/grant_table.h                   |   2 -
 include/xen/interface/grant_table.h         | 161 ++++++++++++--------
 include/xen/interface/io/ring.h             |  19 ++-
 include/xen/xenbus.h                        |   4 +-
 sound/xen/xen_snd_front_evtchnl.c           |  44 ++----
 sound/xen/xen_snd_front_evtchnl.h           |   9 --
 18 files changed, 287 insertions(+), 404 deletions(-)

-- 
2.35.3

[PATCH v3 03/21] xen/blkfront: switch blkfront to use INVALID_GRANT_REF

[Juergen Gross]

Instead of using a private macro for an invalid grant reference use
the common one.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
 drivers/block/xen-blkfront.c | 26 ++++++++++++--------------
 1 file changed, 12 insertions(+), 14 deletions(-)

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 003056d4f7f5..7f35e30e626a 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -229,8 +229,6 @@ static unsigned int nr_minors;
 static unsigned long *minors;
 static DEFINE_SPINLOCK(minor_lock);
 
-#define GRANT_INVALID_REF	0
-
 #define PARTS_PER_DISK		16
 #define PARTS_PER_EXT_DISK      256
 
@@ -321,7 +319,7 @@ static int fill_grant_buffer(struct blkfront_ring_info *rinfo, int num)
 			gnt_list_entry->page = granted_page;
 		}
 
-		gnt_list_entry->gref = GRANT_INVALID_REF;
+		gnt_list_entry->gref = INVALID_GRANT_REF;
 		list_add(&gnt_list_entry->node, &rinfo->grants);
 		i++;
 	}
@@ -350,7 +348,7 @@ static struct grant *get_free_grant(struct blkfront_ring_info *rinfo)
 					  node);
 	list_del(&gnt_list_entry->node);
 
-	if (gnt_list_entry->gref != GRANT_INVALID_REF)
+	if (gnt_list_entry->gref != INVALID_GRANT_REF)
 		rinfo->persistent_gnts_c--;
 
 	return gnt_list_entry;
@@ -372,7 +370,7 @@ static struct grant *get_grant(grant_ref_t *gref_head,
 	struct grant *gnt_list_entry = get_free_grant(rinfo);
 	struct blkfront_info *info = rinfo->dev_info;
 
-	if (gnt_list_entry->gref != GRANT_INVALID_REF)
+	if (gnt_list_entry->gref != INVALID_GRANT_REF)
 		return gnt_list_entry;
 
 	/* Assign a gref to this page */
@@ -396,7 +394,7 @@ static struct grant *get_indirect_grant(grant_ref_t *gref_head,
 	struct grant *gnt_list_entry = get_free_grant(rinfo);
 	struct blkfront_info *info = rinfo->dev_info;
 
-	if (gnt_list_entry->gref != GRANT_INVALID_REF)
+	if (gnt_list_entry->gref != INVALID_GRANT_REF)
 		return gnt_list_entry;
 
 	/* Assign a gref to this page */
@@ -1221,7 +1219,7 @@ static void blkif_free_ring(struct blkfront_ring_info *rinfo)
 		list_for_each_entry_safe(persistent_gnt, n,
 					 &rinfo->grants, node) {
 			list_del(&persistent_gnt->node);
-			if (persistent_gnt->gref != GRANT_INVALID_REF) {
+			if (persistent_gnt->gref != INVALID_GRANT_REF) {
 				gnttab_end_foreign_access(persistent_gnt->gref,
 							  0UL);
 				rinfo->persistent_gnts_c--;
@@ -1283,9 +1281,9 @@ static void blkif_free_ring(struct blkfront_ring_info *rinfo)
 
 	/* Free resources associated with old device channel. */
 	for (i = 0; i < info->nr_ring_pages; i++) {
-		if (rinfo->ring_ref[i] != GRANT_INVALID_REF) {
+		if (rinfo->ring_ref[i] != INVALID_GRANT_REF) {
 			gnttab_end_foreign_access(rinfo->ring_ref[i], 0);
-			rinfo->ring_ref[i] = GRANT_INVALID_REF;
+			rinfo->ring_ref[i] = INVALID_GRANT_REF;
 		}
 	}
 	free_pages_exact(rinfo->ring.sring,
@@ -1475,7 +1473,7 @@ static int blkif_completion(unsigned long *id,
 			 * to the tail of the list, so it will not be picked
 			 * again unless we run out of persistent grants.
 			 */
-			s->grants_used[i]->gref = GRANT_INVALID_REF;
+			s->grants_used[i]->gref = INVALID_GRANT_REF;
 			list_add_tail(&s->grants_used[i]->node, &rinfo->grants);
 		}
 	}
@@ -1500,7 +1498,7 @@ static int blkif_completion(unsigned long *id,
 					indirect_page = s->indirect_grants[i]->page;
 					list_add(&indirect_page->lru, &rinfo->indirect_pages);
 				}
-				s->indirect_grants[i]->gref = GRANT_INVALID_REF;
+				s->indirect_grants[i]->gref = INVALID_GRANT_REF;
 				list_add_tail(&s->indirect_grants[i]->node, &rinfo->grants);
 			}
 		}
@@ -1687,7 +1685,7 @@ static int setup_blkring(struct xenbus_device *dev,
 	grant_ref_t gref[XENBUS_MAX_RING_GRANTS];
 
 	for (i = 0; i < info->nr_ring_pages; i++)
-		rinfo->ring_ref[i] = GRANT_INVALID_REF;
+		rinfo->ring_ref[i] = INVALID_GRANT_REF;
 
 	sring = alloc_pages_exact(ring_size, GFP_NOIO);
 	if (!sring) {
@@ -2544,13 +2542,13 @@ static void purge_persistent_grants(struct blkfront_info *info)
 
 		list_for_each_entry_safe(gnt_list_entry, tmp, &rinfo->grants,
 					 node) {
-			if (gnt_list_entry->gref == GRANT_INVALID_REF ||
+			if (gnt_list_entry->gref == INVALID_GRANT_REF ||
 			    !gnttab_try_end_foreign_access(gnt_list_entry->gref))
 				continue;
 
 			list_del(&gnt_list_entry->node);
 			rinfo->persistent_gnts_c--;
-			gnt_list_entry->gref = GRANT_INVALID_REF;
+			gnt_list_entry->gref = INVALID_GRANT_REF;
 			list_add_tail(&gnt_list_entry->node, &grants);
 		}
 
-- 
2.35.3

[PATCH v3 13/21] xen/blkfront: use xenbus_setup_ring() and xenbus_teardown_ring()

[Juergen Gross]

Simplify blkfront's ring creation and removal via xenbus_setup_ring()
and xenbus_teardown_ring().

Signed-off-by: Juergen Gross <jgross@suse.com>
---
 drivers/block/xen-blkfront.c | 37 ++++++++----------------------------
 1 file changed, 8 insertions(+), 29 deletions(-)

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 7f35e30e626a..bd7b34f29193 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -1280,15 +1280,8 @@ static void blkif_free_ring(struct blkfront_ring_info *rinfo)
 	flush_work(&rinfo->work);
 
 	/* Free resources associated with old device channel. */
-	for (i = 0; i < info->nr_ring_pages; i++) {
-		if (rinfo->ring_ref[i] != INVALID_GRANT_REF) {
-			gnttab_end_foreign_access(rinfo->ring_ref[i], 0);
-			rinfo->ring_ref[i] = INVALID_GRANT_REF;
-		}
-	}
-	free_pages_exact(rinfo->ring.sring,
-			 info->nr_ring_pages * XEN_PAGE_SIZE);
-	rinfo->ring.sring = NULL;
+	xenbus_teardown_ring((void **)&rinfo->ring.sring, info->nr_ring_pages,
+			     rinfo->ring_ref);
 
 	if (rinfo->irq)
 		unbind_from_irqhandler(rinfo->irq, rinfo);
@@ -1679,30 +1672,16 @@ static int setup_blkring(struct xenbus_device *dev,
 			 struct blkfront_ring_info *rinfo)
 {
 	struct blkif_sring *sring;
-	int err, i;
+	int err;
 	struct blkfront_info *info = rinfo->dev_info;
 	unsigned long ring_size = info->nr_ring_pages * XEN_PAGE_SIZE;
-	grant_ref_t gref[XENBUS_MAX_RING_GRANTS];
-
-	for (i = 0; i < info->nr_ring_pages; i++)
-		rinfo->ring_ref[i] = INVALID_GRANT_REF;
 
-	sring = alloc_pages_exact(ring_size, GFP_NOIO);
-	if (!sring) {
-		xenbus_dev_fatal(dev, -ENOMEM, "allocating shared ring");
-		return -ENOMEM;
-	}
-	SHARED_RING_INIT(sring);
-	FRONT_RING_INIT(&rinfo->ring, sring, ring_size);
-
-	err = xenbus_grant_ring(dev, rinfo->ring.sring, info->nr_ring_pages, gref);
-	if (err < 0) {
-		free_pages_exact(sring, ring_size);
-		rinfo->ring.sring = NULL;
+	err = xenbus_setup_ring(dev, GFP_NOIO, (void **)&sring,
+				info->nr_ring_pages, rinfo->ring_ref);
+	if (err)
 		goto fail;
-	}
-	for (i = 0; i < info->nr_ring_pages; i++)
-		rinfo->ring_ref[i] = gref[i];
+
+	XEN_FRONT_RING_INIT(&rinfo->ring, sring, ring_size);
 
 	err = xenbus_alloc_evtchn(dev, &rinfo->evtchn);
 	if (err)
-- 
2.35.3

Re: [PATCH v3 00/21] xen: simplify frontend side ring setup

[Boris Ostrovsky]

On 5/5/22 4:16 AM, Juergen Gross wrote:
> Many Xen PV frontends share similar code for setting up a ring page
> (allocating and granting access for the backend) and for tearing it
> down.
>
> Create new service functions doing all needed steps in one go.
>
> This requires all frontends to use a common value for an invalid
> grant reference in order to make the functions idempotent.
>
> Changes in V3:
> - new patches 1 and 2, comments addressed
>
> Changes in V2:
> - new patch 9 and related changes in patches 10-18


For the patches that I was explicitly copied on:


Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

Re: [PATCH v3 03/21] xen/blkfront: switch blkfront to use INVALID_GRANT_REF

[Roger Pau Monné]

On Thu, May 05, 2022 at 10:16:22AM +0200, Juergen Gross wrote:
> Instead of using a private macro for an invalid grant reference use
> the common one.
> 
> Signed-off-by: Juergen Gross <jgross@suse.com>

Acked-by: Roger Pau Monné <roger.pau@citrix.com>

Thanks, Roger.

Re: [PATCH v3 13/21] xen/blkfront: use xenbus_setup_ring() and xenbus_teardown_ring()

[Roger Pau Monné]

On Thu, May 05, 2022 at 10:16:32AM +0200, Juergen Gross wrote:
> Simplify blkfront's ring creation and removal via xenbus_setup_ring()
> and xenbus_teardown_ring().
> 
> Signed-off-by: Juergen Gross <jgross@suse.com>

Acked-by: Roger Pau Monné <roger.pau@citrix.com>

Thanks, Roger.

Re: [PATCH v3 00/21] xen: simplify frontend side ring setup

[Oleksandr]

On 05.05.22 11:16, Juergen Gross wrote:

Hello Juergen.



> Many Xen PV frontends share similar code for setting up a ring page
> (allocating and granting access for the backend) and for tearing it
> down.
>
> Create new service functions doing all needed steps in one go.
>
> This requires all frontends to use a common value for an invalid
> grant reference in order to make the functions idempotent.
>
> Changes in V3:
> - new patches 1 and 2, comments addressed
>
> Changes in V2:
> - new patch 9 and related changes in patches 10-18
>
> Juergen Gross (21):
>    xen: update grant_table.h
>    xen/grant-table: never put a reserved grant on the free list
>    xen/blkfront: switch blkfront to use INVALID_GRANT_REF
>    xen/netfront: switch netfront to use INVALID_GRANT_REF
>    xen/scsifront: remove unused GRANT_INVALID_REF definition
>    xen/usb: switch xen-hcd to use INVALID_GRANT_REF
>    xen/drm: switch xen_drm_front to use INVALID_GRANT_REF
>    xen/sound: switch xen_snd_front to use INVALID_GRANT_REF
>    xen/dmabuf: switch gntdev-dmabuf to use INVALID_GRANT_REF
>    xen/shbuf: switch xen-front-pgdir-shbuf to use INVALID_GRANT_REF
>    xen: update ring.h
>    xen/xenbus: add xenbus_setup_ring() service function
>    xen/blkfront: use xenbus_setup_ring() and xenbus_teardown_ring()
>    xen/netfront: use xenbus_setup_ring() and xenbus_teardown_ring()
>    xen/tpmfront: use xenbus_setup_ring() and xenbus_teardown_ring()
>    xen/drmfront: use xenbus_setup_ring() and xenbus_teardown_ring()
>    xen/pcifront: use xenbus_setup_ring() and xenbus_teardown_ring()
>    xen/scsifront: use xenbus_setup_ring() and xenbus_teardown_ring()
>    xen/usbfront: use xenbus_setup_ring() and xenbus_teardown_ring()
>    xen/sndfront: use xenbus_setup_ring() and xenbus_teardown_ring()
>    xen/xenbus: eliminate xenbus_grant_ring()


For the patches that touch PV display (#07, #16), PV sound (#08, #20) 
and shared buffer framework used by both frontends (#10):

Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>


Also I didn't see any issues with these frontends while testing on Arm64 
based board.
So, you can also add:

[Arm64 only]
Tested-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>


Thanks!


>
>   drivers/block/xen-blkfront.c                |  57 +++----
>   drivers/char/tpm/xen-tpmfront.c             |  18 +--
>   drivers/gpu/drm/xen/xen_drm_front.h         |   9 --
>   drivers/gpu/drm/xen/xen_drm_front_evtchnl.c |  43 ++----
>   drivers/net/xen-netfront.c                  |  85 ++++-------
>   drivers/pci/xen-pcifront.c                  |  19 +--
>   drivers/scsi/xen-scsifront.c                |  31 +---
>   drivers/usb/host/xen-hcd.c                  |  65 ++------
>   drivers/xen/gntdev-dmabuf.c                 |  13 +-
>   drivers/xen/grant-table.c                   |  12 +-
>   drivers/xen/xen-front-pgdir-shbuf.c         |  18 +--
>   drivers/xen/xenbus/xenbus_client.c          |  82 +++++++---
>   include/xen/grant_table.h                   |   2 -
>   include/xen/interface/grant_table.h         | 161 ++++++++++++--------
>   include/xen/interface/io/ring.h             |  19 ++-
>   include/xen/xenbus.h                        |   4 +-
>   sound/xen/xen_snd_front_evtchnl.c           |  44 ++----
>   sound/xen/xen_snd_front_evtchnl.h           |   9 --
>   18 files changed, 287 insertions(+), 404 deletions(-)
>
-- 
Regards,

Oleksandr Tyshchenko