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Re: [Xen-devel] [PATCH v3 2/2] qdisk - hw/block/xen_disk: grant copy implementation
On 06/22/2016 10:38 AM, Paulina Szubarczyk wrote:
Copy data operated on during request from/to local buffers to/from
the grant references.
Before grant copy operation local buffers must be allocated what is
done by calling ioreq_init_copy_buffers. For the 'read' operation,
first, the qemu device invokes the read operation on local buffers
and on the completion grant copy is called and buffers are freed.
For the 'write' operation grant copy is performed before invoking
write by qemu device.
A new value 'feature_grant_copy' is added to recognize when the
grant copy operation is supported by a guest.
The body of the function 'ioreq_runio_qemu_aio' is moved to
'ioreq_runio_qemu_aio_blk' and in the 'ioreq_runio_qemu_aio' depending
on the support for grant copy according checks, initialization, grant
operation are made, then the 'ioreq_runio_qemu_aio_blk' function is
called.
Signed-off-by: Paulina Szubarczyk <paulinaszubarczyk@xxxxxxxxx>
---
Changes since v2:
- to use the xengnttab_* function directly added -lxengnttab to configure
and include <xengnttab.h> in include/hw/xen/xen_common.h
- in ioreq_copy removed an out path, changed a log level, made explicit
assignement to 'xengnttab_copy_grant_segment'
* I did not change the way of testing if grant_copy operation is implemented.
As far as I understand if the code from gnttab_unimp.c is used then the
gnttab
device is unavailable and the handler to gntdev would be invalid. But
if the handler is valid then the ioctl should return operation unimplemented
if the gntdev does not implement the operation.
configure | 2 +-
hw/block/xen_disk.c | 171 ++++++++++++++++++++++++++++++++++++++++----
include/hw/xen/xen_common.h | 2 +
3 files changed, 162 insertions(+), 13 deletions(-)
diff --git a/configure b/configure
index e41876a..355d3fa 100755
--- a/configure
+++ b/configure
@@ -1843,7 +1843,7 @@ fi
# xen probe
if test "$xen" != "no" ; then
- xen_libs="-lxenstore -lxenctrl -lxenguest"
+ xen_libs="-lxenstore -lxenctrl -lxenguest -lxengnttab"
# First we test whether Xen headers and libraries are available.
# If no, we are done and there is no Xen support.
diff --git a/hw/block/xen_disk.c b/hw/block/xen_disk.c
index 37e14d1..4eca06a 100644
--- a/hw/block/xen_disk.c
+++ b/hw/block/xen_disk.c
@@ -131,6 +131,9 @@ struct XenBlkDev {
unsigned int persistent_gnt_count;
unsigned int max_grants;
+ /* Grant copy */
+ gboolean feature_grant_copy;
+
/* qemu block driver */
DriveInfo *dinfo;
BlockBackend *blk;
@@ -500,6 +503,99 @@ static int ioreq_map(struct ioreq *ioreq)
return 0;
}
+static void* get_buffer(int count)
+{
+ return xc_memalign(xen_xc, XC_PAGE_SIZE, count*XC_PAGE_SIZE);
+}
+
+static void free_buffers(struct ioreq *ioreq)
+{
+ int i;
+
+ for (i = 0; i < ioreq->v.niov; i++) {
+ ioreq->page[i] = NULL;
+ }
+
+ free(ioreq->pages);
+}
+
+static int ioreq_init_copy_buffers(struct ioreq *ioreq) {
+ int i;
+
+ if (ioreq->v.niov == 0) {
+ return 0;
+ }
+
+ ioreq->pages = get_buffer(ioreq->v.niov);
+ if (!ioreq->pages) {
+ return -1;
+ }
+
+ for (i = 0; i < ioreq->v.niov; i++) {
+ ioreq->page[i] = ioreq->pages + i*XC_PAGE_SIZE;
+ ioreq->v.iov[i].iov_base += (uintptr_t)ioreq->page[i];
+ }
+
+ return 0;
+}
+
+static int ioreq_copy(struct ioreq *ioreq)
+{
+ XenGnttab gnt = ioreq->blkdev->xendev.gnttabdev;
+ xengnttab_grant_copy_segment_t segs[BLKIF_MAX_SEGMENTS_PER_REQUEST];
+ int i, count = 0, r, rc;
+ int64_t file_blk = ioreq->blkdev->file_blk;
+
+ if (ioreq->v.niov == 0) {
+ return 0;
+ }
+
+ count = ioreq->v.niov;
+
+ for (i = 0; i < count; i++) {
+
+ if (ioreq->req.operation == BLKIF_OP_READ) {
+ segs[i].flags = GNTCOPY_dest_gref;
+ segs[i].dest.foreign.ref = ioreq->refs[i];
+ segs[i].dest.foreign.domid = ioreq->domids[i];
+ segs[i].dest.foreign.offset = ioreq->req.seg[i].first_sect *
file_blk;
+ segs[i].source.virt = ioreq->v.iov[i].iov_base;
+ } else {
+ segs[i].flags = GNTCOPY_source_gref;
+ segs[i].source.foreign.ref = ioreq->refs[i];
+ segs[i].source.foreign.domid = ioreq->domids[i];
+ segs[i].source.foreign.offset = ioreq->req.seg[i].first_sect *
file_blk;
+ segs[i].dest.virt = ioreq->v.iov[i].iov_base;
+ }
+ segs[i].len = (ioreq->req.seg[i].last_sect
+ - ioreq->req.seg[i].first_sect + 1) * file_blk;
+
+ }
+
+ rc = xengnttab_grant_copy(gnt, count, segs);
+
+ if (rc) {
+ xen_be_printf(&ioreq->blkdev->xendev, 0,
+ "failed to copy data %d \n", rc);
+ ioreq->aio_errors++;
+ return -1;
+ } else {
+ r = 0;
+ }
+
+ for (i = 0; i < count; i++) {
+ if (segs[i].status != GNTST_okay) {
+ xen_be_printf(&ioreq->blkdev->xendev, 3,
+ "failed to copy data %d for gref %d, domid %d\n", rc,
+ ioreq->refs[i], ioreq->domids[i]);
+ ioreq->aio_errors++;
+ r = -1;
+ }
+ }
+
+ return r;
+}
+
static int ioreq_runio_qemu_aio(struct ioreq *ioreq);
static void qemu_aio_complete(void *opaque, int ret)
@@ -528,8 +624,31 @@ static void qemu_aio_complete(void *opaque, int ret)
return;
}
+ if (ioreq->blkdev->feature_grant_copy) {
+ switch (ioreq->req.operation) {
+ case BLKIF_OP_READ:
+ /* in case of failure ioreq->aio_errors is increased */
+ ioreq_copy(ioreq);
+ free_buffers(ioreq);
+ break;
+ case BLKIF_OP_WRITE:
+ case BLKIF_OP_FLUSH_DISKCACHE:
+ if (!ioreq->req.nr_segments) {
+ break;
+ }
+ free_buffers(ioreq);
+ break;
+ default:
+ break;
+ }
+ }
+
ioreq->status = ioreq->aio_errors ? BLKIF_RSP_ERROR : BLKIF_RSP_OKAY;
- ioreq_unmap(ioreq);
+
+ if (!ioreq->blkdev->feature_grant_copy) {
+ ioreq_unmap(ioreq);
+ }
+
ioreq_finish(ioreq);
switch (ioreq->req.operation) {
case BLKIF_OP_WRITE:
@@ -547,14 +666,42 @@ static void qemu_aio_complete(void *opaque, int ret)
qemu_bh_schedule(ioreq->blkdev->bh);
}
+static int ioreq_runio_qemu_aio_blk(struct ioreq *ioreq);
+
static int ioreq_runio_qemu_aio(struct ioreq *ioreq)
{
- struct XenBlkDev *blkdev = ioreq->blkdev;
+ if (ioreq->blkdev->feature_grant_copy) {
+
+ ioreq_init_copy_buffers(ioreq);
+ if (ioreq->req.nr_segments && (ioreq->req.operation == BLKIF_OP_WRITE
||
+ ioreq->req.operation == BLKIF_OP_FLUSH_DISKCACHE)) {
+ if (ioreq_copy(ioreq)) {
+ free_buffers(ioreq);
+ goto err;
+ }
+ }
+ if (ioreq_runio_qemu_aio_blk(ioreq)) goto err;
+
+ } else {
- if (ioreq->req.nr_segments && ioreq_map(ioreq) == -1) {
- goto err_no_map;
+ if (ioreq->req.nr_segments && ioreq_map(ioreq)) goto err;
+ if (ioreq_runio_qemu_aio_blk(ioreq)) {
+ ioreq_unmap(ioreq);
+ goto err;
+ }
}
+ return 0;
+err:
+ ioreq_finish(ioreq);
+ ioreq->status = BLKIF_RSP_ERROR;
+ return -1;
+}
+
+static int ioreq_runio_qemu_aio_blk(struct ioreq *ioreq)
+{
+ struct XenBlkDev *blkdev = ioreq->blkdev;
+
ioreq->aio_inflight++;
if (ioreq->presync) {
blk_aio_flush(ioreq->blkdev->blk, qemu_aio_complete, ioreq);
@@ -594,19 +741,12 @@ static int ioreq_runio_qemu_aio(struct ioreq *ioreq)
}
default:
/* unknown operation (shouldn't happen -- parse catches this) */
- goto err;
+ return -1;
}
qemu_aio_complete(ioreq, 0);
return 0;
-
-err:
- ioreq_unmap(ioreq);
-err_no_map:
- ioreq_finish(ioreq);
- ioreq->status = BLKIF_RSP_ERROR;
- return -1;
}
static int blk_send_response_one(struct ioreq *ioreq)
@@ -1020,10 +1160,17 @@ static int blk_connect(struct XenDevice *xendev)
xen_be_bind_evtchn(&blkdev->xendev);
+ blkdev->feature_grant_copy =
+ (xengnttab_grant_copy(blkdev->xendev.gnttabdev, 0, NULL) == 0);
+
+ xen_be_printf(&blkdev->xendev, 3, "grant copy operation %s\n",
+ blkdev->feature_grant_copy ? "enabled" : "disabled");
+
xen_be_printf(&blkdev->xendev, 1, "ok: proto %s, ring-ref %d, "
"remote port %d, local port %d\n",
blkdev->xendev.protocol, blkdev->ring_ref,
blkdev->xendev.remote_port, blkdev->xendev.local_port);
+
return 0;
}
diff --git a/include/hw/xen/xen_common.h b/include/hw/xen/xen_common.h
index 4ac0c6f..bed5307 100644
--- a/include/hw/xen/xen_common.h
+++ b/include/hw/xen/xen_common.h
@@ -14,6 +14,8 @@
#endif
#include <xen/io/xenbus.h>
+#include <xengnttab.h>
+
#include "hw/hw.h"
#include "hw/xen/xen.h"
#include "hw/pci/pci.h"
When it comes to that second part of the patch, should I do some changes
here?
Paulina
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