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Re: [Xen-devel] [PATCH v4 2/2] qdisk - hw/block/xen_disk: grant copy implementation
On 08/09/2016 06:56 PM, Anthony PERARD wrote:
On Tue, Aug 02, 2016 at 04:06:30PM +0200, 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.
Signed-off-by: Paulina Szubarczyk <paulinaszubarczyk@xxxxxxxxx>
---
Changes since v3:
- qemu_memalign/qemu_free is used instead function allocating
memory from xc.
- removed the get_buffer function instead there is a direct call
to qemu_memalign.
- moved ioreq_copy for write operation to ioreq_runio_qemu_aio.
- added struct xengnttab_grant_copy_segment_t and stub in
xen_common.h for version of xen earlier then 480.
- added checking for version 480 to configure. The test repeats
all the operation that are required for version < 480 and
checks if xengnttab_grant_copy() is implemented.
* 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 | 56 +++++++++++++++++
hw/block/xen_disk.c | 142 ++++++++++++++++++++++++++++++++++++++++++--
include/hw/xen/xen_common.h | 25 ++++++++
3 files changed, 218 insertions(+), 5 deletions(-)
diff --git a/configure b/configure
index f57fcc6..b5bf7d4 100755
--- a/configure
+++ b/configure
@@ -1956,6 +1956,62 @@ EOF
/*
* If we have stable libs the we don't want the libxc compat
* layers, regardless of what CFLAGS we may have been given.
+ *
+ * Also, check if xengnttab_grant_copy_segment_t is defined and
+ * grant copy operation is implemented.
+ */
+#undef XC_WANT_COMPAT_EVTCHN_API
+#undef XC_WANT_COMPAT_GNTTAB_API
+#undef XC_WANT_COMPAT_MAP_FOREIGN_API
+#include <xenctrl.h>
+#include <xenstore.h>
+#include <xenevtchn.h>
+#include <xengnttab.h>
+#include <xenforeignmemory.h>
+#include <stdint.h>
+#include <xen/hvm/hvm_info_table.h>
+#if !defined(HVM_MAX_VCPUS)
+# error HVM_MAX_VCPUS not defined
+#endif
+int main(void) {
+ xc_interface *xc = NULL;
+ xenforeignmemory_handle *xfmem;
+ xenevtchn_handle *xe;
+ xengnttab_handle *xg;
+ xen_domain_handle_t handle;
+ xengnttab_grant_copy_segment_t* seg = NULL;
+
+ xs_daemon_open();
+
+ xc = xc_interface_open(0, 0, 0);
+ xc_hvm_set_mem_type(0, 0, HVMMEM_ram_ro, 0, 0);
+ xc_domain_add_to_physmap(0, 0, XENMAPSPACE_gmfn, 0, 0);
+ xc_hvm_inject_msi(xc, 0, 0xf0000000, 0x00000000);
+ xc_hvm_create_ioreq_server(xc, 0, HVM_IOREQSRV_BUFIOREQ_ATOMIC, NULL);
+ xc_domain_create(xc, 0, handle, 0, NULL, NULL);
+
+ xfmem = xenforeignmemory_open(0, 0);
+ xenforeignmemory_map(xfmem, 0, 0, 0, 0, 0);
+
+ xe = xenevtchn_open(0, 0);
+ xenevtchn_fd(xe);
+
+ xg = xengnttab_open(0, 0);
+ xengnttab_map_grant_ref(xg, 0, 0, 0);
+ xengnttab_grant_copy(xg, 0, seg);
+
+ return 0;
+}
+EOF
+ compile_prog "" "$xen_libs $xen_stable_libs"
+ then
+ xen_ctrl_version=480
+ xen=yes
+ elif
+ cat > $TMPC <<EOF &&
+/*
+ * If we have stable libs the we don't want the libxc compat
+ * layers, regardless of what CFLAGS we may have been given.
*/
#undef XC_WANT_COMPAT_EVTCHN_API
#undef XC_WANT_COMPAT_GNTTAB_API
diff --git a/hw/block/xen_disk.c b/hw/block/xen_disk.c
index 3b8ad33..2dd1464 100644
--- a/hw/block/xen_disk.c
+++ b/hw/block/xen_disk.c
@@ -119,6 +119,9 @@ struct XenBlkDev {
unsigned int persistent_gnt_count;
unsigned int max_grants;
+ /* Grant copy */
+ gboolean feature_grant_copy;
+
/* qemu block driver */
DriveInfo *dinfo;
BlockBackend *blk;
@@ -489,6 +492,95 @@ static int ioreq_map(struct ioreq *ioreq)
return 0;
}
+static void free_buffers(struct ioreq *ioreq)
+{
+ int i;
+
+ for (i = 0; i < ioreq->v.niov; i++) {
+ ioreq->page[i] = NULL;
+ }
+
+ qemu_vfree(ioreq->pages);
+}
+
+static int ioreq_init_copy_buffers(struct ioreq *ioreq)
+{
+ int i;
+
+ if (ioreq->v.niov == 0) {
+ return 0;
+ }
+
+ ioreq->pages = qemu_memalign(XC_PAGE_SIZE, ioreq->v.niov * XC_PAGE_SIZE);
+ if (!ioreq->pages) {
qemu_memalign never returns NULL, you don't have to check.
+ 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 = ioreq->page[i];
+ }
+
+ return 0;
+}
+
+static int ioreq_copy(struct ioreq *ioreq)
+{
+ xengnttab_handle *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)
@@ -511,8 +603,29 @@ 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:
@@ -538,8 +651,20 @@ static int ioreq_runio_qemu_aio(struct ioreq *ioreq)
{
struct XenBlkDev *blkdev = ioreq->blkdev;
- if (ioreq->req.nr_segments && ioreq_map(ioreq) == -1) {
- goto err_no_map;
+ 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;
+ }
+ }
+
+ } else {
+ if (ioreq->req.nr_segments && ioreq_map(ioreq)) {
+ goto err;
+ }
}
ioreq->aio_inflight++;
@@ -582,6 +707,9 @@ static int ioreq_runio_qemu_aio(struct ioreq *ioreq)
}
default:
/* unknown operation (shouldn't happen -- parse catches this) */
+ if (!ioreq->blkdev->feature_grant_copy) {
+ ioreq_unmap(ioreq);
+ }
goto err;
}
@@ -590,8 +718,6 @@ static int ioreq_runio_qemu_aio(struct ioreq *ioreq)
return 0;
err:
- ioreq_unmap(ioreq);
-err_no_map:
ioreq_finish(ioreq);
ioreq->status = BLKIF_RSP_ERROR;
return -1;
@@ -1032,6 +1158,12 @@ 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,
diff --git a/include/hw/xen/xen_common.h b/include/hw/xen/xen_common.h
index 640c31e..e80c61f 100644
--- a/include/hw/xen/xen_common.h
+++ b/include/hw/xen/xen_common.h
@@ -25,6 +25,31 @@
*/
/* Xen 4.2 through 4.6 */
+#if CONFIG_XEN_CTRL_INTERFACE_VERSION < 480
+
+struct xengnttab_grant_copy_segment {
+ union xengnttab_copy_ptr {
+ void *virt;
+ struct {
+ uint32_t ref;
+ uint16_t offset;
+ uint16_t domid;
+ } foreign;
+ } source, dest;
+ uint16_t len;
+ uint16_t flags;
+ int16_t status;
+};
I don't think it's a good idee to define a struct that is not going to
be used, and does not belong here. The typedef is OK.
I added it since it is needed to know all the fields of that struct in
ioreq_copy but if I could replace that function with stubs I will do that.
In xen_disk.c, you could use "#if CONFIG_XEN_CTRL_INTERFACE_VERSION ..."
around free_buffers, ioreq_init_copy_buffers and ioreq_copy, and replace
them by stubs when Xen does not support grant copy. I think that would
be better.
Also, could you try to compile again xen unstable, without your other patch?
Right now, it does not compile.
That is true, I am sorry. I need to add the headers that are included in
the
#else /* CONFIG_XEN_CTRL_INTERFACE_VERSION >= 471 */
#include <xenevtchn.h>
#include <xengnttab.h>
#include <xenforeignmemory.h>
#endif
May I move that part to separate #if CONFIG_XEN_CTRL_INTERFACE_VERSION
>= 471 in that header?
+typedef struct xengnttab_grant_copy_segment xengnttab_grant_copy_segment_t;
+
+static inline int xengnttab_grant_copy(xengnttab_handle *xgt, uint32_t count,
+ xengnttab_grant_copy_segment_t *segs)
+{
+ return -1;
return -ENOSYS would be more appropriate.
Otherwise, the patch looks good.
Thanks,
Thank you,
Paulina
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