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Re: [Xen-devel] [PATCH v4 2/2] qdisk - hw/block/xen_disk: grant copy implementation
On 08/08/2016 01:11 PM, Roger Pau Monné 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>
Thanks, this is looking good, just a couple of minor comments below.
Thank you for the review, I will apply the comments.
---
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);
I don't think you need to check xengnttab_map_grant_ref, just
xengnttab_grant_copy should be enough? Since xengnttab_grant_copy was added
later you can assume xengnttab_map_grant_ref will be there.
+ 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) {
+ 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;
Why do you need to initialize count to 0 here? A couple of lines below you
inconditionally set it to ioreq->v.niov.
+ 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;
+ }
Do you really need both r and rc here? I think you could just have rc and
use it below also.
+ 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)
Roger.
Paulina
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