From: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
This patch adds a vhost_skip_iovec_bytes() helper for skipping ahead
a number of bytes into the passed *iov_in + off_in, saving the current
**iov_out + off_out so it may be used by the caller.
This is useful for virtio-scsi READs when needing to skip ahead of
the starting response header bytes, and when T10_PI is enabled to
skip ahead of any preceeding protection payload to the start of
data payload.
It also checks max_niov to ensure the passed number of bytes does
not exceed what vhost_get_vq_desc() reports as the total number of
iovecs into vhost_virtqueue->iov[] for a individual request.
Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
---
drivers/vhost/scsi.c | 40 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 40 insertions(+)
diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index ecbd567..d888bd9 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -1078,6 +1078,46 @@ vhost_scsi_send_bad_target(struct vhost_scsi *vs,
pr_err("Faulted on virtio_scsi_cmd_resp\n");
}
+int vhost_skip_iovec_bytes(size_t bytes, int max_niov,
+ struct iovec *iov_in, size_t off_in,
+ struct iovec **iov_out, size_t *off_out)
+{
+ int i = 0;
+
+ *off_out = 0;
+
+ if (!bytes)
+ return 0;
+
+ while (bytes) {
+ size_t iov_len = iov_in[i].iov_len - off_in;
+ size_t len = min(iov_len, bytes);
+
+ if (bytes -= len) {
+ if (++i == max_niov) {
+ pr_err("%s exceeded max_niov: %d\n",
+ __func__, max_niov);
+ return -EINVAL;
+ }
+ off_in = 0;
+ continue;
+ }
+ if (iov_len > len) {
+ *iov_out = &iov_in[i];
+ *off_out = len;
+ } else if (iov_len == len) {
+ if (++i == max_niov) {
+ pr_err("%s exceeded max_niov: %d\n",
+ __func__, max_niov);
+ return -EINVAL;
+ }
+ *iov_out = &iov_in[i];
+ *off_out = 0;
+ }
+ }
+ return i;
+}
+
static void
vhost_scsi_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq)
{
--
1.9.1
--
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