Currently, the only user of vhost_log_write() is vhost-net. The 'len'
argument prevents logging of pages that are not tainted by the RX path.
Adjustments are needed since more drivers (i.e. vhost-scsi) begin using
vhost_log_write(). So far vhost-net RX path may only partially use pages
shared via the last vring descriptor. Unlike vhost-net, vhost-scsi always
logs all pages shared via vring descriptors. To accommodate this,
use (len == U64_MAX) to indicate whether the driver would log all pages of
vring descriptors, or only pages that are tainted by the driver.
In addition, removes BUG().
Suggested-by: Joao Martins <joao.m.mart...@oracle.com>
Signed-off-by: Dongli Zhang <dongli.zh...@oracle.com>
---
Changed since v2:
- Document parameters of vhost_log_write().
- Use (len == U64_MAX) to indicate whether log all pages, instead of
introducing a new parameter.
drivers/vhost/vhost.c | 28 ++++++++++++++++++++--------
1 file changed, 20 insertions(+), 8 deletions(-)
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 9ac25d08f473..494b3da5423a 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -2304,6 +2304,19 @@ static int log_used(struct vhost_virtqueue *vq, u64
used_offset, u64 len)
return 0;
}
+/*
+ * vhost_log_write() - Log in dirty page bitmap
+ * @vq: vhost virtqueue.
+ * @log: Array of dirty memory in GPA.
+ * @log_num: Size of vhost_log arrary.
+ * @len: The total length of memory buffer to log in the dirty bitmap.
+ * Some drivers may only partially use pages shared via the last
+ * vring descriptor (i.e. vhost-net RX buffer).
+ * Use (len == U64_MAX) to indicate the driver would log all
+ * pages of vring descriptors.
+ * @iov: Array of dirty memory in HVA.
+ * @count: Size of iovec array.
+ */
int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
unsigned int log_num, u64 len, struct iovec *iov, int count)
{
@@ -2327,15 +2340,14 @@ int vhost_log_write(struct vhost_virtqueue *vq, struct
vhost_log *log,
r = log_write(vq->log_base, log[i].addr, l);
if (r < 0)
return r;
- len -= l;
- if (!len) {
- if (vq->log_ctx)
- eventfd_signal(vq->log_ctx);
- return 0;
- }
+
+ if (len != U64_MAX)
+ len -= l;
}
- /* Length written exceeds what we have stored. This is a bug. */
- BUG();
+
+ if (vq->log_ctx)
+ eventfd_signal(vq->log_ctx);
+
return 0;
}
EXPORT_SYMBOL_GPL(vhost_log_write);
--
2.39.3
