On Mon, Feb 01, 2021 at 01:40:01PM +0800, Jason Wang wrote:
On 2021/1/28 下午10:41, Stefano Garzarella wrote:
__vringh_iov() overwrites the contents of riov and wiov, in fact it
resets the 'i' and 'used' fields, but also the consumed field should
be reset to avoid an inconsistent state.
Signed-off-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
I had a question(I remember we had some discussion like this but I
forget the conclusion):
Sorry, I forgot to update you.
I see e.g in vringh_getdesc_kern() it has the following comment:
/*
* Note that you may need to clean up riov and wiov, even on error!
*/
So it looks to me the correct way is to call vringh_kiov_cleanup()
before?
Looking at the code the right pattern should be:
vringh_getdesc_*(..., &out_iov, &in_iov, ...);
// use out_iov and in_iov
vringh_kiov_cleanup(&out_iov);
vringh_kiov_cleanup(&in_iov);
This because vringh_getdesc_*() calls __vringh_iov() where
resize_iovec() is called to allocate the iov wrapped by 'struct
vringh_kiov' and vringh_kiov_cleanup() frees that memory.
Looking better, __vringh_iov() is able to extend a 'vringh_kiov'
pre-allocated, so in order to avoid to allocate and free the iov for
each request we can avoid to call vringh_kiov_cleanup(), but this patch
is needed to avoid an inconsistent state.
And also patch "vdpa_sim: cleanup kiovs in vdpasim_free()" is required
to free the iov when the device is going away.
Does that make sense to you?
Maybe I should add a comment in vringh.c to explain this better.
Thanks,
Stefano
Thanks
---
drivers/vhost/vringh.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c
index f68122705719..bee63d68201a 100644
--- a/drivers/vhost/vringh.c
+++ b/drivers/vhost/vringh.c
@@ -290,9 +290,9 @@ __vringh_iov(struct vringh *vrh, u16 i,
return -EINVAL;
if (riov)
- riov->i = riov->used = 0;
+ riov->i = riov->used = riov->consumed = 0;
if (wiov)
- wiov->i = wiov->used = 0;
+ wiov->i = wiov->used = wiov->consumed = 0;
for (;;) {
void *addr;
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