| Message ID | 20210128144127.113245-4-sgarzare@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | vdpa: add vdpa simulator for block device | expand |
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@redhat.com> I had a question(I remember we had some discussion like this but I forget the conclusion): 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? 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;
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@redhat.com> > > >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; >
On 2021/2/1 下午6:21, Stefano Garzarella wrote: > 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@redhat.com> >> >> >> 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? Make sense. > > Maybe I should add a comment in vringh.c to explain this better. Yes, please. Thanks > > 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; >> >
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;
__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@redhat.com> --- drivers/vhost/vringh.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)