| Message ID | 1426239723-25789-1-git-send-email-aik@ozlabs.ru (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
Alexey Kardashevskiy <aik@ozlabs.ru> writes: > The value returned by virtio_vring_size() is used to allocate memory > for vring. The used descriptor list (array of vring_used_elem) is > counted by the header - vring_used struct - is not. > > This fixes virtio_vring_size() to return the correct size. > At the moment rings are quite small (256) and allocated with > 4096 alignment, this is why we have not been having issues with > this so far. > > Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> Reviewed-by: Nikunj A Dadhania <nikunj@linux.vnet.ibm.com> > --- > Changes: > v2: > * remove magic numbers > --- > lib/libvirtio/virtio.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/lib/libvirtio/virtio.c b/lib/libvirtio/virtio.c > index b010796..f9c00a6 100644 > --- a/lib/libvirtio/virtio.c > +++ b/lib/libvirtio/virtio.c > @@ -32,8 +32,10 @@ > */ > unsigned long virtio_vring_size(unsigned int qsize) > { > - return VQ_ALIGN(sizeof(struct vring_desc) * qsize + 2 * (2 + qsize)) > - + VQ_ALIGN(sizeof(struct vring_used_elem) * qsize); > + return VQ_ALIGN(sizeof(struct vring_desc) * qsize + > + sizeof(struct vring_avail) + sizeof(uint16_t) * qsize) + > + VQ_ALIGN(sizeof(struct vring_used) + > + sizeof(struct vring_used_elem) * qsize); > } > > > -- > 2.0.0
On Fri, 13 Mar 2015 20:42:03 +1100 Alexey Kardashevskiy <aik@ozlabs.ru> wrote: > The value returned by virtio_vring_size() is used to allocate memory > for vring. The used descriptor list (array of vring_used_elem) is > counted by the header - vring_used struct - is not. > > This fixes virtio_vring_size() to return the correct size. > At the moment rings are quite small (256) and allocated with > 4096 alignment, this is why we have not been having issues with > this so far. > > Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> > --- > Changes: > v2: > * remove magic numbers > --- > lib/libvirtio/virtio.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/lib/libvirtio/virtio.c b/lib/libvirtio/virtio.c > index b010796..f9c00a6 100644 > --- a/lib/libvirtio/virtio.c > +++ b/lib/libvirtio/virtio.c > @@ -32,8 +32,10 @@ > */ > unsigned long virtio_vring_size(unsigned int qsize) > { > - return VQ_ALIGN(sizeof(struct vring_desc) * qsize + 2 * (2 + qsize)) > - + VQ_ALIGN(sizeof(struct vring_used_elem) * qsize); > + return VQ_ALIGN(sizeof(struct vring_desc) * qsize + > + sizeof(struct vring_avail) + sizeof(uint16_t) * qsize) + > + VQ_ALIGN(sizeof(struct vring_used) + > + sizeof(struct vring_used_elem) * qsize); > } Reviewed-by: Thomas Huth <thuth@linux.vnet.ibm.com> That should be at least ok for the current status that we support in SLOF. I think I might have written the original version of that function with a very old version of the virtio spec (v0.8.10), when ther was no "used_event" event field in the struct vring_avail defined yet. But if SLOF ever supports VIRTIO_F_EVENT_IDX, we've got to keep in mind to add some additional bytes here, too. Thomas
diff --git a/lib/libvirtio/virtio.c b/lib/libvirtio/virtio.c index b010796..f9c00a6 100644 --- a/lib/libvirtio/virtio.c +++ b/lib/libvirtio/virtio.c @@ -32,8 +32,10 @@ */ unsigned long virtio_vring_size(unsigned int qsize) { - return VQ_ALIGN(sizeof(struct vring_desc) * qsize + 2 * (2 + qsize)) - + VQ_ALIGN(sizeof(struct vring_used_elem) * qsize); + return VQ_ALIGN(sizeof(struct vring_desc) * qsize + + sizeof(struct vring_avail) + sizeof(uint16_t) * qsize) + + VQ_ALIGN(sizeof(struct vring_used) + + sizeof(struct vring_used_elem) * qsize); }
The value returned by virtio_vring_size() is used to allocate memory for vring. The used descriptor list (array of vring_used_elem) is counted by the header - vring_used struct - is not. This fixes virtio_vring_size() to return the correct size. At the moment rings are quite small (256) and allocated with 4096 alignment, this is why we have not been having issues with this so far. Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> --- Changes: v2: * remove magic numbers --- lib/libvirtio/virtio.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)