| Message ID | 04d3e68d5be34a87514a33fcd789339748d43cb5.1348527749.git.mst@redhat.com |
|---|---|
| State | New |
| Headers | show |
"Michael S. Tsirkin" <mst@redhat.com> writes: > Avoid tweaking iovec during receive. This removes > the need to copy the vector. > Note: we already have an evil cast in work_around_broken_dhclient > and unfortunately this adds another one. > const on buf is ignored by this function anyway so arguably > this is not making things much worse. > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com> > --- > hw/virtio-net.c | 45 +++++++++++++++++++++------------------------ > iov.h | 8 ++++---- > 2 files changed, 25 insertions(+), 28 deletions(-) > > diff --git a/hw/virtio-net.c b/hw/virtio-net.c > index 0c5081e..6e53858 100644 > --- a/hw/virtio-net.c > +++ b/hw/virtio-net.c > @@ -503,7 +503,7 @@ static int virtio_net_has_buffers(VirtIONet *n, int bufsize) > * we should provide a mechanism to disable it to avoid polluting the host > * cache. > */ > -static void work_around_broken_dhclient(struct virtio_net_hdr *hdr, > +static void work_around_broken_dhclient(const struct virtio_net_hdr *hdr, > const uint8_t *buf, size_t size) > { > if ((hdr->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) && /* missing csum */ > @@ -513,31 +513,27 @@ static void work_around_broken_dhclient(struct virtio_net_hdr *hdr, > (buf[34] == 0 && buf[35] == 67)) { /* udp.srcport == bootps */ > /* FIXME this cast is evil */ > net_checksum_calculate((uint8_t *)buf, size); > - hdr->flags &= ~VIRTIO_NET_HDR_F_NEEDS_CSUM; > + ((struct virtio_net_hdr *)hdr)->flags &= > ~VIRTIO_NET_HDR_F_NEEDS_CSUM; > } > } > > -static int receive_header(VirtIONet *n, struct iovec *iov, int iovcnt, > - const void *buf, size_t size, size_t hdr_len) > +static int receive_header(VirtIONet *n, const struct iovec *iov, int iov_cnt, > + const void *buf, size_t size) > { > - struct virtio_net_hdr *hdr = (struct virtio_net_hdr *)iov[0].iov_base; > int offset = 0; > > - hdr->flags = 0; > - hdr->gso_type = VIRTIO_NET_HDR_GSO_NONE; > - > if (n->has_vnet_hdr) { > - memcpy(hdr, buf, sizeof(*hdr)); > - offset = sizeof(*hdr); > - work_around_broken_dhclient(hdr, buf + offset, size - offset); > + work_around_broken_dhclient(buf, buf + offset, size - > offset); I think it would be less ugly to cast here. > + offset = sizeof(struct virtio_net_hdr); > + iov_from_buf(iov, iov_cnt, 0, buf, offset); > + } else { > + struct virtio_net_hdr hdr = { > + .flags = 0, > + .gso_type = VIRTIO_NET_HDR_GSO_NONE > + }; > + iov_from_buf(iov, iov_cnt, 0, &hdr, sizeof hdr); > } > > - /* We only ever receive a struct virtio_net_hdr from the tapfd, > - * but we may be passing along a larger header to the guest. > - */ > - iov[0].iov_base += hdr_len; > - iov[0].iov_len -= hdr_len; > - > return offset; > } > > @@ -598,7 +594,8 @@ static ssize_t virtio_net_receive(NetClientState *nc, const uint8_t *buf, size_t > { > VirtIONet *n = DO_UPCAST(NICState, nc, nc)->opaque; > struct virtio_net_hdr_mrg_rxbuf *mhdr = NULL; > - size_t offset, i; > + const struct iovec *sg = elem.in_sg; > + size_t offset, i, guest_offset; > > if (!virtio_net_can_receive(&n->nic->nc)) > return -1; > @@ -615,7 +612,7 @@ static ssize_t virtio_net_receive(NetClientState *nc, const uint8_t *buf, size_t > while (offset < size) { > VirtQueueElement elem; > int len, total; > - struct iovec sg[VIRTQUEUE_MAX_SIZE]; > + const struct iovec *sg = elem.in_sg; > > total = 0; > > @@ -640,20 +637,20 @@ static ssize_t virtio_net_receive(NetClientState *nc, const uint8_t *buf, size_t > exit(1); > } > > - memcpy(&sg, &elem.in_sg[0], sizeof(sg[0]) * elem.in_num); > - > if (i == 0) { > if (n->mergeable_rx_bufs) > mhdr = (struct virtio_net_hdr_mrg_rxbuf *)sg[0].iov_base; > > offset += receive_header(n, sg, elem.in_num, > - buf + offset, size - offset, > - n->guest_hdr_len); > + buf + offset, size - offset); > total += n->guest_hdr_len; > + guest_offset = n->guest_hdr_len; > + } else { > + guest_offset = 0; > } > > /* copy in packet. ugh */ > - len = iov_from_buf(sg, elem.in_num, 0, > + len = iov_from_buf(sg, elem.in_num, guest_offset, > buf + offset, size - offset); > total += len; > offset += len; > diff --git a/iov.h b/iov.h > index f0daefa..6c9fdf1 100644 > --- a/iov.h > +++ b/iov.h > @@ -90,8 +90,8 @@ void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt, > /* > * Partial copy of vector from iov to dst_iov (data is not copied). > * dst_iov overlaps iov at a specified offset. > - * size of dst_iov is at most bytes. Actual size is returned. > + * size of dst_iov is at most bytes. dst vector count is returned. > */ > -size_t iov_cpy(struct iovec *dst_iov, unsigned int dst_iov_cnt, > - const struct iovec *iov, unsigned int iov_cnt, > - size_t offset, size_t bytes); > +unsigned iov_cpy(struct iovec *dst_iov, unsigned int dst_iov_cnt, > + const struct iovec *iov, unsigned int iov_cnt, > + size_t offset, size_t bytes); I think this belongs in an earlier patch. Regards, Anthony Liguori > -- > MST
On Mon, Sep 24, 2012 at 07:37:40PM -0500, Anthony Liguori wrote: > "Michael S. Tsirkin" <mst@redhat.com> writes: > > > Avoid tweaking iovec during receive. This removes > > the need to copy the vector. > > Note: we already have an evil cast in work_around_broken_dhclient > > and unfortunately this adds another one. > > const on buf is ignored by this function anyway so arguably > > this is not making things much worse. > > > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com> > > --- > > hw/virtio-net.c | 45 +++++++++++++++++++++------------------------ > > iov.h | 8 ++++---- > > 2 files changed, 25 insertions(+), 28 deletions(-) > > > > diff --git a/hw/virtio-net.c b/hw/virtio-net.c > > index 0c5081e..6e53858 100644 > > --- a/hw/virtio-net.c > > +++ b/hw/virtio-net.c > > @@ -503,7 +503,7 @@ static int virtio_net_has_buffers(VirtIONet *n, int bufsize) > > * we should provide a mechanism to disable it to avoid polluting the host > > * cache. > > */ > > -static void work_around_broken_dhclient(struct virtio_net_hdr *hdr, > > +static void work_around_broken_dhclient(const struct virtio_net_hdr *hdr, > > const uint8_t *buf, size_t size) > > { > > if ((hdr->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) && /* missing csum */ > > @@ -513,31 +513,27 @@ static void work_around_broken_dhclient(struct virtio_net_hdr *hdr, > > (buf[34] == 0 && buf[35] == 67)) { /* udp.srcport == bootps */ > > /* FIXME this cast is evil */ > > net_checksum_calculate((uint8_t *)buf, size); > > - hdr->flags &= ~VIRTIO_NET_HDR_F_NEEDS_CSUM; > > + ((struct virtio_net_hdr *)hdr)->flags &= > > ~VIRTIO_NET_HDR_F_NEEDS_CSUM; > > } > > } > > > > -static int receive_header(VirtIONet *n, struct iovec *iov, int iovcnt, > > - const void *buf, size_t size, size_t hdr_len) > > +static int receive_header(VirtIONet *n, const struct iovec *iov, int iov_cnt, > > + const void *buf, size_t size) > > { > > - struct virtio_net_hdr *hdr = (struct virtio_net_hdr *)iov[0].iov_base; > > int offset = 0; > > > > - hdr->flags = 0; > > - hdr->gso_type = VIRTIO_NET_HDR_GSO_NONE; > > - > > if (n->has_vnet_hdr) { > > - memcpy(hdr, buf, sizeof(*hdr)); > > - offset = sizeof(*hdr); > > - work_around_broken_dhclient(hdr, buf + offset, size - offset); > > + work_around_broken_dhclient(buf, buf + offset, size - > > offset); > > I think it would be less ugly to cast here. I was thinking about this but could not decide either way. Will do. > > + offset = sizeof(struct virtio_net_hdr); > > + iov_from_buf(iov, iov_cnt, 0, buf, offset); > > + } else { > > + struct virtio_net_hdr hdr = { > > + .flags = 0, > > + .gso_type = VIRTIO_NET_HDR_GSO_NONE > > + }; > > + iov_from_buf(iov, iov_cnt, 0, &hdr, sizeof hdr); > > } > > > > - /* We only ever receive a struct virtio_net_hdr from the tapfd, > > - * but we may be passing along a larger header to the guest. > > - */ > > - iov[0].iov_base += hdr_len; > > - iov[0].iov_len -= hdr_len; > > - > > return offset; > > } > > > > @@ -598,7 +594,8 @@ static ssize_t virtio_net_receive(NetClientState *nc, const uint8_t *buf, size_t > > { > > VirtIONet *n = DO_UPCAST(NICState, nc, nc)->opaque; > > struct virtio_net_hdr_mrg_rxbuf *mhdr = NULL; > > - size_t offset, i; > > + const struct iovec *sg = elem.in_sg; > > + size_t offset, i, guest_offset; > > > > if (!virtio_net_can_receive(&n->nic->nc)) > > return -1; > > @@ -615,7 +612,7 @@ static ssize_t virtio_net_receive(NetClientState *nc, const uint8_t *buf, size_t > > while (offset < size) { > > VirtQueueElement elem; > > int len, total; > > - struct iovec sg[VIRTQUEUE_MAX_SIZE]; > > + const struct iovec *sg = elem.in_sg; > > > > total = 0; > > > > @@ -640,20 +637,20 @@ static ssize_t virtio_net_receive(NetClientState *nc, const uint8_t *buf, size_t > > exit(1); > > } > > > > - memcpy(&sg, &elem.in_sg[0], sizeof(sg[0]) * elem.in_num); > > - > > if (i == 0) { > > if (n->mergeable_rx_bufs) > > mhdr = (struct virtio_net_hdr_mrg_rxbuf *)sg[0].iov_base; > > > > offset += receive_header(n, sg, elem.in_num, > > - buf + offset, size - offset, > > - n->guest_hdr_len); > > + buf + offset, size - offset); > > total += n->guest_hdr_len; > > + guest_offset = n->guest_hdr_len; > > + } else { > > + guest_offset = 0; > > } > > > > /* copy in packet. ugh */ > > - len = iov_from_buf(sg, elem.in_num, 0, > > + len = iov_from_buf(sg, elem.in_num, guest_offset, > > buf + offset, size - offset); > > total += len; > > offset += len; > > diff --git a/iov.h b/iov.h > > index f0daefa..6c9fdf1 100644 > > --- a/iov.h > > +++ b/iov.h > > @@ -90,8 +90,8 @@ void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt, > > /* > > * Partial copy of vector from iov to dst_iov (data is not copied). > > * dst_iov overlaps iov at a specified offset. > > - * size of dst_iov is at most bytes. Actual size is returned. > > + * size of dst_iov is at most bytes. dst vector count is returned. > > */ > > -size_t iov_cpy(struct iovec *dst_iov, unsigned int dst_iov_cnt, > > - const struct iovec *iov, unsigned int iov_cnt, > > - size_t offset, size_t bytes); > > +unsigned iov_cpy(struct iovec *dst_iov, unsigned int dst_iov_cnt, > > + const struct iovec *iov, unsigned int iov_cnt, > > + size_t offset, size_t bytes); > > I think this belongs in an earlier patch. Good catch thanks. > Regards, > > Anthony Liguori > > > -- > > MST
diff --git a/hw/virtio-net.c b/hw/virtio-net.c index 0c5081e..6e53858 100644 --- a/hw/virtio-net.c +++ b/hw/virtio-net.c @@ -503,7 +503,7 @@ static int virtio_net_has_buffers(VirtIONet *n, int bufsize) * we should provide a mechanism to disable it to avoid polluting the host * cache. */ -static void work_around_broken_dhclient(struct virtio_net_hdr *hdr, +static void work_around_broken_dhclient(const struct virtio_net_hdr *hdr, const uint8_t *buf, size_t size) { if ((hdr->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) && /* missing csum */ @@ -513,31 +513,27 @@ static void work_around_broken_dhclient(struct virtio_net_hdr *hdr, (buf[34] == 0 && buf[35] == 67)) { /* udp.srcport == bootps */ /* FIXME this cast is evil */ net_checksum_calculate((uint8_t *)buf, size); - hdr->flags &= ~VIRTIO_NET_HDR_F_NEEDS_CSUM; + ((struct virtio_net_hdr *)hdr)->flags &= ~VIRTIO_NET_HDR_F_NEEDS_CSUM; } } -static int receive_header(VirtIONet *n, struct iovec *iov, int iovcnt, - const void *buf, size_t size, size_t hdr_len) +static int receive_header(VirtIONet *n, const struct iovec *iov, int iov_cnt, + const void *buf, size_t size) { - struct virtio_net_hdr *hdr = (struct virtio_net_hdr *)iov[0].iov_base; int offset = 0; - hdr->flags = 0; - hdr->gso_type = VIRTIO_NET_HDR_GSO_NONE; - if (n->has_vnet_hdr) { - memcpy(hdr, buf, sizeof(*hdr)); - offset = sizeof(*hdr); - work_around_broken_dhclient(hdr, buf + offset, size - offset); + work_around_broken_dhclient(buf, buf + offset, size - offset); + offset = sizeof(struct virtio_net_hdr); + iov_from_buf(iov, iov_cnt, 0, buf, offset); + } else { + struct virtio_net_hdr hdr = { + .flags = 0, + .gso_type = VIRTIO_NET_HDR_GSO_NONE + }; + iov_from_buf(iov, iov_cnt, 0, &hdr, sizeof hdr); } - /* We only ever receive a struct virtio_net_hdr from the tapfd, - * but we may be passing along a larger header to the guest. - */ - iov[0].iov_base += hdr_len; - iov[0].iov_len -= hdr_len; - return offset; } @@ -598,7 +594,8 @@ static ssize_t virtio_net_receive(NetClientState *nc, const uint8_t *buf, size_t { VirtIONet *n = DO_UPCAST(NICState, nc, nc)->opaque; struct virtio_net_hdr_mrg_rxbuf *mhdr = NULL; - size_t offset, i; + const struct iovec *sg = elem.in_sg; + size_t offset, i, guest_offset; if (!virtio_net_can_receive(&n->nic->nc)) return -1; @@ -615,7 +612,7 @@ static ssize_t virtio_net_receive(NetClientState *nc, const uint8_t *buf, size_t while (offset < size) { VirtQueueElement elem; int len, total; - struct iovec sg[VIRTQUEUE_MAX_SIZE]; + const struct iovec *sg = elem.in_sg; total = 0; @@ -640,20 +637,20 @@ static ssize_t virtio_net_receive(NetClientState *nc, const uint8_t *buf, size_t exit(1); } - memcpy(&sg, &elem.in_sg[0], sizeof(sg[0]) * elem.in_num); - if (i == 0) { if (n->mergeable_rx_bufs) mhdr = (struct virtio_net_hdr_mrg_rxbuf *)sg[0].iov_base; offset += receive_header(n, sg, elem.in_num, - buf + offset, size - offset, - n->guest_hdr_len); + buf + offset, size - offset); total += n->guest_hdr_len; + guest_offset = n->guest_hdr_len; + } else { + guest_offset = 0; } /* copy in packet. ugh */ - len = iov_from_buf(sg, elem.in_num, 0, + len = iov_from_buf(sg, elem.in_num, guest_offset, buf + offset, size - offset); total += len; offset += len; diff --git a/iov.h b/iov.h index f0daefa..6c9fdf1 100644 --- a/iov.h +++ b/iov.h @@ -90,8 +90,8 @@ void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt, /* * Partial copy of vector from iov to dst_iov (data is not copied). * dst_iov overlaps iov at a specified offset. - * size of dst_iov is at most bytes. Actual size is returned. + * size of dst_iov is at most bytes. dst vector count is returned. */ -size_t iov_cpy(struct iovec *dst_iov, unsigned int dst_iov_cnt, - const struct iovec *iov, unsigned int iov_cnt, - size_t offset, size_t bytes); +unsigned iov_cpy(struct iovec *dst_iov, unsigned int dst_iov_cnt, + const struct iovec *iov, unsigned int iov_cnt, + size_t offset, size_t bytes);
Avoid tweaking iovec during receive. This removes the need to copy the vector. Note: we already have an evil cast in work_around_broken_dhclient and unfortunately this adds another one. const on buf is ignored by this function anyway so arguably this is not making things much worse. Signed-off-by: Michael S. Tsirkin <mst@redhat.com> --- hw/virtio-net.c | 45 +++++++++++++++++++++------------------------ iov.h | 8 ++++---- 2 files changed, 25 insertions(+), 28 deletions(-)