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Re: [Qemu-devel] [PATCHv2] e1000: multi-buffer packet support
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCHv2] e1000: multi-buffer packet support |
Date: |
Tue, 8 Feb 2011 18:02:56 +0200 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Tue, Feb 08, 2011 at 03:07:58PM +0100, Kevin Wolf wrote:
> Am 03.02.2011 17:49, schrieb Michael S. Tsirkin:
> > e1000 supports multi-buffer packets larger than rxbuf_size.
> >
> > This fixes the following (on linux):
> > - in guest: ifconfig eth1 mtu 16110
> > - in host: ifconfig tap0 mtu 16110
> > ping -s 16082 <guest-ip>
> >
> > Red Hat bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=602205
> >
> > Signed-off-by: Michael S. Tsirkin <address@hidden>
> > ---
> >
> > Changes from v1:
> > removed dead code
> >
> > hw/e1000.c | 29 +++++++++++++++++++----------
> > 1 files changed, 19 insertions(+), 10 deletions(-)
> >
> > diff --git a/hw/e1000.c b/hw/e1000.c
> > index af101bd..3427ff3 100644
> > --- a/hw/e1000.c
> > +++ b/hw/e1000.c
> > @@ -642,6 +642,8 @@ e1000_receive(VLANClientState *nc, const uint8_t *buf,
> > size_t size)
> > uint16_t vlan_special = 0;
> > uint8_t vlan_status = 0, vlan_offset = 0;
> > uint8_t min_buf[MIN_BUF_SIZE];
> > + size_t desc_offset;
> > + size_t desc_size;
> >
> > if (!(s->mac_reg[RCTL] & E1000_RCTL_EN))
> > return -1;
> > @@ -654,12 +656,6 @@ e1000_receive(VLANClientState *nc, const uint8_t *buf,
> > size_t size)
> > size = sizeof(min_buf);
> > }
> >
> > - if (size > s->rxbuf_size) {
> > - DBGOUT(RX, "packet too large for buffers (%lu > %d)\n",
> > - (unsigned long)size, s->rxbuf_size);
> > - return -1;
> > - }
> > -
> > if (!receive_filter(s, buf, size))
> > return size;
> >
> > @@ -672,8 +668,15 @@ e1000_receive(VLANClientState *nc, const uint8_t *buf,
> > size_t size)
> > }
> >
> > rdh_start = s->mac_reg[RDH];
> > + desc_offset = 0;
> > do {
> > + desc_size = size - desc_offset;
> > + if (desc_size > s->rxbuf_size) {
> > + desc_size = s->rxbuf_size;
> > + }
> > if (s->mac_reg[RDH] == s->mac_reg[RDT] && s->check_rxov) {
> > + /* Discard all data written so far */
> > + s->mac_reg[RDH] = rdh_start;
> > set_ics(s, 0, E1000_ICS_RXO);
> > return -1;
> > }
> > @@ -684,9 +687,15 @@ e1000_receive(VLANClientState *nc, const uint8_t *buf,
> > size_t size)
> > desc.status |= (vlan_status | E1000_RXD_STAT_DD);
> > if (desc.buffer_addr) {
> > cpu_physical_memory_write(le64_to_cpu(desc.buffer_addr),
> > - (void *)(buf + vlan_offset), size);
> > - desc.length = cpu_to_le16(size + fcs_len(s));
> > - desc.status |= E1000_RXD_STAT_EOP|E1000_RXD_STAT_IXSM;
> > + (void *)(buf + desc_offset +
> > vlan_offset),
> > + desc_size);
> > + desc_offset += desc_size;
> > + if (desc_offset >= size) {
> > + desc.length = cpu_to_le16(desc_size + fcs_len(s));
>
> I think this is not quite right: What happens if desc_size + fcs_len(s)
> > s->rxbuf_size? IIUC, we would seemingly overflow the guests buffer (in
> reality we leave the extra bytes untouched, but we may confuse the guest).
>
> Kevin
Hmm, good point.