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Re: [Qemu-devel] [PATCHv2] e1000: multi-buffer packet support
From: |
Kevin Wolf |
Subject: |
Re: [Qemu-devel] [PATCHv2] e1000: multi-buffer packet support |
Date: |
Tue, 08 Feb 2011 15:07:58 +0100 |
User-agent: |
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.15) Gecko/20101027 Fedora/3.0.10-1.fc12 Thunderbird/3.0.10 |
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