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Diffstat (limited to 'results/classifier/deepseek-2-tmp/output/network/1402755')
| -rw-r--r-- | results/classifier/deepseek-2-tmp/output/network/1402755 | 64 |
1 files changed, 64 insertions, 0 deletions
diff --git a/results/classifier/deepseek-2-tmp/output/network/1402755 b/results/classifier/deepseek-2-tmp/output/network/1402755 new file mode 100644 index 000000000..52201bafb --- /dev/null +++ b/results/classifier/deepseek-2-tmp/output/network/1402755 @@ -0,0 +1,64 @@ + +qemu-kvm: e1000 RX ring is filled with partial-pkt of size 0 + +Hello, +We are using CentOS 6.5 with qemu-kvm-0.12.1.2-2.415 as a host of or VMs. +In the VM we use e1000 as the NIC emulation. +We've modified the e1000 driver to our needs. This modification start the RX engine while the RX ring is empty (RDH == RDT) +and at a later stage we fill the RX descriptors with buffers. This scheme works well on intel chips and VMware. +What we observe in this setup is that from time to time the RX ring is filled with "partial packets" of size 0 (meaning, DD bit is set, +No other status bits are set and packet size is also 0). + +Looking at the e1000 RX routine in qemu-kvm you can observe the following flow: +1. A packet is avail for receive: +2. The routine checks for RCTL_EN - it is enabled +3. The routine checks that the RDH equal RDT (they are as the ring is empty) but also checks if rxov is on (it is still off) so it doesn’t +Exit as it is supposed to. +4. The routine now updates the descriptor status with the DD bit (and vlan which we don’t care) +5. The routine checks if a buffer address is not NULL (it is as NULL since we haven’t filled it yet) – so is logs something. +6. The routine now updates the guest memory with this value (DD is 1) +7. The routine updates the check_rxov flag in order to allow ovf check the next time around. +(but ovf will not occur since in the next iteration RDH != RDT) +8. The routine loops over all the descriptors with the NULL buffer (which is all our ring) and writes the DD bit +9. We get this endless partial packet problem we see. + +qemu-kvm-0.12.1.2-2.415.el6_5.3/qemu-kvm-0.12.1.2/hw/e1000.c +static ssize_t +e1000_receive(VLANClientState *nc, const uint8_t *buf, size_t size) +{ +: : : +if (!(s->mac_reg[RCTL] & E1000_RCTL_EN)) +return -1; + +: : : +do { +if (s->mac_reg[RDH] == s->mac_reg[RDT] && s->check_rxov) { +set_ics(s, 0, E1000_ICS_RXO); +return -1; +} +base = ((uint64_t)s->mac_reg[RDBAH] << 32) + s->mac_reg[RDBAL] + +sizeof(desc) * s->mac_reg[RDH]; +cpu_physical_memory_read(base, (void *)&desc, sizeof(desc)); +desc.special = vlan_special; +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); +desc.status |= E1000_RXD_STAT_EOP|E1000_RXD_STAT_IXSM; +} else // as per intel docs; skip descriptors with null buf addr +DBGOUT(RX, "Null RX descriptor!!\n"); +cpu_physical_memory_write(base, (void *)&desc, sizeof(desc)); + +: : : +if (++s->mac_reg[RDH] * sizeof(desc) >= s->mac_reg[RDLEN]) +s->mac_reg[RDH] = 0; +s->check_rxov = 1; +: : : +} while (desc.buffer_addr == 0); +} + + +A workaround is to enable the RX machine only after the descriptor ring is filled for the first time. + +Moti \ No newline at end of file |