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e1000: verify we have buffers, upfront

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The spec says: Any descriptor with a non-zero status byte has been
processed by the hardware, and is ready to be handled by the software.

Thus, once we change a descriptor status to non-zero we should
never move the head backwards and try to reuse this
descriptor from hardware.

This actually happened with a multibuffer packet
that arrives when we don't have enough buffers.

Fix by checking that we have enough buffers upfront
so we never need to discard the packet midway through.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Alex Williamson <alex.williamson@redhat.com>
Acked-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
This commit is contained in:
Michael S. Tsirkin 2011-02-15 18:27:55 +02:00 committed by Aurelien Jarno
parent ee912ccfa0
commit 322fd48afb
1 changed files with 22 additions and 6 deletions
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28
hw/e1000.c
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@ -631,6 +631,24 @@ e1000_can_receive(VLANClientState *nc)
return (s->mac_reg[RCTL] & E1000_RCTL_EN);
}
static bool e1000_has_rxbufs(E1000State *s, size_t total_size)
{
int bufs;
/* Fast-path short packets */
if (total_size <= s->rxbuf_size) {
return s->mac_reg[RDH] != s->mac_reg[RDT] || !s->check_rxov;
}
if (s->mac_reg[RDH] < s->mac_reg[RDT]) {
bufs = s->mac_reg[RDT] - s->mac_reg[RDH];
} else if (s->mac_reg[RDH] > s->mac_reg[RDT] || !s->check_rxov) {
bufs = s->mac_reg[RDLEN] / sizeof(struct e1000_rx_desc) +
s->mac_reg[RDT] - s->mac_reg[RDH];
} else {
return false;
}
return total_size <= bufs * s->rxbuf_size;
}
static ssize_t
e1000_receive(VLANClientState *nc, const uint8_t *buf, size_t size)
{
@ -671,17 +689,15 @@ e1000_receive(VLANClientState *nc, const uint8_t *buf, size_t size)
rdh_start = s->mac_reg[RDH];
desc_offset = 0;
total_size = size + fcs_len(s);
if (!e1000_has_rxbufs(s, total_size)) {
set_ics(s, 0, E1000_ICS_RXO);
return -1;
}
do {
desc_size = total_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;
}
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));