From 2ca434e82872a7502aac89c99636808e2cb5dbb8 Mon Sep 17 00:00:00 2001 From: Michael S. Tsirkin Date: Thu, 17 Feb 2011 09:01:59 -0200 Subject: [PATCH 1/4] e1000: clear EOP for multi-buffer descriptors MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit RH-Author: Michael S. Tsirkin Message-id: <0cd0846170b6823fba9d13cc2de50d69ae7d38e8.1297933168.git.mst@redhat.com> Patchwork-id: 18371 O-Subject: [PATCH RHEL6.1 1/2] e1000: clear EOP for multi-buffer descriptors Bugzilla: 678338 RH-Acked-by: Alex Williamson RH-Acked-by: Kevin Wolf RH-Acked-by: Jes Sorensen The e1000 spec says: if software statically allocates buffers, and uses memory read to check for completed descriptors, it simply has to zero the status byte in the descriptor to make it ready for reuse by hardware. This is not a hardware requirement (moving the hardware tail pointer is), but is necessary for performing an in–memory scan. Thus the guest does not have to clear the status byte. In case it doesn't we need to clear EOP for all descriptors except the last. While I don't know of any such guests, it's probably a good idea to stick to the spec. Signed-off-by: Michael S. Tsirkin Reported-by: Juan Quintela Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=602205 Upstream: posted --- hw/e1000.c | 6 ++++-- 1 files changed, 4 insertions(+), 2 deletions(-) Signed-off-by: Luiz Capitulino --- hw/e1000.c | 6 ++++-- 1 files changed, 4 insertions(+), 2 deletions(-) diff --git a/hw/e1000.c b/hw/e1000.c index bce0195..e4ed0a0 100644 --- a/hw/e1000.c +++ b/hw/e1000.c @@ -678,11 +678,13 @@ e1000_receive(VLANClientState *nc, const uint8_t *buf, size_t size) (void *)(buf + desc_offset + vlan_offset), desc_size); desc_offset += desc_size; + desc.length = cpu_to_le16(desc_size); if (desc_offset >= size) { - desc.length = cpu_to_le16(desc_size); desc.status |= E1000_RXD_STAT_EOP | E1000_RXD_STAT_IXSM; } else { - desc.length = cpu_to_le16(desc_size); + /* Guest zeroing out status is not a hardware requirement. + Clear EOP in case guest didn't do it. */ + desc.status &= ~E1000_RXD_STAT_EOP; } } else // as per intel docs; skip descriptors with null buf addr DBGOUT(RX, "Null RX descriptor!!\n"); -- 1.7.4.rc1.16.gd2f15e