From 04fce2d4989b18d27d6dd02f6b5d21e1cae155b1 Mon Sep 17 00:00:00 2001 From: "Michael S. Tsirkin" Date: Tue, 15 Feb 2011 18:27:52 +0200 Subject: [PATCH] e1000: clear EOP for multi-buffer descriptors MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 Acked-by: Alex Williamson Acked-by: Kevin Wolf Signed-off-by: Aurelien Jarno --- hw/e1000.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/hw/e1000.c b/hw/e1000.c index 050ce02..2943a1a 100644 --- a/hw/e1000.c +++ b/hw/e1000.c @@ -698,11 +698,13 @@ e1000_receive(VLANClientState *nc, const uint8_t *buf, size_t size) copy_size); } desc_offset += desc_size; + desc.length = cpu_to_le16(desc_size); if (desc_offset >= total_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"); -- 2.7.4