56 lines
2.3 KiB
Diff
56 lines
2.3 KiB
Diff
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From: "Michael S. Tsirkin" <mst@redhat.com>
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Date: Tue, 15 Feb 2011 18:27:52 +0200
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Subject: e1000: clear EOP for multi-buffer descriptors
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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Patch-mainline: v0.15.0-rc0
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Git-commit: ee912ccfa007351a62ba42bd60499769f6c02c1e
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References: bnc#840196
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The e1000 spec says: if software statically allocates
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buffers, and uses memory read to check for completed descriptors, it
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simply has to zero the status byte in the descriptor to make it ready
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for reuse by hardware. This is not a hardware requirement (moving the
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hardware tail pointer is), but is necessary for performing an in–memory
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scan.
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Thus the guest does not have to clear the status byte. In case it
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doesn't we need to clear EOP for all descriptors
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except the last. While I don't know of any such guests,
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it's probably a good idea to stick to the spec.
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Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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Reported-by: Juan Quintela <quintela@redhat.com>
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Acked-by: Alex Williamson <alex.williamson@redhat.com>
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Acked-by: Kevin Wolf <kwolf@redhat.com>
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Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
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Acked-by: Michal Kubecek <mkubecek@suse.cz>
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---
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tools/qemu-xen-traditional-dir-remote/hw/e1000.c | 6 ++++--
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1 file changed, 4 insertions(+), 2 deletions(-)
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diff --git a/tools/qemu-xen-traditional-dir-remote/hw/e1000.c b/tools/qemu-xen-traditional-dir-remote/hw/e1000.c
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index 34818e0..7e791dc 100644
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--- a/tools/qemu-xen-traditional-dir-remote/hw/e1000.c
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+++ b/tools/qemu-xen-traditional-dir-remote/hw/e1000.c
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@@ -694,11 +694,13 @@ e1000_receive(void *opaque, const uint8_t *buf, int size)
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copy_size);
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}
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desc_offset += desc_size;
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+ desc.length = cpu_to_le16(desc_size);
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if (desc_offset >= total_size) {
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- desc.length = cpu_to_le16(desc_size);
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desc.status |= E1000_RXD_STAT_EOP | E1000_RXD_STAT_IXSM;
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} else {
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- desc.length = cpu_to_le16(desc_size);
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+ /* Guest zeroing out status is not a hardware requirement.
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+ Clear EOP in case guest didn't do it. */
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+ desc.status &= ~E1000_RXD_STAT_EOP;
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}
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} else // as per intel docs; skip descriptors with null buf addr
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DBGOUT(RX, "Null RX descriptor!!\n");
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--
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1.8.1.4
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