From: Olivier Matz <olivier.matz@6wind.com>
To: dev@dpdk.org, yuanhan.liu@linux.intel.com, john.mcnamara@intel.com
Subject: [dpdk-dev] [PATCH] doc: add known issue for virtio TSO with clones
Date: Mon, 6 Feb 2017 14:16:53 +0100 [thread overview]
Message-ID: <1486387013-1706-1-git-send-email-olivier.matz@6wind.com> (raw)
Document the issue with Tso on shared packets.
Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
---
doc/guides/rel_notes/known_issues.rst | 31 +++++++++++++++++++++++++++++++
1 file changed, 31 insertions(+)
diff --git a/doc/guides/rel_notes/known_issues.rst b/doc/guides/rel_notes/known_issues.rst
index 018e999..f149ac7 100644
--- a/doc/guides/rel_notes/known_issues.rst
+++ b/doc/guides/rel_notes/known_issues.rst
@@ -666,3 +666,34 @@ uio pci generic module bind failed in X710/XL710/XXV710
**Driver/Module**:
Poll Mode Driver (PMD).
+
+
+virtio tx_burst() function cannot do TSO on shared packets
+----------------------------------------------------------
+
+**Description**:
+ The standard TX function of virtio driver does not manage shared
+ packets properly when doing TSO. These packets should be read-only
+ but the driver modifies them.
+
+ When doing TSO, the virtio standard expects that the L4 checksum is
+ set to the pseudo header checksum in the packet data, which is
+ different than the DPDK API. The driver patches the L4 checksum to
+ conform to the virtio standard, but this solution is invalid when
+ dealing with shared packets (clones), because the packet data should
+ not be modified.
+
+**Implication**:
+ In this situation, the shared data will be modified by the driver,
+ potentially causing race conditions with the other users of the mbuf
+ data.
+
+**Resolution/Workaround**:
+ The workaround in the application is to ensure that the network
+ headers in the packet data are not shared.
+
+**Affected Environment/Platform**:
+ Virtual machines running a virtio driver.
+
+**Driver/Module**:
+ Poll Mode Driver (PMD).
--
2.8.1
next reply other threads:[~2017-02-06 13:17 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-06 13:16 Olivier Matz [this message]
2017-02-06 23:10 ` Stephen Hemminger
2017-02-09 15:05 ` Thomas Monjalon
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