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| author | Stefan Hajnoczi <stefanha@redhat.com> | 2022-11-17 11:55:54 -0500 |
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| committer | Stefan Hajnoczi <stefanha@redhat.com> | 2022-11-21 09:28:43 -0500 |
| commit | 6d71357a3b651ec9db126e4862b77e13165427f5 (patch) | |
| tree | 125f52b2e4b093921b4aacf87579943d2aa2582b /subprojects/libvhost-user/libvhost-user.c | |
| parent | c74831a02c818f89d10f5475cd0fb9ba40bfb2a8 (diff) | |
| download | focaccia-qemu-6d71357a3b651ec9db126e4862b77e13165427f5.tar.gz focaccia-qemu-6d71357a3b651ec9db126e4862b77e13165427f5.zip | |
rtl8139: honor large send MSS value
The Large-Send Task Offload Tx Descriptor (9.2.1 Transmit) has a Large-Send MSS value where the driver specifies the MSS. See the datasheet here: http://realtek.info/pdf/rtl8139cp.pdf The code ignores this value and uses a hardcoded MSS of 1500 bytes instead. When the MTU is less than 1500 bytes the hardcoded value results in IP fragmentation and poor performance. Use the Large-Send MSS value to correctly size Large-Send packets. Jason Wang <jasowang@redhat.com> noticed that the Large-Send MSS value mask was incorrect so it is adjusted to match the datasheet and Linux 8139cp driver. This issue was discussed in the past here: https://lore.kernel.org/all/20161114162505.GD26664@stefanha-x1.localdomain/ Reported-by: Russell King - ARM Linux <linux@armlinux.org.uk> Reported-by: Tobias Fiebig <tobias+git@fiebig.nl> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1312 Acked-by: Jason Wang <jasowang@redhat.com> Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Message-Id: <20221117165554.1773409-4-stefanha@redhat.com>
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