From 85a19a714c4b4702edc59db0a3419f48fffe2b0a Mon Sep 17 00:00:00 2001
From: Jinhua Cao <caojinhua1@huawei.com>
Date: Thu, 17 Feb 2022 17:38:41 +0800
Subject: [PATCH] OvmfPkg: VirtioNetDxe: Extend the RxBufferSize to avoid data
 truncation

1822 net card needs at least 1536 bytes for DMA, even we never negotiate
VIRTIO_NET_F_MRG_RXBUF. The original max size of packet is 15144 which would
cause data trucation. Now we extend the RxBufSize to 9014(Jumbo Frame type)
so that we can avoid it.

Signed-off-by: Jinhua Cao <caojinhua1@huawei.com>
---
 OvmfPkg/Include/IndustryStandard/Virtio095Net.h | 7 +++++++
 OvmfPkg/VirtioNetDxe/SnpInitialize.c            | 3 ++-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/OvmfPkg/Include/IndustryStandard/Virtio095Net.h b/OvmfPkg/Include/IndustryStandard/Virtio095Net.h
index 9c0ed5ed24..28f5cc0899 100644
--- a/OvmfPkg/Include/IndustryStandard/Virtio095Net.h
+++ b/OvmfPkg/Include/IndustryStandard/Virtio095Net.h
@@ -88,4 +88,11 @@ typedef struct {
 #define VIRTIO_NET_S_LINK_UP   BIT0
 #define VIRTIO_NET_S_ANNOUNCE  BIT1
 
+//
+// 1822 net card needs at least 1536 bytes for DMA, even we never negotiate
+// VIRTIO_NET_F_MRG_RXBUF. The original max size of packet is 15144 which would
+// cause data trucation. Now we extend the RxBufSize to 9014(Jumbo Frame type)
+// so that we can avoid it.
+#define VIRTIO_RXBUF_JUMBO_PADDING 7500
+
 #endif // _VIRTIO_0_9_5_NET_H_
diff --git a/OvmfPkg/VirtioNetDxe/SnpInitialize.c b/OvmfPkg/VirtioNetDxe/SnpInitialize.c
index bb3b552d68..6febfea3bb 100644
--- a/OvmfPkg/VirtioNetDxe/SnpInitialize.c
+++ b/OvmfPkg/VirtioNetDxe/SnpInitialize.c
@@ -337,7 +337,8 @@ VirtioNetInitRx (
   //   and Ethernet payload).
   //
   RxBufSize = VirtioNetReqSize +
-              (Dev->Snm.MediaHeaderSize + Dev->Snm.MaxPacketSize);
+              (Dev->Snm.MediaHeaderSize + Dev->Snm.MaxPacketSize) +
+               VIRTIO_RXBUF_JUMBO_PADDING;
 
   //
   // Limit the number of pending RX packets if the queue is big. The division
-- 
2.27.0