[Buildroot] [PATCH v2] configs/visionfive2_defconfig: bump Linux to 6.18.55

[Buildroot] [PATCH v2] configs/visionfive2_defconfig: bump Linux to 6.18.55

[Fengwei Tan]

When running iperf3 with Linux 6.18.51 on VisionFive 2, one CPU core
stays at 100% load during the test, while network throughput is limited
to approximately 793 Mbits/sec:

[ ID] Interval           Transfer     Bitrate
[  5]   0.00-10.01  sec   945 MBytes   793 Mbits/sec                  receiver

The regression was introduced in Linux 6.14 by commit df542f669307
("net: stmmac: Switch to zero-copy in non-XDP RX path"). It leads to
misaligned access exceptions when parsing packet headers. During the
iperf3 test, perf stat reported approximately 9.6 million alignment
faults over 5 seconds:

$ perf stat -a -e alignment-faults -- sleep 5

 Performance counter stats for 'system wide':

           9620073      alignment-faults

       5.029337000 seconds time elapsed

The kernel must emulate these unaligned accesses, resulting in
significant overhead.

The issue was fixed in Linux 6.18.52 [1]. Bump Linux to 6.18.55, the
latest stable release at the time of writing, to include the fix.

[1] https://lore.kernel.org/all/2026091704-CVE-2026-90059-36e6@gregkh

Fixes: 98aa14a186e1 ("configs/visionfive2: bump Linux to 6.18.51, U-Boot to 2026.07, and OpenSBI to 1.8.1")
Assisted-by: LLM
Signed-off-by: Fengwei Tan <tfx2001@outlook.com>
---
Hello all,

This patch fixes a performance issue on the VisionFive 2, caused by
misaligned access when the Linux kernel network stack parses packet
headers.

I noticed this issue while running iperf3 tests on the VisionFive 2
board. I captured perf data [1] and analyzed it with LLM, which
quickly identified the relevant upstream kernel commit and the
corresponding lore archive [2].

I rebuilt Linux 6.18.51 with the fix patch [3] applied and retested; the
issue was resolved. So I am pretty sure this issue was introduced by the
commit identified by the LLM.

[1] https://gist.github.com/tfx2001/f1f10ee1274acb7063ef1def5f2b119a
[2] https://lore.kernel.org/all/2026091704-CVE-2026-90059-36e6@gregkh/
[3] https://git.kernel.org/stable/c/2ea42936416b29cca42b2c7bc7d3d3768f77c199
---
Changes in v2:
- Bump Linux to 6.18.55
- Link to v1: https://patch.msgid.link/SY8P300MB00411684A8A44ED2157BB57AB5942@SY8P300MB0041.AUSP300.PROD.OUTLOOK.COM
---
 board/visionfive2/patches/linux/linux.hash | 2 +-
 configs/visionfive2_defconfig              | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/board/visionfive2/patches/linux/linux.hash b/board/visionfive2/patches/linux/linux.hash
index b2cfc9b7e7..63b8047edc 100644
--- a/board/visionfive2/patches/linux/linux.hash
+++ b/board/visionfive2/patches/linux/linux.hash
@@ -1,2 +1,2 @@
 # Locally calculated
-sha256  ba2f60f858bf4d1f929101faa356c93dc8b925b17aaa9f95eabd4627758df613  linux-6.18.51.tar.xz
+sha256  f410638061a165c12f42ab871d2f3fcd525515359b5faeee80969cff84524df9  linux-6.18.55.tar.xz
diff --git a/configs/visionfive2_defconfig b/configs/visionfive2_defconfig
index 7ce605b84b..6ae6f25a8a 100644
--- a/configs/visionfive2_defconfig
+++ b/configs/visionfive2_defconfig
@@ -7,7 +7,7 @@ BR2_ROOTFS_OVERLAY="board/visionfive2/overlay"
 BR2_ROOTFS_POST_IMAGE_SCRIPT="board/visionfive2/post-image.sh"
 BR2_LINUX_KERNEL=y
 BR2_LINUX_KERNEL_CUSTOM_VERSION=y
-BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="6.18.51"
+BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="6.18.55"
 BR2_LINUX_KERNEL_USE_CUSTOM_CONFIG=y
 BR2_LINUX_KERNEL_CUSTOM_CONFIG_FILE="board/visionfive2/linux_defconfig"
 BR2_LINUX_KERNEL_DTS_SUPPORT=y

---
base-commit: 1ab8f8ef5af5a170a1ecbea3209ca39afd49194c
change-id: 20261007-visionfive2-bump-linux-version-0de383d488d3

Best regards,
--  
Fengwei Tan <tfx2001@outlook.com>
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Re: [Buildroot] [PATCH v2] configs/visionfive2_defconfig: bump Linux to 6.18.55

[Thomas Petazzoni via buildroot]

On Sun, Oct 11, 2026 at 12:31:48AM +0800, Fengwei Tan wrote:
> When running iperf3 with Linux 6.18.51 on VisionFive 2, one CPU core
> stays at 100% load during the test, while network throughput is limited
> to approximately 793 Mbits/sec:
> 
> [ ID] Interval           Transfer     Bitrate
> [  5]   0.00-10.01  sec   945 MBytes   793 Mbits/sec                  receiver
> 
> The regression was introduced in Linux 6.14 by commit df542f669307
> ("net: stmmac: Switch to zero-copy in non-XDP RX path"). It leads to
> misaligned access exceptions when parsing packet headers. During the
> iperf3 test, perf stat reported approximately 9.6 million alignment
> faults over 5 seconds:
> 
> $ perf stat -a -e alignment-faults -- sleep 5
> 
>  Performance counter stats for 'system wide':
> 
>            9620073      alignment-faults
> 
>        5.029337000 seconds time elapsed
> 
> The kernel must emulate these unaligned accesses, resulting in
> significant overhead.
> 
> The issue was fixed in Linux 6.18.52 [1]. Bump Linux to 6.18.55, the
> latest stable release at the time of writing, to include the fix.
> 
> [1] https://lore.kernel.org/all/2026091704-CVE-2026-90059-36e6@gregkh
> 
> Fixes: 98aa14a186e1 ("configs/visionfive2: bump Linux to 6.18.51, U-Boot to 2026.07, and OpenSBI to 1.8.1")
> Assisted-by: LLM
> Signed-off-by: Fengwei Tan <tfx2001@outlook.com>

Applied to master, thanks!

Best regards,

Thomas Petazzoni
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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