FAILED: patch "[PATCH] hwmon: (powerz) Avoid cacheline sharing for DMA buffer" failed to apply to 6.18-stable tree

The patch below does not apply to the 6.18-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x 3023c050af3600bf451153335dea5e073c9a3088
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026050159-extinct-precision-0d22@gregkh' --subject-prefix 'PATCH 6.18.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 3023c050af3600bf451153335dea5e073c9a3088 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thomas=20Wei=C3=9Fschuh?= <[email protected]>
Date: Wed, 8 Apr 2026 20:45:50 +0200
Subject: [PATCH] hwmon: (powerz) Avoid cacheline sharing for DMA buffer
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Depending on the architecture the transfer buffer may share a cacheline with the following mutex. As the buffer may be used for DMA, that is problematic.

Use the high-level DMA helpers to make sure that cacheline sharing can not happen.

Also drop the comment, as the helpers are documentation enough.

https://sashiko.dev/#/message/20260408175814.934BFC19421%40smtp.kernel.org

index 96438f5f05d4..6e1359144cab 100644
@@ -6,6 +6,7 @@
 
 #include <linux/completion.h>
 #include <linux/device.h>
+#include <linux/dma-mapping.h>
 #include <linux/hwmon.h>
 #include <linux/module.h>
 #include <linux/mutex.h>

@@ -33,7 +34,9 @@ struct powerz_sensor_data {
 } __packed;
 
 struct powerz_priv {
-	char transfer_buffer[64];	/* first member to satisfy DMA alignment */
+	__dma_from_device_group_begin();
+	char transfer_buffer[64];
+	__dma_from_device_group_end();
 	struct mutex mutex;
 	struct completion completion;
 	struct urb *urb;

From: "Michael S. Tsirkin" <[email protected]>

[ Upstream commit ca085faabb42c31ee204235facc5a430cb9e78a9 ]

When a structure contains a buffer that DMA writes to alongside fields that the CPU writes to, cache line sharing between the DMA buffer and CPU-written fields can cause data corruption on non-cache-coherent platforms.

Add __dma_from_device_group_begin()/end() annotations to ensure proper alignment to prevent this:

struct my_device {
	spinlock_t lock1;
	__dma_from_device_group_begin();
	char dma_buffer1[16];
	char dma_buffer2[16];
	__dma_from_device_group_end();
	spinlock_t lock2;
};

Message-ID: <19163086d5e4704c316f18f6da06bc1c72968904.1767601130.git.mst@redhat.com>

Stable-dep-of: 3023c050af36 ("hwmon: (powerz) Avoid cacheline sharing for DMA buffer")

---
 include/linux/dma-mapping.h | 13 +++++++++++++
 1 file changed, 13 insertions(+)

index 3e63046b899bc..f46a0848cb247 100644
@@ -7,6 +7,7 @@
 #include <linux/dma-direction.h>
 #include <linux/scatterlist.h>
 #include <linux/bug.h>
+#include <linux/cache.h>
 
 /**
  * List of possible attributes associated with a DMA mapping. The semantics

@@ -710,6 +711,18 @@ static inline int dma_get_cache_alignment(void)
 }
 #endif
 
+#ifdef ARCH_HAS_DMA_MINALIGN
+#define ____dma_from_device_aligned __aligned(ARCH_DMA_MINALIGN)
+#else
+#define ____dma_from_device_aligned
+#endif
+/* Mark start of DMA buffer */
+#define __dma_from_device_group_begin(GROUP)			\
+	__cacheline_group_begin(GROUP) ____dma_from_device_aligned
+/* Mark end of DMA buffer */
+#define __dma_from_device_group_end(GROUP)			\
+	__cacheline_group_end(GROUP) ____dma_from_device_aligned
+
 static inline void *dmam_alloc_coherent(struct device *dev, size_t size,
 		dma_addr_t *dma_handle, gfp_t gfp)
 {

2.53.0

From: Thomas Weißschuh <[email protected]>

[ Upstream commit 3023c050af3600bf451153335dea5e073c9a3088 ]

Depending on the architecture the transfer buffer may share a cacheline with the following mutex. As the buffer may be used for DMA, that is problematic.

Use the high-level DMA helpers to make sure that cacheline sharing can not happen.

Also drop the comment, as the helpers are documentation enough.

https://sashiko.dev/#/message/20260408175814.934BFC19421%40smtp.kernel.org

---
 drivers/hwmon/powerz.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

index a75b941bd6e2f..dbe6b7ee16446 100644
@@ -6,6 +6,7 @@
 
 #include <linux/completion.h>
 #include <linux/device.h>
+#include <linux/dma-mapping.h>
 #include <linux/hwmon.h>
 #include <linux/module.h>
 #include <linux/mutex.h>

@@ -33,7 +34,9 @@ struct powerz_sensor_data {
 } __packed;
 
 struct powerz_priv {
-	char transfer_buffer[64];	/* first member to satisfy DMA alignment */
+	__dma_from_device_group_begin();
+	char transfer_buffer[64];
+	__dma_from_device_group_end();
 	struct mutex mutex;
 	struct completion completion;
 	struct urb *urb;

2.53.0