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Message-ID: <20240509144616.938519-1-aleksander.lobakin@intel.com>
Date: Thu, 9 May 2024 16:46:16 +0200
From: Alexander Lobakin <aleksander.lobakin@...el.com>
To: Christoph Hellwig <hch@....de>
Cc: Alexander Lobakin <aleksander.lobakin@...el.com>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Marek Szyprowski <m.szyprowski@...sung.com>,
Steven Price <steven.price@....com>,
Robin Murphy <robin.murphy@....com>,
Joerg Roedel <joro@...tes.org>,
Will Deacon <will@...nel.org>,
"Rafael J. Wysocki" <rafael@...nel.org>,
Magnus Karlsson <magnus.karlsson@...el.com>,
nex.sw.ncis.osdt.itp.upstreaming@...el.com,
bpf@...r.kernel.org,
netdev@...r.kernel.org,
iommu@...ts.linux.dev,
linux-kernel@...r.kernel.org
Subject: [PATCH] dma: fix DMA sync for drivers not calling dma_set_mask*()
There are several reports that the DMA sync shortcut broke non-coherent
devices.
dev->dma_need_sync is false after the &device allocation and if a driver
didn't call dma_set_mask*(), it will still be false even if the device
is not DMA-coherent and thus needs synchronizing. Due to historical
reasons, there's still a lot of drivers not calling it.
Invert the boolean, so that the sync will be performed by default and
the shortcut will be enabled only when calling dma_set_mask*().
Reported-by: Marek Szyprowski <m.szyprowski@...sung.com>
Closes: https://lore.kernel.org/lkml/46160534-5003-4809-a408-6b3a3f4921e9@samsung.com
Reported-by: Steven Price <steven.price@....com>
Closes: https://lore.kernel.org/lkml/010686f5-3049-46a1-8230-7752a1b433ff@arm.com
Fixes: 32ba8b823252 ("dma: avoid redundant calls for sync operations")
Signed-off-by: Alexander Lobakin <aleksander.lobakin@...el.com>
---
include/linux/device.h | 4 ++--
include/linux/dma-map-ops.h | 4 ++--
include/linux/dma-mapping.h | 2 +-
kernel/dma/mapping.c | 10 +++++-----
kernel/dma/swiotlb.c | 2 +-
5 files changed, 11 insertions(+), 11 deletions(-)
diff --git a/include/linux/device.h b/include/linux/device.h
index ed95b829f05b..d4b50accff26 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -691,7 +691,7 @@ struct device_physical_location {
* and optionall (if the coherent mask is large enough) also
* for dma allocations. This flag is managed by the dma ops
* instance from ->dma_supported.
- * @dma_need_sync: The device needs performing DMA sync operations.
+ * @dma_skip_sync: DMA sync operations can be skipped for coherent buffers.
*
* At the lowest level, every device in a Linux system is represented by an
* instance of struct device. The device structure contains the information
@@ -805,7 +805,7 @@ struct device {
bool dma_ops_bypass : 1;
#endif
#ifdef CONFIG_DMA_NEED_SYNC
- bool dma_need_sync:1;
+ bool dma_skip_sync:1;
#endif
};
diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h
index 4893cb89cb52..5217b922d29f 100644
--- a/include/linux/dma-map-ops.h
+++ b/include/linux/dma-map-ops.h
@@ -280,8 +280,8 @@ static inline void dma_reset_need_sync(struct device *dev)
{
#ifdef CONFIG_DMA_NEED_SYNC
/* Reset it only once so that the function can be called on hotpath */
- if (unlikely(!dev->dma_need_sync))
- dev->dma_need_sync = true;
+ if (unlikely(dev->dma_skip_sync))
+ dev->dma_skip_sync = false;
#endif
}
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index eb4e15893b6c..f693aafe221f 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -295,7 +295,7 @@ bool __dma_need_sync(struct device *dev, dma_addr_t dma_addr);
static inline bool dma_dev_need_sync(const struct device *dev)
{
/* Always call DMA sync operations when debugging is enabled */
- return dev->dma_need_sync || IS_ENABLED(CONFIG_DMA_API_DEBUG);
+ return !dev->dma_skip_sync || IS_ENABLED(CONFIG_DMA_API_DEBUG);
}
static inline void dma_sync_single_for_cpu(struct device *dev, dma_addr_t addr,
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 3524bc92c37f..3f77c3f8d16d 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -392,7 +392,7 @@ bool __dma_need_sync(struct device *dev, dma_addr_t dma_addr)
if (dma_map_direct(dev, ops))
/*
- * dma_need_sync could've been reset on first SWIOTLB buffer
+ * dma_skip_sync could've been reset on first SWIOTLB buffer
* mapping, but @dma_addr is not necessary an SWIOTLB buffer.
* In this case, fall back to more granular check.
*/
@@ -407,20 +407,20 @@ static void dma_setup_need_sync(struct device *dev)
if (dma_map_direct(dev, ops) || (ops->flags & DMA_F_CAN_SKIP_SYNC))
/*
- * dma_need_sync will be reset to %true on first SWIOTLB buffer
+ * dma_skip_sync will be reset to %false on first SWIOTLB buffer
* mapping, if any. During the device initialization, it's
* enough to check only for the DMA coherence.
*/
- dev->dma_need_sync = !dev_is_dma_coherent(dev);
+ dev->dma_skip_sync = dev_is_dma_coherent(dev);
else if (!ops->sync_single_for_device && !ops->sync_single_for_cpu &&
!ops->sync_sg_for_device && !ops->sync_sg_for_cpu)
/*
* Synchronization is not possible when none of DMA sync ops
* is set.
*/
- dev->dma_need_sync = false;
+ dev->dma_skip_sync = true;
else
- dev->dma_need_sync = true;
+ dev->dma_skip_sync = false;
}
#else /* !CONFIG_DMA_NEED_SYNC */
static inline void dma_setup_need_sync(struct device *dev) { }
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index ae3e593eaadb..068134697cf1 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -1409,7 +1409,7 @@ phys_addr_t swiotlb_tbl_map_single(struct device *dev, phys_addr_t orig_addr,
}
/*
- * If dma_need_sync wasn't set, reset it on first SWIOTLB buffer
+ * If dma_skip_sync was set, reset it on first SWIOTLB buffer
* mapping to always sync SWIOTLB buffers.
*/
dma_reset_need_sync(dev);
--
2.45.0
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