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commit: 58d68cf3c08d4109201e1a36068a7e366d6dde84 |
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Author: Mike Pagano <mpagano <AT> gentoo <DOT> org> |
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AuthorDate: Mon Mar 28 22:04:23 2022 +0000 |
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Commit: Mike Pagano <mpagano <AT> gentoo <DOT> org> |
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CommitDate: Mon Mar 28 22:04:23 2022 +0000 |
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URL: https://gitweb.gentoo.org/proj/linux-patches.git/commit/?id=58d68cf3 |
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|
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Revert swiotlb: rework fix info leak with DMA_FROM_DEVICE |
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|
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Bug: https://bugs.gentoo.org/835513 |
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|
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Signed-off-by: Mike Pagano <mpagano <AT> gentoo.org> |
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|
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0000_README | 4 + |
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...rework-fix-info-leak-with-dma_from_device.patch | 187 +++++++++++++++++++++ |
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2 files changed, 191 insertions(+) |
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|
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diff --git a/0000_README b/0000_README |
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index 684989ae..19269be2 100644 |
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--- a/0000_README |
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+++ b/0000_README |
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@@ -63,6 +63,10 @@ Patch: 2400_mt76-mt7921e-fix-possible-probe-failure-after-reboot.patch |
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From: https://patchwork.kernel.org/project/linux-wireless/patch/70e27cbc652cbdb78277b9c691a3a5ba02653afb.1641540175.git.objelf@×××××.com/ |
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Desc: mt76: mt7921e: fix possible probe failure after reboot |
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|
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+Patch: 2410_revert-swiotlb-rework-fix-info-leak-with-dma_from_device.patch |
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+From: https://git.kernel.org/pub/scm/linux/kernel/git/stable/stable-queue.git |
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+Desc: Revert swiotlb: rework fix info leak with DMA_FROM_DEVICE |
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+ |
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Patch: 2900_tmp513-Fix-build-issue-by-selecting-CONFIG_REG.patch |
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From: https://bugs.gentoo.org/710790 |
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Desc: tmp513 requies REGMAP_I2C to build. Select it by default in Kconfig. See bug #710790. Thanks to Phil Stracchino |
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|
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diff --git a/2410_revert-swiotlb-rework-fix-info-leak-with-dma_from_device.patch b/2410_revert-swiotlb-rework-fix-info-leak-with-dma_from_device.patch |
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new file mode 100644 |
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index 00000000..69476ab1 |
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--- /dev/null |
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+++ b/2410_revert-swiotlb-rework-fix-info-leak-with-dma_from_device.patch |
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@@ -0,0 +1,187 @@ |
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+From bddac7c1e02ba47f0570e494c9289acea3062cc1 Mon Sep 17 00:00:00 2001 |
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+From: Linus Torvalds <torvalds@××××××××××××××××.org> |
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+Date: Sat, 26 Mar 2022 10:42:04 -0700 |
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+Subject: Revert "swiotlb: rework "fix info leak with DMA_FROM_DEVICE"" |
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+MIME-Version: 1.0 |
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+Content-Type: text/plain; charset=UTF-8 |
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+Content-Transfer-Encoding: 8bit |
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+ |
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+From: Linus Torvalds <torvalds@××××××××××××××××.org> |
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+ |
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+commit bddac7c1e02ba47f0570e494c9289acea3062cc1 upstream. |
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+ |
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+This reverts commit aa6f8dcbab473f3a3c7454b74caa46d36cdc5d13. |
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+ |
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+It turns out this breaks at least the ath9k wireless driver, and |
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+possibly others. |
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+ |
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+What the ath9k driver does on packet receive is to set up the DMA |
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+transfer with: |
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+ |
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+ int ath_rx_init(..) |
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+ .. |
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+ bf->bf_buf_addr = dma_map_single(sc->dev, skb->data, |
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+ common->rx_bufsize, |
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+ DMA_FROM_DEVICE); |
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+ |
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+and then the receive logic (through ath_rx_tasklet()) will fetch |
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+incoming packets |
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+ |
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+ static bool ath_edma_get_buffers(..) |
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+ .. |
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+ dma_sync_single_for_cpu(sc->dev, bf->bf_buf_addr, |
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+ common->rx_bufsize, DMA_FROM_DEVICE); |
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+ |
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+ ret = ath9k_hw_process_rxdesc_edma(ah, rs, skb->data); |
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+ if (ret == -EINPROGRESS) { |
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+ /*let device gain the buffer again*/ |
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+ dma_sync_single_for_device(sc->dev, bf->bf_buf_addr, |
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+ common->rx_bufsize, DMA_FROM_DEVICE); |
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+ return false; |
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+ } |
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+ |
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+and it's worth noting how that first DMA sync: |
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+ |
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+ dma_sync_single_for_cpu(..DMA_FROM_DEVICE); |
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+ |
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+is there to make sure the CPU can read the DMA buffer (possibly by |
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+copying it from the bounce buffer area, or by doing some cache flush). |
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+The iommu correctly turns that into a "copy from bounce bufer" so that |
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+the driver can look at the state of the packets. |
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+ |
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+In the meantime, the device may continue to write to the DMA buffer, but |
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+we at least have a snapshot of the state due to that first DMA sync. |
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+ |
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+But that _second_ DMA sync: |
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+ |
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+ dma_sync_single_for_device(..DMA_FROM_DEVICE); |
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+ |
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+is telling the DMA mapping that the CPU wasn't interested in the area |
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+because the packet wasn't there. In the case of a DMA bounce buffer, |
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+that is a no-op. |
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+ |
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+Note how it's not a sync for the CPU (the "for_device()" part), and it's |
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+not a sync for data written by the CPU (the "DMA_FROM_DEVICE" part). |
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+ |
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+Or rather, it _should_ be a no-op. That's what commit aa6f8dcbab47 |
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+broke: it made the code bounce the buffer unconditionally, and changed |
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+the DMA_FROM_DEVICE to just unconditionally and illogically be |
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+DMA_TO_DEVICE. |
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+ |
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+[ Side note: purely within the confines of the swiotlb driver it wasn't |
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+ entirely illogical: The reason it did that odd DMA_FROM_DEVICE -> |
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+ DMA_TO_DEVICE conversion thing is because inside the swiotlb driver, |
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+ it uses just a swiotlb_bounce() helper that doesn't care about the |
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+ whole distinction of who the sync is for - only which direction to |
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+ bounce. |
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+ |
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+ So it took the "sync for device" to mean that the CPU must have been |
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+ the one writing, and thought it meant DMA_TO_DEVICE. ] |
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+ |
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+Also note how the commentary in that commit was wrong, probably due to |
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+that whole confusion, claiming that the commit makes the swiotlb code |
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+ |
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+ "bounce unconditionally (that is, also |
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+ when dir == DMA_TO_DEVICE) in order do avoid synchronising back stale |
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+ data from the swiotlb buffer" |
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+ |
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+which is nonsensical for two reasons: |
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+ |
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+ - that "also when dir == DMA_TO_DEVICE" is nonsensical, as that was |
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+ exactly when it always did - and should do - the bounce. |
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+ |
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+ - since this is a sync for the device (not for the CPU), we're clearly |
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+ fundamentally not coping back stale data from the bounce buffers at |
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+ all, because we'd be copying *to* the bounce buffers. |
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+ |
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+So that commit was just very confused. It confused the direction of the |
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+synchronization (to the device, not the cpu) with the direction of the |
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+DMA (from the device). |
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+ |
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+Reported-and-bisected-by: Oleksandr Natalenko <oleksandr@×××××××××.name> |
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+Reported-by: Olha Cherevyk <olha.cherevyk@×××××.com> |
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+Cc: Halil Pasic <pasic@×××××××××.com> |
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+Cc: Christoph Hellwig <hch@×××.de> |
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+Cc: Kalle Valo <kvalo@××××××.org> |
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+Cc: Robin Murphy <robin.murphy@×××.com> |
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+Cc: Toke Høiland-Jørgensen <toke@××××.dk> |
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+Cc: Maxime Bizon <mbizon@×××××××.fr> |
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+Cc: Johannes Berg <johannes@××××××××××××.net> |
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+Signed-off-by: Linus Torvalds <torvalds@××××××××××××××××.org> |
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+Signed-off-by: Greg Kroah-Hartman <gregkh@×××××××××××××××.org> |
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+--- |
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+ Documentation/core-api/dma-attributes.rst | 8 ++++++++ |
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+ include/linux/dma-mapping.h | 8 ++++++++ |
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+ kernel/dma/swiotlb.c | 23 ++++++++--------------- |
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+ 3 files changed, 24 insertions(+), 15 deletions(-) |
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+ |
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+--- a/Documentation/core-api/dma-attributes.rst |
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++++ b/Documentation/core-api/dma-attributes.rst |
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+@@ -130,3 +130,11 @@ accesses to DMA buffers in both privileg |
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+ subsystem that the buffer is fully accessible at the elevated privilege |
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+ level (and ideally inaccessible or at least read-only at the |
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+ lesser-privileged levels). |
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++ |
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++DMA_ATTR_OVERWRITE |
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++------------------ |
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++ |
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++This is a hint to the DMA-mapping subsystem that the device is expected to |
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++overwrite the entire mapped size, thus the caller does not require any of the |
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++previous buffer contents to be preserved. This allows bounce-buffering |
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++implementations to optimise DMA_FROM_DEVICE transfers. |
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+--- a/include/linux/dma-mapping.h |
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++++ b/include/linux/dma-mapping.h |
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+@@ -62,6 +62,14 @@ |
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+ #define DMA_ATTR_PRIVILEGED (1UL << 9) |
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+ |
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+ /* |
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++ * This is a hint to the DMA-mapping subsystem that the device is expected |
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++ * to overwrite the entire mapped size, thus the caller does not require any |
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++ * of the previous buffer contents to be preserved. This allows |
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++ * bounce-buffering implementations to optimise DMA_FROM_DEVICE transfers. |
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++ */ |
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++#define DMA_ATTR_OVERWRITE (1UL << 10) |
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++ |
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++/* |
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+ * A dma_addr_t can hold any valid DMA or bus address for the platform. It can |
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+ * be given to a device to use as a DMA source or target. It is specific to a |
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+ * given device and there may be a translation between the CPU physical address |
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+--- a/kernel/dma/swiotlb.c |
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++++ b/kernel/dma/swiotlb.c |
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+@@ -627,14 +627,10 @@ phys_addr_t swiotlb_tbl_map_single(struc |
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+ for (i = 0; i < nr_slots(alloc_size + offset); i++) |
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+ mem->slots[index + i].orig_addr = slot_addr(orig_addr, i); |
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+ tlb_addr = slot_addr(mem->start, index) + offset; |
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+- /* |
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+- * When dir == DMA_FROM_DEVICE we could omit the copy from the orig |
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+- * to the tlb buffer, if we knew for sure the device will |
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+- * overwirte the entire current content. But we don't. Thus |
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+- * unconditional bounce may prevent leaking swiotlb content (i.e. |
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+- * kernel memory) to user-space. |
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+- */ |
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+- swiotlb_bounce(dev, tlb_addr, mapping_size, DMA_TO_DEVICE); |
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++ if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) && |
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++ (!(attrs & DMA_ATTR_OVERWRITE) || dir == DMA_TO_DEVICE || |
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++ dir == DMA_BIDIRECTIONAL)) |
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++ swiotlb_bounce(dev, tlb_addr, mapping_size, DMA_TO_DEVICE); |
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+ return tlb_addr; |
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+ } |
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+ |
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+@@ -701,13 +697,10 @@ void swiotlb_tbl_unmap_single(struct dev |
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+ void swiotlb_sync_single_for_device(struct device *dev, phys_addr_t tlb_addr, |
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+ size_t size, enum dma_data_direction dir) |
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+ { |
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+- /* |
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+- * Unconditional bounce is necessary to avoid corruption on |
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+- * sync_*_for_cpu or dma_ummap_* when the device didn't overwrite |
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+- * the whole lengt of the bounce buffer. |
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+- */ |
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+- swiotlb_bounce(dev, tlb_addr, size, DMA_TO_DEVICE); |
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+- BUG_ON(!valid_dma_direction(dir)); |
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++ if (dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL) |
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++ swiotlb_bounce(dev, tlb_addr, size, DMA_TO_DEVICE); |
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++ else |
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++ BUG_ON(dir != DMA_FROM_DEVICE); |
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+ } |
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+ |
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+ void swiotlb_sync_single_for_cpu(struct device *dev, phys_addr_t tlb_addr, |