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Date: Sat, 26 Sep 2020 04:24:53 +0000
From: John Stultz <john.stultz@...aro.org>
To: lkml <linux-kernel@...r.kernel.org>
Cc: John Stultz <john.stultz@...aro.org>,
Sumit Semwal <sumit.semwal@...aro.org>,
Liam Mark <lmark@...eaurora.org>,
Laura Abbott <labbott@...nel.org>,
Brian Starkey <Brian.Starkey@....com>,
Hridya Valsaraju <hridya@...gle.com>,
Suren Baghdasaryan <surenb@...gle.com>,
Sandeep Patil <sspatil@...gle.com>,
Ørjan Eide <orjan.eide@....com>,
Robin Murphy <robin.murphy@....com>,
Ezequiel Garcia <ezequiel@...labora.com>,
Simon Ser <contact@...rsion.fr>,
James Jones <jajones@...dia.com>, linux-media@...r.kernel.org,
dri-devel@...ts.freedesktop.org
Subject: [RFC][PATCH 6/6] dma-buf: heaps: Skip sync if not mapped
This patch is basically a port of Ørjan Eide's similar patch for ION
https://lore.kernel.org/lkml/20200414134629.54567-1-orjan.eide@arm.com/
Only sync the sg-list of dma-buf heap attachment when the attachment
is actually mapped on the device.
dma-bufs may be synced at any time. It can be reached from user space
via DMA_BUF_IOCTL_SYNC, so there are no guarantees from callers on when
syncs may be attempted, and dma_buf_end_cpu_access() and
dma_buf_begin_cpu_access() may not be paired.
Since the sg_list's dma_address isn't set up until the buffer is used
on the device, and dma_map_sg() is called on it, the dma_address will be
NULL if sync is attempted on the dma-buf before it's mapped on a device.
Before v5.0 (commit 55897af63091 ("dma-direct: merge swiotlb_dma_ops
into the dma_direct code")) this was a problem as the dma-api (at least
the swiotlb_dma_ops on arm64) would use the potentially invalid
dma_address. How that failed depended on how the device handled physical
address 0. If 0 was a valid address to physical ram, that page would get
flushed a lot, while the actual pages in the buffer would not get synced
correctly. While if 0 is an invalid physical address it may cause a
fault and trigger a crash.
In v5.0 this was incidentally fixed by commit 55897af63091 ("dma-direct:
merge swiotlb_dma_ops into the dma_direct code"), as this moved the
dma-api to use the page pointer in the sg_list, and (for Ion buffers at
least) this will always be valid if the sg_list exists at all.
But, this issue is re-introduced in v5.3 with
commit 449fa54d6815 ("dma-direct: correct the physical addr in
dma_direct_sync_sg_for_cpu/device") moves the dma-api back to the old
behaviour and picks the dma_address that may be invalid.
dma-buf core doesn't ensure that the buffer is mapped on the device, and
thus have a valid sg_list, before calling the exporter's
begin_cpu_access.
Logic and commit message originally by: Ørjan Eide <orjan.eide@....com>
Cc: Sumit Semwal <sumit.semwal@...aro.org>
Cc: Liam Mark <lmark@...eaurora.org>
Cc: Laura Abbott <labbott@...nel.org>
Cc: Brian Starkey <Brian.Starkey@....com>
Cc: Hridya Valsaraju <hridya@...gle.com>
Cc: Suren Baghdasaryan <surenb@...gle.com>
Cc: Sandeep Patil <sspatil@...gle.com>
Cc: Ørjan Eide <orjan.eide@....com>
Cc: Robin Murphy <robin.murphy@....com>
Cc: Ezequiel Garcia <ezequiel@...labora.com>
Cc: Simon Ser <contact@...rsion.fr>
Cc: James Jones <jajones@...dia.com>
Cc: linux-media@...r.kernel.org
Cc: dri-devel@...ts.freedesktop.org
Signed-off-by: John Stultz <john.stultz@...aro.org>
---
drivers/dma-buf/heaps/cma_heap.c | 10 ++++++++++
drivers/dma-buf/heaps/system_heap.c | 10 ++++++++++
2 files changed, 20 insertions(+)
diff --git a/drivers/dma-buf/heaps/cma_heap.c b/drivers/dma-buf/heaps/cma_heap.c
index 3adfdbed0829..b6ab0392ad9a 100644
--- a/drivers/dma-buf/heaps/cma_heap.c
+++ b/drivers/dma-buf/heaps/cma_heap.c
@@ -44,6 +44,7 @@ struct dma_heap_attachment {
struct device *dev;
struct sg_table table;
struct list_head list;
+ bool mapped;
};
static int cma_heap_attach(struct dma_buf *dmabuf,
@@ -68,6 +69,7 @@ static int cma_heap_attach(struct dma_buf *dmabuf,
a->dev = attachment->dev;
INIT_LIST_HEAD(&a->list);
+ a->mapped = false;
attachment->priv = a;
@@ -101,6 +103,7 @@ static struct sg_table *cma_heap_map_dma_buf(struct dma_buf_attachment *attachme
if (!dma_map_sg(attachment->dev, table->sgl, table->nents,
direction))
table = ERR_PTR(-ENOMEM);
+ a->mapped = true;
return table;
}
@@ -108,6 +111,9 @@ static void cma_heap_unmap_dma_buf(struct dma_buf_attachment *attachment,
struct sg_table *table,
enum dma_data_direction direction)
{
+ struct dma_heap_attachment *a = attachment->priv;
+
+ a->mapped = false;
dma_unmap_sg(attachment->dev, table->sgl, table->nents, direction);
}
@@ -123,6 +129,8 @@ static int cma_heap_dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
mutex_lock(&buffer->lock);
list_for_each_entry(a, &buffer->attachments, list) {
+ if (!a->mapped)
+ continue;
dma_sync_sg_for_cpu(a->dev, a->table.sgl, a->table.nents,
direction);
}
@@ -142,6 +150,8 @@ static int cma_heap_dma_buf_end_cpu_access(struct dma_buf *dmabuf,
mutex_lock(&buffer->lock);
list_for_each_entry(a, &buffer->attachments, list) {
+ if (!a->mapped)
+ continue;
dma_sync_sg_for_device(a->dev, a->table.sgl, a->table.nents,
direction);
}
diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c
index 9f57b4c8ae69..8a523b6fd51a 100644
--- a/drivers/dma-buf/heaps/system_heap.c
+++ b/drivers/dma-buf/heaps/system_heap.c
@@ -38,6 +38,7 @@ struct dma_heap_attachment {
struct device *dev;
struct sg_table *table;
struct list_head list;
+ bool mapped;
};
#define HIGH_ORDER_GFP (((GFP_HIGHUSER | __GFP_ZERO | __GFP_NOWARN \
@@ -94,6 +95,7 @@ static int system_heap_attach(struct dma_buf *dmabuf,
a->table = table;
a->dev = attachment->dev;
INIT_LIST_HEAD(&a->list);
+ a->mapped = false;
attachment->priv = a;
@@ -128,6 +130,7 @@ static struct sg_table *system_heap_map_dma_buf(struct dma_buf_attachment *attac
if (!dma_map_sg(attachment->dev, table->sgl, table->nents, direction))
return ERR_PTR(-ENOMEM);
+ a->mapped = true;
return table;
}
@@ -135,6 +138,9 @@ static void system_heap_unmap_dma_buf(struct dma_buf_attachment *attachment,
struct sg_table *table,
enum dma_data_direction direction)
{
+ struct dma_heap_attachment *a = attachment->priv;
+
+ a->mapped = false;
dma_unmap_sg(attachment->dev, table->sgl, table->nents, direction);
}
@@ -151,6 +157,8 @@ static int system_heap_dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
invalidate_kernel_vmap_range(buffer->vaddr, buffer->len);
list_for_each_entry(a, &buffer->attachments, list) {
+ if (!a->mapped)
+ continue;
dma_sync_sg_for_cpu(a->dev, a->table->sgl, a->table->nents,
direction);
}
@@ -171,6 +179,8 @@ static int system_heap_dma_buf_end_cpu_access(struct dma_buf *dmabuf,
flush_kernel_vmap_range(buffer->vaddr, buffer->len);
list_for_each_entry(a, &buffer->attachments, list) {
+ if (!a->mapped)
+ continue;
dma_sync_sg_for_device(a->dev, a->table->sgl, a->table->nents,
direction);
}
--
2.17.1
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