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authorChristian König <christian.koenig@amd.com>2018-07-03 16:42:26 +0200
committerChristian König <christian.koenig@amd.com>2019-10-24 09:18:09 +0200
commit15fd552d186cb0df34b9d36a07dd6677c4da56bc (patch)
treefbe76ba4a2cf559647313f0ae96caeb43da3027e /drivers/dma-buf/dma-buf.c
parentdrm/tegra: Move drm_dp_link helpers to Tegra DRM (diff)
downloadlinux-15fd552d186cb0df34b9d36a07dd6677c4da56bc.tar.xz
linux-15fd552d186cb0df34b9d36a07dd6677c4da56bc.zip
dma-buf: change DMA-buf locking convention v3
This patch is a stripped down version of the locking changes necessary to support dynamic DMA-buf handling. It adds a dynamic flag for both importers as well as exporters so that drivers can choose if they want the reservation object locked or unlocked during mapping of attachments. For compatibility between drivers we cache the DMA-buf mapping during attaching an importer as soon as exporter/importer disagree on the dynamic handling. Issues and solutions we considered: - We can't change all existing drivers, and existing improters have strong opinions about which locks they're holding while calling dma_buf_attachment_map/unmap. Exporters also have strong opinions about which locks they can acquire in their ->map/unmap callbacks, levaing no room for change. The solution to avoid this was to move the actual map/unmap out from this call, into the attach/detach callbacks, and cache the mapping. This works because drivers don't call attach/detach from deep within their code callchains (like deep in memory management code called from cs/execbuf ioctl), but directly from the fd2handle implementation. - The caching has some troubles on some soc drivers, which set other modes than DMA_BIDIRECTIONAL. We can't have 2 incompatible mappings, and we can't re-create the mapping at _map time due to the above locking fun. We very carefuly step around that by only caching at attach time if the dynamic mode between importer/expoert mismatches. - There's been quite some discussion on dma-buf mappings which need active cache management, which would all break down when caching, plus we don't have explicit flush operations on the attachment side. The solution to this was to shrug and keep the current discrepancy between what the dma-buf docs claim and what implementations do, with the hope that the begin/end_cpu_access hooks are good enough and that all necessary flushing to keep device mappings consistent will be done there. v2: cleanup set_name merge, improve kerneldoc v3: update commit message, kerneldoc and cleanup _debug_show() Signed-off-by: Christian König <christian.koenig@amd.com> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: https://patchwork.freedesktop.org/patch/336788/
Diffstat (limited to 'drivers/dma-buf/dma-buf.c')
-rw-r--r--drivers/dma-buf/dma-buf.c118
1 files changed, 101 insertions, 17 deletions
diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 433d91d710e4..0573879a222a 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -45,10 +45,10 @@ static char *dmabuffs_dname(struct dentry *dentry, char *buffer, int buflen)
size_t ret = 0;
dmabuf = dentry->d_fsdata;
- mutex_lock(&dmabuf->lock);
+ dma_resv_lock(dmabuf->resv, NULL);
if (dmabuf->name)
ret = strlcpy(name, dmabuf->name, DMA_BUF_NAME_LEN);
- mutex_unlock(&dmabuf->lock);
+ dma_resv_unlock(dmabuf->resv);
return dynamic_dname(dentry, buffer, buflen, "/%s:%s",
dentry->d_name.name, ret > 0 ? name : "");
@@ -334,7 +334,7 @@ static long dma_buf_set_name(struct dma_buf *dmabuf, const char __user *buf)
if (IS_ERR(name))
return PTR_ERR(name);
- mutex_lock(&dmabuf->lock);
+ dma_resv_lock(dmabuf->resv, NULL);
if (!list_empty(&dmabuf->attachments)) {
ret = -EBUSY;
kfree(name);
@@ -344,7 +344,7 @@ static long dma_buf_set_name(struct dma_buf *dmabuf, const char __user *buf)
dmabuf->name = name;
out_unlock:
- mutex_unlock(&dmabuf->lock);
+ dma_resv_unlock(dmabuf->resv);
return ret;
}
@@ -403,10 +403,10 @@ static void dma_buf_show_fdinfo(struct seq_file *m, struct file *file)
/* Don't count the temporary reference taken inside procfs seq_show */
seq_printf(m, "count:\t%ld\n", file_count(dmabuf->file) - 1);
seq_printf(m, "exp_name:\t%s\n", dmabuf->exp_name);
- mutex_lock(&dmabuf->lock);
+ dma_resv_lock(dmabuf->resv, NULL);
if (dmabuf->name)
seq_printf(m, "name:\t%s\n", dmabuf->name);
- mutex_unlock(&dmabuf->lock);
+ dma_resv_unlock(dmabuf->resv);
}
static const struct file_operations dma_buf_fops = {
@@ -525,6 +525,10 @@ struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
return ERR_PTR(-EINVAL);
}
+ if (WARN_ON(exp_info->ops->cache_sgt_mapping &&
+ exp_info->ops->dynamic_mapping))
+ return ERR_PTR(-EINVAL);
+
if (!try_module_get(exp_info->owner))
return ERR_PTR(-ENOENT);
@@ -645,10 +649,11 @@ void dma_buf_put(struct dma_buf *dmabuf)
EXPORT_SYMBOL_GPL(dma_buf_put);
/**
- * dma_buf_attach - Add the device to dma_buf's attachments list; optionally,
+ * dma_buf_dynamic_attach - Add the device to dma_buf's attachments list; optionally,
* calls attach() of dma_buf_ops to allow device-specific attach functionality
- * @dmabuf: [in] buffer to attach device to.
- * @dev: [in] device to be attached.
+ * @dmabuf: [in] buffer to attach device to.
+ * @dev: [in] device to be attached.
+ * @dynamic_mapping: [in] calling convention for map/unmap
*
* Returns struct dma_buf_attachment pointer for this attachment. Attachments
* must be cleaned up by calling dma_buf_detach().
@@ -662,8 +667,9 @@ EXPORT_SYMBOL_GPL(dma_buf_put);
* accessible to @dev, and cannot be moved to a more suitable place. This is
* indicated with the error code -EBUSY.
*/
-struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
- struct device *dev)
+struct dma_buf_attachment *
+dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
+ bool dynamic_mapping)
{
struct dma_buf_attachment *attach;
int ret;
@@ -677,6 +683,7 @@ struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
attach->dev = dev;
attach->dmabuf = dmabuf;
+ attach->dynamic_mapping = dynamic_mapping;
mutex_lock(&dmabuf->lock);
@@ -685,16 +692,64 @@ struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
if (ret)
goto err_attach;
}
+ dma_resv_lock(dmabuf->resv, NULL);
list_add(&attach->node, &dmabuf->attachments);
+ dma_resv_unlock(dmabuf->resv);
mutex_unlock(&dmabuf->lock);
+ /* When either the importer or the exporter can't handle dynamic
+ * mappings we cache the mapping here to avoid issues with the
+ * reservation object lock.
+ */
+ if (dma_buf_attachment_is_dynamic(attach) !=
+ dma_buf_is_dynamic(dmabuf)) {
+ struct sg_table *sgt;
+
+ if (dma_buf_is_dynamic(attach->dmabuf))
+ dma_resv_lock(attach->dmabuf->resv, NULL);
+
+ sgt = dmabuf->ops->map_dma_buf(attach, DMA_BIDIRECTIONAL);
+ if (!sgt)
+ sgt = ERR_PTR(-ENOMEM);
+ if (IS_ERR(sgt)) {
+ ret = PTR_ERR(sgt);
+ goto err_unlock;
+ }
+ if (dma_buf_is_dynamic(attach->dmabuf))
+ dma_resv_unlock(attach->dmabuf->resv);
+ attach->sgt = sgt;
+ attach->dir = DMA_BIDIRECTIONAL;
+ }
+
return attach;
err_attach:
kfree(attach);
mutex_unlock(&dmabuf->lock);
return ERR_PTR(ret);
+
+err_unlock:
+ if (dma_buf_is_dynamic(attach->dmabuf))
+ dma_resv_unlock(attach->dmabuf->resv);
+
+ dma_buf_detach(dmabuf, attach);
+ return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(dma_buf_dynamic_attach);
+
+/**
+ * dma_buf_attach - Wrapper for dma_buf_dynamic_attach
+ * @dmabuf: [in] buffer to attach device to.
+ * @dev: [in] device to be attached.
+ *
+ * Wrapper to call dma_buf_dynamic_attach() for drivers which still use a static
+ * mapping.
+ */
+struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
+ struct device *dev)
+{
+ return dma_buf_dynamic_attach(dmabuf, dev, false);
}
EXPORT_SYMBOL_GPL(dma_buf_attach);
@@ -711,11 +766,20 @@ void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach)
if (WARN_ON(!dmabuf || !attach))
return;
- if (attach->sgt)
+ if (attach->sgt) {
+ if (dma_buf_is_dynamic(attach->dmabuf))
+ dma_resv_lock(attach->dmabuf->resv, NULL);
+
dmabuf->ops->unmap_dma_buf(attach, attach->sgt, attach->dir);
+ if (dma_buf_is_dynamic(attach->dmabuf))
+ dma_resv_unlock(attach->dmabuf->resv);
+ }
+
mutex_lock(&dmabuf->lock);
+ dma_resv_lock(dmabuf->resv, NULL);
list_del(&attach->node);
+ dma_resv_unlock(dmabuf->resv);
if (dmabuf->ops->detach)
dmabuf->ops->detach(dmabuf, attach);
@@ -749,6 +813,9 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
if (WARN_ON(!attach || !attach->dmabuf))
return ERR_PTR(-EINVAL);
+ if (dma_buf_attachment_is_dynamic(attach))
+ dma_resv_assert_held(attach->dmabuf->resv);
+
if (attach->sgt) {
/*
* Two mappings with different directions for the same
@@ -761,6 +828,9 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
return attach->sgt;
}
+ if (dma_buf_is_dynamic(attach->dmabuf))
+ dma_resv_assert_held(attach->dmabuf->resv);
+
sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
if (!sg_table)
sg_table = ERR_PTR(-ENOMEM);
@@ -793,9 +863,15 @@ void dma_buf_unmap_attachment(struct dma_buf_attachment *attach,
if (WARN_ON(!attach || !attach->dmabuf || !sg_table))
return;
+ if (dma_buf_attachment_is_dynamic(attach))
+ dma_resv_assert_held(attach->dmabuf->resv);
+
if (attach->sgt == sg_table)
return;
+ if (dma_buf_is_dynamic(attach->dmabuf))
+ dma_resv_assert_held(attach->dmabuf->resv);
+
attach->dmabuf->ops->unmap_dma_buf(attach, sg_table, direction);
}
EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment);
@@ -1171,13 +1247,14 @@ static int dma_buf_debug_show(struct seq_file *s, void *unused)
"size", "flags", "mode", "count", "ino");
list_for_each_entry(buf_obj, &db_list.head, list_node) {
+
ret = mutex_lock_interruptible(&buf_obj->lock);
+ if (ret)
+ goto error_unlock_list;
- if (ret) {
- seq_puts(s,
- "\tERROR locking buffer object: skipping\n");
- continue;
- }
+ ret = dma_resv_lock_interruptible(buf_obj->resv, NULL);
+ if (ret)
+ goto error_unlock_buf;
seq_printf(s, "%08zu\t%08x\t%08x\t%08ld\t%s\t%08lu\t%s\n",
buf_obj->size,
@@ -1223,6 +1300,7 @@ static int dma_buf_debug_show(struct seq_file *s, void *unused)
seq_printf(s, "\t%s\n", dev_name(attach_obj->dev));
attach_count++;
}
+ dma_resv_unlock(buf_obj->resv);
seq_printf(s, "Total %d devices attached\n\n",
attach_count);
@@ -1236,6 +1314,12 @@ static int dma_buf_debug_show(struct seq_file *s, void *unused)
mutex_unlock(&db_list.lock);
return 0;
+
+error_unlock_buf:
+ mutex_unlock(&buf_obj->lock);
+error_unlock_list:
+ mutex_unlock(&db_list.lock);
+ return ret;
}
DEFINE_SHOW_ATTRIBUTE(dma_buf_debug);