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Message-Id: <20250107142719.179636-2-yilun.xu@linux.intel.com>
Date: Tue, 7 Jan 2025 22:27:08 +0800
From: Xu Yilun <yilun.xu@...ux.intel.com>
To: kvm@...r.kernel.org,
dri-devel@...ts.freedesktop.org,
linux-media@...r.kernel.org,
linaro-mm-sig@...ts.linaro.org,
sumit.semwal@...aro.org,
christian.koenig@....com,
pbonzini@...hat.com,
seanjc@...gle.com,
alex.williamson@...hat.com,
jgg@...dia.com,
vivek.kasireddy@...el.com,
dan.j.williams@...el.com,
aik@....com
Cc: yilun.xu@...el.com,
yilun.xu@...ux.intel.com,
linux-coco@...ts.linux.dev,
linux-kernel@...r.kernel.org,
lukas@...ner.de,
yan.y.zhao@...el.com,
daniel.vetter@...ll.ch,
leon@...nel.org,
baolu.lu@...ux.intel.com,
zhenzhong.duan@...el.com,
tao1.su@...el.com
Subject: [RFC PATCH 01/12] dma-buf: Introduce dma_buf_get_pfn_unlocked() kAPI
Introduce a new API for dma-buf importer, also add a dma_buf_ops
callback for dma-buf exporter. This API is for subsystem importers who
map the dma-buf to some user defined address space, e.g. for IOMMUFD to
map the dma-buf to userspace IOVA via IOMMU page table, or for KVM to
map the dma-buf to GPA via KVM MMU (e.g. EPT).
Currently dma-buf is only used to get DMA address for device's default
domain by using kernel DMA APIs. But for these new use-cases, importers
only need the pfn of the dma-buf resource to build their own mapping
tables. So the map_dma_buf() callback is not mandatory for exporters
anymore. Also the importers could choose not to provide
struct device *dev on dma_buf_attach() if they don't call
dma_buf_map_attachment().
Like dma_buf_map_attachment(), the importer should firstly call
dma_buf_attach/dynamic_attach() then call dma_buf_get_pfn_unlocked().
If the importer choose to do dynamic attach, it also should handle the
dma-buf move notification.
Only the unlocked version of dma_buf_get_pfn is implemented for now,
just because no locked version is used for now.
Signed-off-by: Xu Yilun <yilun.xu@...ux.intel.com>
---
IIUC, Only get_pfn() is needed but no put_pfn(). The whole dma-buf is
de/referenced at dma-buf attach/detach time.
Specifically, for static attachment, the exporter should always make
memory resource available/pinned on first dma_buf_attach(), and
release/unpin memory resource on last dma_buf_detach(). For dynamic
attachment, the exporter could populate & invalidate the memory
resource at any time, it's OK as long as the importers follow dma-buf
move notification. So no pinning is needed for get_pfn() and no
put_pfn() is needed.
---
drivers/dma-buf/dma-buf.c | 90 +++++++++++++++++++++++++++++++--------
include/linux/dma-buf.h | 13 ++++++
2 files changed, 86 insertions(+), 17 deletions(-)
diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 7eeee3a38202..83d1448b6dcc 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -630,10 +630,10 @@ struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
size_t alloc_size = sizeof(struct dma_buf);
int ret;
- if (WARN_ON(!exp_info->priv || !exp_info->ops
- || !exp_info->ops->map_dma_buf
- || !exp_info->ops->unmap_dma_buf
- || !exp_info->ops->release))
+ if (WARN_ON(!exp_info->priv || !exp_info->ops ||
+ (!!exp_info->ops->map_dma_buf != !!exp_info->ops->unmap_dma_buf) ||
+ (!exp_info->ops->map_dma_buf && !exp_info->ops->get_pfn) ||
+ !exp_info->ops->release))
return ERR_PTR(-EINVAL);
if (WARN_ON(exp_info->ops->cache_sgt_mapping &&
@@ -909,7 +909,10 @@ dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
struct dma_buf_attachment *attach;
int ret;
- if (WARN_ON(!dmabuf || !dev))
+ if (WARN_ON(!dmabuf))
+ return ERR_PTR(-EINVAL);
+
+ if (WARN_ON(dmabuf->ops->map_dma_buf && !dev))
return ERR_PTR(-EINVAL);
if (WARN_ON(importer_ops && !importer_ops->move_notify))
@@ -941,7 +944,7 @@ dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
*/
if (dma_buf_attachment_is_dynamic(attach) !=
dma_buf_is_dynamic(dmabuf)) {
- struct sg_table *sgt;
+ struct sg_table *sgt = NULL;
dma_resv_lock(attach->dmabuf->resv, NULL);
if (dma_buf_is_dynamic(attach->dmabuf)) {
@@ -950,13 +953,16 @@ dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
goto err_unlock;
}
- sgt = __map_dma_buf(attach, DMA_BIDIRECTIONAL);
- if (!sgt)
- sgt = ERR_PTR(-ENOMEM);
- if (IS_ERR(sgt)) {
- ret = PTR_ERR(sgt);
- goto err_unpin;
+ if (dmabuf->ops->map_dma_buf) {
+ sgt = __map_dma_buf(attach, DMA_BIDIRECTIONAL);
+ if (!sgt)
+ sgt = ERR_PTR(-ENOMEM);
+ if (IS_ERR(sgt)) {
+ ret = PTR_ERR(sgt);
+ goto err_unpin;
+ }
}
+
dma_resv_unlock(attach->dmabuf->resv);
attach->sgt = sgt;
attach->dir = DMA_BIDIRECTIONAL;
@@ -1119,7 +1125,8 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
might_sleep();
- if (WARN_ON(!attach || !attach->dmabuf))
+ if (WARN_ON(!attach || !attach->dmabuf ||
+ !attach->dmabuf->ops->map_dma_buf))
return ERR_PTR(-EINVAL);
dma_resv_assert_held(attach->dmabuf->resv);
@@ -1195,7 +1202,8 @@ dma_buf_map_attachment_unlocked(struct dma_buf_attachment *attach,
might_sleep();
- if (WARN_ON(!attach || !attach->dmabuf))
+ if (WARN_ON(!attach || !attach->dmabuf ||
+ !attach->dmabuf->ops->map_dma_buf))
return ERR_PTR(-EINVAL);
dma_resv_lock(attach->dmabuf->resv, NULL);
@@ -1222,7 +1230,8 @@ void dma_buf_unmap_attachment(struct dma_buf_attachment *attach,
{
might_sleep();
- if (WARN_ON(!attach || !attach->dmabuf || !sg_table))
+ if (WARN_ON(!attach || !attach->dmabuf ||
+ !attach->dmabuf->ops->unmap_dma_buf || !sg_table))
return;
dma_resv_assert_held(attach->dmabuf->resv);
@@ -1254,7 +1263,8 @@ void dma_buf_unmap_attachment_unlocked(struct dma_buf_attachment *attach,
{
might_sleep();
- if (WARN_ON(!attach || !attach->dmabuf || !sg_table))
+ if (WARN_ON(!attach || !attach->dmabuf ||
+ !attach->dmabuf->ops->unmap_dma_buf || !sg_table))
return;
dma_resv_lock(attach->dmabuf->resv, NULL);
@@ -1263,6 +1273,52 @@ void dma_buf_unmap_attachment_unlocked(struct dma_buf_attachment *attach,
}
EXPORT_SYMBOL_NS_GPL(dma_buf_unmap_attachment_unlocked, "DMA_BUF");
+/**
+ * dma_buf_get_pfn_unlocked -
+ * @attach: [in] attachment to get pfn from
+ * @pgoff: [in] page offset of the buffer against the start of dma_buf
+ * @pfn: [out] returns the pfn of the buffer
+ * @max_order [out] returns the max mapping order of the buffer
+ */
+int dma_buf_get_pfn_unlocked(struct dma_buf_attachment *attach,
+ pgoff_t pgoff, u64 *pfn, int *max_order)
+{
+ struct dma_buf *dmabuf = attach->dmabuf;
+ int ret;
+
+ if (WARN_ON(!attach || !attach->dmabuf ||
+ !attach->dmabuf->ops->get_pfn))
+ return -EINVAL;
+
+ /*
+ * Open:
+ *
+ * When dma_buf is dynamic but dma_buf move is disabled, the buffer
+ * should be pinned before use, See dma_buf_map_attachment() for
+ * reference.
+ *
+ * But for now no pin is intended inside dma_buf_get_pfn(), otherwise
+ * need another API to unpin the dma_buf. So just fail out this case.
+ */
+ if (dma_buf_is_dynamic(attach->dmabuf) &&
+ !IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY))
+ return -ENOENT;
+
+ dma_resv_lock(attach->dmabuf->resv, NULL);
+ ret = dmabuf->ops->get_pfn(attach, pgoff, pfn, max_order);
+ /*
+ * Open:
+ *
+ * Is dma_resv_wait_timeout() needed? I assume no. The DMA buffer
+ * content synchronization could be done when the buffer is to be
+ * mapped by importer.
+ */
+ dma_resv_unlock(attach->dmabuf->resv);
+
+ return ret;
+}
+EXPORT_SYMBOL_NS_GPL(dma_buf_get_pfn_unlocked, "DMA_BUF");
+
/**
* dma_buf_move_notify - notify attachments that DMA-buf is moving
*
@@ -1662,7 +1718,7 @@ static int dma_buf_debug_show(struct seq_file *s, void *unused)
attach_count = 0;
list_for_each_entry(attach_obj, &buf_obj->attachments, node) {
- seq_printf(s, "\t%s\n", dev_name(attach_obj->dev));
+ seq_printf(s, "\t%s\n", attach_obj->dev ? dev_name(attach_obj->dev) : NULL);
attach_count++;
}
dma_resv_unlock(buf_obj->resv);
diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
index 36216d28d8bd..b16183edfb3a 100644
--- a/include/linux/dma-buf.h
+++ b/include/linux/dma-buf.h
@@ -194,6 +194,17 @@ struct dma_buf_ops {
* if the call would block.
*/
+ /**
+ * @get_pfn:
+ *
+ * This is called by dma_buf_get_pfn(). It is used to get the pfn
+ * of the buffer positioned by the page offset against the start of
+ * the dma_buf. It can only be called if @attach has been called
+ * successfully.
+ */
+ int (*get_pfn)(struct dma_buf_attachment *attach, pgoff_t pgoff,
+ u64 *pfn, int *max_order);
+
/**
* @release:
*
@@ -629,6 +640,8 @@ dma_buf_map_attachment_unlocked(struct dma_buf_attachment *attach,
void dma_buf_unmap_attachment_unlocked(struct dma_buf_attachment *attach,
struct sg_table *sg_table,
enum dma_data_direction direction);
+int dma_buf_get_pfn_unlocked(struct dma_buf_attachment *attach,
+ pgoff_t pgoff, u64 *pfn, int *max_order);
int dma_buf_mmap(struct dma_buf *, struct vm_area_struct *,
unsigned long);
--
2.25.1
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