xiaomi-sm8450/android_kernel_xiaomi_sm8450
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

xen/arm: reimplement xen_dma_unmap_page & friends

Browse Source 
xen_dma_unmap_page, xen_dma_sync_single_for_cpu and
xen_dma_sync_single_for_device are currently implemented by calling into
the corresponding generic ARM implementation of these functions. In
order to do this, firstly the dma_addr_t handle, that on Xen is a
machine address, needs to be translated into a physical address.  The
operation is expensive and inaccurate, given that a single machine
address can correspond to multiple physical addresses in one domain,
because the same page can be granted multiple times by the frontend.

To avoid this problem, we introduce a Xen specific implementation of
xen_dma_unmap_page, xen_dma_sync_single_for_cpu and
xen_dma_sync_single_for_device, that can operate on machine addresses
directly.

The new implementation relies on the fact that the hypervisor creates a
second p2m mapping of any grant pages at physical address == machine
address of the page for dom0. Therefore we can access memory at physical
address == dma_addr_r handle and perform the cache flushing there. Some
cache maintenance operations require a virtual address. Instead of using
ioremap_cache, that is not safe in interrupt context, we allocate a
per-cpu PAGE_KERNEL scratch page and we manually update the pte for it.

arm64 doesn't need cache maintenance operations on unmap for now.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Tested-by: Denis Schneider <v1ne2go@gmail.com>
This commit is contained in:
Stefano Stabellini
2014-09-10 22:49:41 +00:00
parent 5ebc77de83
commit 340720be32
3 changed files with 210 additions and 19 deletions
Download Patch File Download Diff File Expand all files Collapse all files

25
arch/arm/include/asm/xen/page-coherent.h
View File

@@ -26,25 +26,14 @@ static inline void xen_dma_map_page(struct device *hwdev, struct page *page,
__generic_dma_ops(hwdev)->map_page(hwdev, page, offset, size, dir, attrs);
}
static inline void xen_dma_unmap_page(struct device *hwdev, dma_addr_t handle,
void xen_dma_unmap_page(struct device *hwdev, dma_addr_t handle,
size_t size, enum dma_data_direction dir,
struct dma_attrs *attrs)
{
if (__generic_dma_ops(hwdev)->unmap_page)
__generic_dma_ops(hwdev)->unmap_page(hwdev, handle, size, dir, attrs);
}
struct dma_attrs *attrs);
static inline void xen_dma_sync_single_for_cpu(struct device *hwdev,
dma_addr_t handle, size_t size, enum dma_data_direction dir)
{
if (__generic_dma_ops(hwdev)->sync_single_for_cpu)
__generic_dma_ops(hwdev)->sync_single_for_cpu(hwdev, handle, size, dir);
}
void xen_dma_sync_single_for_cpu(struct device *hwdev,
dma_addr_t handle, size_t size, enum dma_data_direction dir);
void xen_dma_sync_single_for_device(struct device *hwdev,
dma_addr_t handle, size_t size, enum dma_data_direction dir);
static inline void xen_dma_sync_single_for_device(struct device *hwdev,
dma_addr_t handle, size_t size, enum dma_data_direction dir)
{
if (__generic_dma_ops(hwdev)->sync_single_for_device)
__generic_dma_ops(hwdev)->sync_single_for_device(hwdev, handle, size, dir);
}
#endif /* _ASM_ARM_XEN_PAGE_COHERENT_H */