Re: [PATCH 06/11] swiotlb-xen: always use dma-direct helpers to alloc coherent pages

Stefano Stabellini
2019-08-29T22:48:12Z

+ Boris, Juergen

On Mon, 26 Aug 2019, Christoph Hellwig wrote:
> x86 currently calls alloc_pages, but using dma-direct works as well
> there, with the added benefit of using the CMA pool if available.
> The biggest advantage is of course to remove a pointless bit of
> architecture specific code.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> arch/x86/include/asm/xen/page-coherent.h | 16 ----------------
> drivers/xen/swiotlb-xen.c | 7 +++----
> include/xen/arm/page-coherent.h | 12 ------------
> 3 files changed, 3 insertions(+), 32 deletions(-)
>
> diff --git a/arch/x86/include/asm/xen/page-coherent.h b/arch/x86/include/asm/xen/page-coherent.h
> index 116777e7f387..8ee33c5edded 100644
> --- a/arch/x86/include/asm/xen/page-coherent.h
> +++ b/arch/x86/include/asm/xen/page-coherent.h
> @@ -5,22 +5,6 @@
> #include <asm/page.h>
> #include <linux/dma-mapping.h>
>
> -static inline void *xen_alloc_coherent_pages(struct device *hwdev, size_t size,
> - dma_addr_t *dma_handle, gfp_t flags,
> - unsigned long attrs)
> -{
> - void *vstart = (void*)__get_free_pages(flags, get_order(size));
> - *dma_handle = virt_to_phys(vstart);

This is where we need Boris and Juergen's opinion. From an ARM POV it
looks OK.

> - return vstart;
> -}
> -
> -static inline void xen_free_coherent_pages(struct device *hwdev, size_t size,
> - void *cpu_addr, dma_addr_t dma_handle,
> - unsigned long attrs)
> -{
> - free_pages((unsigned long) cpu_addr, get_order(size));
> -}
> -
> static inline void xen_dma_map_page(struct device *hwdev, struct page *page,
> dma_addr_t dev_addr, unsigned long offset, size_t size,
> enum dma_data_direction dir, unsigned long attrs) { }
> diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
> index b8808677ae1d..f9dd4cb6e4b3 100644
> --- a/drivers/xen/swiotlb-xen.c
> +++ b/drivers/xen/swiotlb-xen.c
> @@ -299,8 +299,7 @@ xen_swiotlb_alloc_coherent(struct device *hwdev, size_t size,
> * address. In fact on ARM virt_to_phys only works for kernel direct
> * mapped RAM memory. Also see comment below.
> */
> - ret = xen_alloc_coherent_pages(hwdev, size, dma_handle, flags, attrs);
> -
> + ret = dma_direct_alloc(hwdev, size, dma_handle, flags, attrs);
> if (!ret)
> return ret;
>
> @@ -319,7 +318,7 @@ xen_swiotlb_alloc_coherent(struct device *hwdev, size_t size,
> else {
> if (xen_create_contiguous_region(phys, order,
> fls64(dma_mask), dma_handle) != 0) {
> - xen_free_coherent_pages(hwdev, size, ret, (dma_addr_t)phys, attrs);
> + dma_direct_free(hwdev, size, ret, (dma_addr_t)phys, attrs);
> return NULL;
> }
> SetPageXenRemapped(virt_to_page(ret));
> @@ -351,7 +350,7 @@ xen_swiotlb_free_coherent(struct device *hwdev, size_t size, void *vaddr,
> TestClearPageXenRemapped(virt_to_page(vaddr)))
> xen_destroy_contiguous_region(phys, order);
>
> - xen_free_coherent_pages(hwdev, size, vaddr, (dma_addr_t)phys, attrs);
> + dma_direct_free(hwdev, size, vaddr, (dma_addr_t)phys, attrs);
> }
>
> /*
> diff --git a/include/xen/arm/page-coherent.h b/include/xen/arm/page-coherent.h
> index a840d6949a87..0e244f4fec1a 100644
> --- a/include/xen/arm/page-coherent.h
> +++ b/include/xen/arm/page-coherent.h
> @@ -16,18 +16,6 @@ void __xen_dma_sync_single_for_cpu(struct device *hwdev,
> 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_alloc_coherent_pages(struct device *hwdev, size_t size,
> - dma_addr_t *dma_handle, gfp_t flags, unsigned long attrs)
> -{
> - return dma_direct_alloc(hwdev, size, dma_handle, flags, attrs);
> -}
> -
> -static inline void xen_free_coherent_pages(struct device *hwdev, size_t size,
> - void *cpu_addr, dma_addr_t dma_handle, unsigned long attrs)
> -{
> - dma_direct_free(hwdev, size, cpu_addr, dma_handle, 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)
> {
> --
> 2.20.1
>