linux-kernel - Re: [PATCH 10/10] xen/arm: call dma_to_phys on the dma_addr_t parameter of dma_cache

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Date:   Thu, 21 May 2020 09:25:57 +0100
From:   Julien Grall <julien@....org>
To:     Stefano Stabellini <sstabellini@...nel.org>, jgross@...e.com,
        boris.ostrovsky@...cle.com, konrad.wilk@...cle.com
Cc:     xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
        Stefano Stabellini <stefano.stabellini@...inx.com>
Subject: Re: [PATCH 10/10] xen/arm: call dma_to_phys on the dma_addr_t
 parameter of dma_cache_maint



On 21/05/2020 00:45, Stefano Stabellini wrote:
> From: Stefano Stabellini <stefano.stabellini@...inx.com>
> 
> Add a struct device* parameter to dma_cache_maint.
> 
> Translate the dma_addr_t parameter of dma_cache_maint by calling
> dma_to_phys. Do it for the first page and all the following pages, in
> case of multipage handling.

The term 'page' is confusing here. Are we referring to Xen page or Linux 
page?

Also, same as patch #8 and #9 regarding the commit message.

> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@...inx.com>
> ---
>   arch/arm/xen/mm.c | 15 +++++++++------
>   1 file changed, 9 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm/xen/mm.c b/arch/arm/xen/mm.c
> index 7639251bcc79..6ddf3b3c1ab5 100644
> --- a/arch/arm/xen/mm.c
> +++ b/arch/arm/xen/mm.c
> @@ -43,15 +43,18 @@ unsigned long xen_get_swiotlb_free_pages(unsigned int order)
>   static bool hypercall_cflush = false;
>   
>   /* buffers in highmem or foreign pages cannot cross page boundaries */
> -static void dma_cache_maint(dma_addr_t handle, size_t size, u32 op)
> +static void dma_cache_maint(struct device *dev, dma_addr_t handle,
> +			    size_t size, u32 op)
>   {
>   	struct gnttab_cache_flush cflush;
>   
> -	cflush.a.dev_bus_addr = handle & XEN_PAGE_MASK;
>   	cflush.offset = xen_offset_in_page(handle);
>   	cflush.op = op;
> +	handle &= XEN_PAGE_MASK;
>   
>   	do {
> +		cflush.a.dev_bus_addr = dma_to_phys(dev, handle);
> +
>   		if (size + cflush.offset > XEN_PAGE_SIZE)
>   			cflush.length = XEN_PAGE_SIZE - cflush.offset;
>   		else
> @@ -60,7 +63,7 @@ static void dma_cache_maint(dma_addr_t handle, size_t size, u32 op)
>   		HYPERVISOR_grant_table_op(GNTTABOP_cache_flush, &cflush, 1);
>   
>   		cflush.offset = 0;
> -		cflush.a.dev_bus_addr += cflush.length;
> +		handle += cflush.length;
>   		size -= cflush.length;
>   	} while (size);
>   }
> @@ -79,7 +82,7 @@ void xen_dma_sync_for_cpu(struct device *dev, dma_addr_t handle,
>   	if (pfn_valid(PFN_DOWN(dma_to_phys(dev, handle))))
>   		arch_sync_dma_for_cpu(paddr, size, dir);
>   	else if (dir != DMA_TO_DEVICE)
> -		dma_cache_maint(handle, size, GNTTAB_CACHE_INVAL);
> +		dma_cache_maint(dev, handle, size, GNTTAB_CACHE_INVAL);
>   }
>   
>   void xen_dma_sync_for_device(struct device *dev, dma_addr_t handle,
> @@ -89,9 +92,9 @@ void xen_dma_sync_for_device(struct device *dev, dma_addr_t handle,
>   	if (pfn_valid(PFN_DOWN(dma_to_phys(dev, handle))))
>   		arch_sync_dma_for_device(paddr, size, dir);
>   	else if (dir == DMA_FROM_DEVICE)
> -		dma_cache_maint(handle, size, GNTTAB_CACHE_INVAL);
> +		dma_cache_maint(dev, handle, size, GNTTAB_CACHE_INVAL);
>   	else
> -		dma_cache_maint(handle, size, GNTTAB_CACHE_CLEAN);
> +		dma_cache_maint(dev, handle, size, GNTTAB_CACHE_CLEAN);
>   }
>   
>   bool xen_arch_need_swiotlb(struct device *dev,
> 

Cheers,

-- 
Julien Grall