linux-kernel - Re: [PATCH 09/11] swiotlb-xen: simplify cache maintainance

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Message-ID: <e4f9b393-2631-57cd-f42f-3581e75ab9a3@oracle.com>
Date:   Fri, 6 Sep 2019 09:52:12 -0400
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     Christoph Hellwig <hch@....de>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        gross@...e.com
Cc:     x86@...nel.org, linux-arm-kernel@...ts.infradead.org,
        xen-devel@...ts.xenproject.org, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 09/11] swiotlb-xen: simplify cache maintainance

On 9/5/19 7:34 AM, Christoph Hellwig wrote:
> diff --git a/include/xen/swiotlb-xen.h b/include/xen/swiotlb-xen.h
> index 5e4b83f83dbc..d71380f6ed0b 100644
> --- a/include/xen/swiotlb-xen.h
> +++ b/include/xen/swiotlb-xen.h
> @@ -4,6 +4,11 @@
>  
>  #include <linux/swiotlb.h>
>  
> +void xen_dma_sync_for_cpu(struct device *dev, dma_addr_t handle,
> +		phys_addr_t paddr, size_t size, enum dma_data_direction dir);
> +void xen_dma_sync_for_device(struct device *dev, dma_addr_t handle,
> +		phys_addr_t paddr, size_t size, enum dma_data_direction dir);
> +
>  extern int xen_swiotlb_init(int verbose, bool early);
>  extern const struct dma_map_ops xen_swiotlb_dma_ops;


We need nop definitions of these two for x86.

Everything builds now but that's probably because the calls are under
'if (!dev_is_dma_coherent(dev))' which is always false so compiler
optimized is out. I don't think we should rely on that.

-boris