linux-kernel - Re: [PATCH v4 5/9] iommu/vt-d: Don't switch off swiotlb if use direct dma

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Message-ID: <20190610155451.GU28796@char.us.oracle.com>
Date:   Mon, 10 Jun 2019 11:54:51 -0400
From:   Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:     Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     David Woodhouse <dwmw2@...radead.org>,
        Joerg Roedel <joro@...tes.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Christoph Hellwig <hch@....de>, ashok.raj@...el.com,
        jacob.jun.pan@...el.com, alan.cox@...el.com, kevin.tian@...el.com,
        mika.westerberg@...ux.intel.com, Ingo Molnar <mingo@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        pengfei.xu@...el.com, Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>,
        Jonathan Corbet <corbet@....net>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Mika Westerberg <mika.westerberg@...el.com>
Subject: Re: [PATCH v4 5/9] iommu/vt-d: Don't switch off swiotlb if use
 direct dma

On Mon, Jun 03, 2019 at 09:16:16AM +0800, Lu Baolu wrote:
> The direct dma implementation depends on swiotlb. Hence, don't
> switch of swiotlb since direct dma interfaces are used in this

s/of/off/

> driver.

But I think you really want to leave the code as is but change
the #ifdef to check for IOMMU_BOUNCE_PAGE and not CONFIG_SWIOTLB.

As one could disable IOMMU_BOUNCE_PAGE.
> 
> Cc: Ashok Raj <ashok.raj@...el.com>
> Cc: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> Cc: Kevin Tian <kevin.tian@...el.com>
> Cc: Mika Westerberg <mika.westerberg@...el.com>
> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
> ---
>  drivers/iommu/intel-iommu.c | 6 ------
>  1 file changed, 6 deletions(-)
> 
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index d5a6c8064c56..235837c50719 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -4625,9 +4625,6 @@ static int __init platform_optin_force_iommu(void)
>  		iommu_identity_mapping |= IDENTMAP_ALL;
>  
>  	dmar_disabled = 0;
> -#if defined(CONFIG_X86) && defined(CONFIG_SWIOTLB)
> -	swiotlb = 0;
> -#endif
>  	no_iommu = 0;
>  
>  	return 1;
> @@ -4765,9 +4762,6 @@ int __init intel_iommu_init(void)
>  	}
>  	up_write(&dmar_global_lock);
>  
> -#if defined(CONFIG_X86) && defined(CONFIG_SWIOTLB)
> -	swiotlb = 0;
> -#endif
>  	dma_ops = &intel_dma_ops;
>  
>  	init_iommu_pm_ops();
> -- 
> 2.17.1
>