linux-kernel - Re: [PATCH] intel-iommu: Don't be too aggressive when clearing one context entry

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Date:   Wed, 30 Aug 2017 08:50:25 -0700
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     Filippo Sironi via iommu <iommu@...ts.linux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, Filippo Sironi <sironi@...zon.de>,
        David Woodhouse <dwmw2@...radead.org>,
        David Woodhouse <dwmw@...zon.co.uk>,
        jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH] intel-iommu: Don't be too aggressive when clearing one
 context entry

On Mon, 28 Aug 2017 16:16:29 +0200
Filippo Sironi via iommu <iommu@...ts.linux-foundation.org> wrote:

> Previously, we were invalidating context cache and IOTLB globally when
> clearing one context entry.  This is a tad too aggressive.
> Invalidate the context cache and IOTLB for the interested device only.
> 
> Signed-off-by: Filippo Sironi <sironi@...zon.de>
> Cc: David Woodhouse <dwmw@...zon.co.uk>
> Cc: David Woodhouse <dwmw2@...radead.org>
> Cc: Joerg Roedel <joro@...tes.org>
> Cc: iommu@...ts.linux-foundation.org
> Cc: linux-kernel@...r.kernel.org
> ---
>  drivers/iommu/intel-iommu.c | 25 ++++++++++++++++++++++---
>  1 file changed, 22 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index 3e8636f1220e..4bf3e59b0929 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -2351,13 +2351,32 @@ static inline int domain_pfn_mapping(struct
> dmar_domain *domain, unsigned long i 
>  static void domain_context_clear_one(struct intel_iommu *iommu, u8
> bus, u8 devfn) {
> +	unsigned long flags;
> +	struct context_entry *context;
> +	u16 did_old;
> +
>  	if (!iommu)
>  		return;
>  
> +	spin_lock_irqsave(&iommu->lock, flags);
> +	context = iommu_context_addr(iommu, bus, devfn, 0);
> +	if (!context) {
> +		spin_unlock_irqrestore(&iommu->lock, flags);
> +		return;
> +	}
perhaps check with device_context_mapped()?

> +	did_old = context_domain_id(context);
> +	spin_unlock_irqrestore(&iommu->lock, flags);
>  	clear_context_table(iommu, bus, devfn);
> -	iommu->flush.flush_context(iommu, 0, 0, 0,
> -					   DMA_CCMD_GLOBAL_INVL);
> -	iommu->flush.flush_iotlb(iommu, 0, 0, 0,
> DMA_TLB_GLOBAL_FLUSH);
> +	iommu->flush.flush_context(iommu,
> +				   did_old,
> +				   (((u16)bus) << 8) | devfn,
> +				   DMA_CCMD_MASK_NOBIT,
> +				   DMA_CCMD_DEVICE_INVL);
> +	iommu->flush.flush_iotlb(iommu,
> +				 did_old,
> +				 0,
> +				 0,
> +				 DMA_TLB_DSI_FLUSH);
>  }
>  
>  static inline void unlink_domain_info(struct device_domain_info
> *info)

[Jacob Pan]