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

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Date:   Thu, 31 Aug 2017 08:41:25 +0000
From:   "Sironi, Filippo" <sironi@...zon.de>
To:     Joerg Roedel <joro@...tes.org>
CC:     "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Woodhouse, David" <dwmw@...zon.co.uk>,
        David Woodhouse <dwmw2@...radead.org>
Subject: Re: [PATCH] intel-iommu: Don't be too aggressive when clearing one
 context entry

Hi Joerg,

> On 30. Aug 2017, at 15:31, Joerg Roedel <joro@...tes.org> wrote:
> 
> Hi Filippo,
> 
> please change the subject to:
> 
> 	iommu/vt-d: Don't be too aggressive when clearing one context entry
> 
> to follow the convention used in the iommu-tree. Another comment below.

Will do.

> On Mon, Aug 28, 2017 at 04:16:29PM +0200, Filippo Sironi wrote:
>> 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;
>> +	}
>> +	did_old = context_domain_id(context);
>> +	spin_unlock_irqrestore(&iommu->lock, flags);
>> 	clear_context_table(iommu, bus, devfn);
> 
> This function is the only caller of clear_context_table(), which does
> similar things (like fetching the context-entry) as you are adding
> above.
> 
> So you can either make clear_context_table() return the old domain-id
> so that you don't need to do it here, or you get rid of the function
> entirely and add the context_clear_entry() and __iommu_flush_cache()
> calls into this code-path.
> 
> Regards,
> 
> 	Joerg

I went for merging domain_context_clear_one() with context_clear_one().

Regards,
Filippo


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