linux-kernel - Re: [PATCH 1/3] iommu/vt-d: Remove redundant IOTLB flush

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Message-ID: <5aff3f99-9f8b-4d61-8c88-8b22a8f7f722@linux.intel.com>
Date:   Wed, 25 Mar 2020 08:48:51 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc:     baolu.lu@...ux.intel.com, LKML <linux-kernel@...r.kernel.org>,
        iommu@...ts.linux-foundation.org, Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Raj Ashok <ashok.raj@...el.com>, Yi Liu <yi.l.liu@...el.com>
Subject: Re: [PATCH 1/3] iommu/vt-d: Remove redundant IOTLB flush

On 2020/3/24 23:31, Jacob Pan wrote:
> On Sat, 21 Mar 2020 09:32:45 +0800
> Lu Baolu<baolu.lu@...ux.intel.com>  wrote:
> 
>> On 2020/3/21 0:20, Jacob Pan wrote:
>>> On Fri, 20 Mar 2020 21:45:26 +0800
>>> Lu Baolu<baolu.lu@...ux.intel.com>  wrote:
>>>    
>>>> On 2020/3/20 12:32, Jacob Pan wrote:
>>>>> IOTLB flush already included in the PASID tear down process. There
>>>>> is no need to flush again.
>>>> It seems that intel_pasid_tear_down_entry() doesn't flush the pasid
>>>> based device TLB?
>>>>   
>>> I saw this code in intel_pasid_tear_down_entry(). Isn't the last
>>> line flush the devtlb? Not in guest of course since the passdown
>>> tlb flush is inclusive.
>>>
>>> 	pasid_cache_invalidation_with_pasid(iommu, did, pasid);
>>> 	iotlb_invalidation_with_pasid(iommu, did, pasid);
>>>
>>> 	/* Device IOTLB doesn't need to be flushed in caching mode.
>>> */ if (!cap_caching_mode(iommu->cap))
>>> 		devtlb_invalidation_with_pasid(iommu, dev, pasid);
>>>    
>> But devtlb_invalidation_with_pasid() doesn't do the right thing, it
>> flushes the device tlb, instead of pasid-based device tlb.
>>
> Hmm, you are right. But the function name is misleading, pasid argument
> is not used, is there a reason why?
> This is used for PASID based device IOTLB flush, right?
> 

Yes. I will fix and put your patch after it.

Best regards,
baolu