From: Lu Baolu <baolu.lu@linux.intel.com>
To: "Tian, Kevin" <kevin.tian@intel.com>, Christoph Hellwig <hch@lst.de>
Cc: "Raj, Ashok" <ashok.raj@intel.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"iommu@lists.linux-foundation.org"
<iommu@lists.linux-foundation.org>,
Jason Gunthorpe <jgg@nvidia.com>,
Robin Murphy <robin.murphy@arm.com>
Subject: Re: [PATCH v2 09/11] iommu/vt-d: Remove commented code
Date: Wed, 16 Feb 2022 15:11:15 +0800 [thread overview]
Message-ID: <fad3abe8-f69f-1339-7bca-e0283f9182d5@linux.intel.com> (raw)
In-Reply-To: <BN9PR11MB527698691A1DF10EEB514AA08C359@BN9PR11MB5276.namprd11.prod.outlook.com>
On 2/16/22 11:45 AM, Tian, Kevin wrote:
>> From: Christoph Hellwig<hch@lst.de>
>> Sent: Monday, February 14, 2022 3:34 PM
>>
>> On Mon, Feb 14, 2022 at 10:57:02AM +0800, Lu Baolu wrote:
>>> This removes unnecessary commented code.
>> Removing dead code is always good:
>>
>> Reviewed-by: Christoph Hellwig<hch@lst.de>
>>
>> But someone might really want to take a look if draining makes sense here
>> or not.
> Looks that dead code has been there since intel-iommu driver was
> firstly introduced in 2007. I don't know whether we can dig out
> the reason (Baolu, can you have a check?) why it's only special
> cased for read draining but not write draining. I cannot find any
> such recommendation from VT-d spec.
Emm, I have no idea either. Let me check it with the architecture
experts.
>
> Looking at VT-d spec it stated that since VT-d major version 2
> drain is conducted automatically by hardware and above flags
> are essentially ignored.
>
> Given that possibly a safer option is to always set read/write
> draining flags before version 2 and skip it after.
Best regards,
baolu
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WARNING: multiple messages have this Message-ID (diff)
From: Lu Baolu <baolu.lu@linux.intel.com>
To: "Tian, Kevin" <kevin.tian@intel.com>, Christoph Hellwig <hch@lst.de>
Cc: baolu.lu@linux.intel.com, Joerg Roedel <joro@8bytes.org>,
"Raj, Ashok" <ashok.raj@intel.com>,
"Liu, Yi L" <yi.l.liu@intel.com>,
Jacob Pan <jacob.jun.pan@linux.intel.com>,
Robin Murphy <robin.murphy@arm.com>,
Jason Gunthorpe <jgg@nvidia.com>,
"iommu@lists.linux-foundation.org"
<iommu@lists.linux-foundation.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 09/11] iommu/vt-d: Remove commented code
Date: Wed, 16 Feb 2022 15:11:15 +0800 [thread overview]
Message-ID: <fad3abe8-f69f-1339-7bca-e0283f9182d5@linux.intel.com> (raw)
In-Reply-To: <BN9PR11MB527698691A1DF10EEB514AA08C359@BN9PR11MB5276.namprd11.prod.outlook.com>
On 2/16/22 11:45 AM, Tian, Kevin wrote:
>> From: Christoph Hellwig<hch@lst.de>
>> Sent: Monday, February 14, 2022 3:34 PM
>>
>> On Mon, Feb 14, 2022 at 10:57:02AM +0800, Lu Baolu wrote:
>>> This removes unnecessary commented code.
>> Removing dead code is always good:
>>
>> Reviewed-by: Christoph Hellwig<hch@lst.de>
>>
>> But someone might really want to take a look if draining makes sense here
>> or not.
> Looks that dead code has been there since intel-iommu driver was
> firstly introduced in 2007. I don't know whether we can dig out
> the reason (Baolu, can you have a check?) why it's only special
> cased for read draining but not write draining. I cannot find any
> such recommendation from VT-d spec.
Emm, I have no idea either. Let me check it with the architecture
experts.
>
> Looking at VT-d spec it stated that since VT-d major version 2
> drain is conducted automatically by hardware and above flags
> are essentially ignored.
>
> Given that possibly a safer option is to always set read/write
> draining flags before version 2 and skip it after.
Best regards,
baolu
next prev parent reply other threads:[~2022-02-16 7:12 UTC|newest]
Thread overview: 72+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-14 2:56 [PATCH v2 00/11] iommu/vt-d: Some Intel IOMMU cleanups Lu Baolu
2022-02-14 2:56 ` Lu Baolu
2022-02-14 2:56 ` [PATCH v2 01/11] iommu/vt-d: Remove intel_iommu::domains Lu Baolu
2022-02-14 2:56 ` Lu Baolu
2022-02-24 12:58 ` Jason Gunthorpe via iommu
2022-02-24 12:58 ` Jason Gunthorpe
2022-02-14 2:56 ` [PATCH v2 02/11] iommu/vt-d: Remove finding domain in dmar_insert_one_dev_info() Lu Baolu
2022-02-14 2:56 ` Lu Baolu
2022-02-24 12:59 ` Jason Gunthorpe via iommu
2022-02-24 12:59 ` Jason Gunthorpe
2022-02-14 2:56 ` [PATCH v2 03/11] iommu/vt-d: Remove iova_cache_get/put() Lu Baolu
2022-02-14 2:56 ` Lu Baolu
2022-02-24 13:00 ` Jason Gunthorpe via iommu
2022-02-24 13:00 ` Jason Gunthorpe
2022-02-14 2:56 ` [PATCH v2 04/11] iommu/vt-d: Remove domain and devinfo mempool Lu Baolu
2022-02-14 2:56 ` Lu Baolu
2022-02-24 13:01 ` Jason Gunthorpe via iommu
2022-02-24 13:01 ` Jason Gunthorpe
2022-02-14 2:56 ` [PATCH v2 05/11] iommu/vt-d: Remove DEFER_DEVICE_DOMAIN_INFO Lu Baolu
2022-02-14 2:56 ` Lu Baolu
2022-02-14 7:31 ` Christoph Hellwig
2022-02-14 7:31 ` Christoph Hellwig
2022-02-24 13:04 ` Jason Gunthorpe via iommu
2022-02-24 13:04 ` Jason Gunthorpe
2022-02-25 1:55 ` Lu Baolu
2022-02-25 1:55 ` Lu Baolu
2022-02-14 2:56 ` [PATCH v2 06/11] iommu/vt-d: Remove unnecessary includes Lu Baolu
2022-02-14 2:56 ` Lu Baolu
2022-02-14 7:32 ` Christoph Hellwig
2022-02-14 7:32 ` Christoph Hellwig
2022-02-24 13:05 ` Jason Gunthorpe via iommu
2022-02-24 13:05 ` Jason Gunthorpe
2022-02-25 1:56 ` Lu Baolu
2022-02-25 1:56 ` Lu Baolu
2022-02-14 2:57 ` [PATCH v2 07/11] iommu/vt-d: Remove unnecessary prototypes Lu Baolu
2022-02-14 2:57 ` Lu Baolu
2022-02-14 7:32 ` Christoph Hellwig
2022-02-14 7:32 ` Christoph Hellwig
2022-02-24 13:05 ` Jason Gunthorpe via iommu
2022-02-24 13:05 ` Jason Gunthorpe
2022-02-14 2:57 ` [PATCH v2 08/11] iommu/vt-d: Fix indentation of goto labels Lu Baolu
2022-02-14 2:57 ` Lu Baolu
2022-02-14 7:33 ` Christoph Hellwig
2022-02-14 7:33 ` Christoph Hellwig
2022-02-24 13:08 ` Jason Gunthorpe via iommu
2022-02-24 13:08 ` Jason Gunthorpe
2022-02-25 1:57 ` Lu Baolu
2022-02-25 1:57 ` Lu Baolu
2022-02-14 2:57 ` [PATCH v2 09/11] iommu/vt-d: Remove commented code Lu Baolu
2022-02-14 2:57 ` Lu Baolu
2022-02-14 7:34 ` Christoph Hellwig
2022-02-14 7:34 ` Christoph Hellwig
2022-02-16 3:45 ` Tian, Kevin
2022-02-16 3:45 ` Tian, Kevin
2022-02-16 7:11 ` Lu Baolu [this message]
2022-02-16 7:11 ` Lu Baolu
2022-02-24 13:09 ` Jason Gunthorpe via iommu
2022-02-24 13:09 ` Jason Gunthorpe
2022-02-25 1:53 ` Lu Baolu
2022-02-25 1:53 ` Lu Baolu
2022-02-14 2:57 ` [PATCH v2 10/11] iommu/vt-d: Use xarray for global device_domain_info Lu Baolu
2022-02-14 2:57 ` Lu Baolu
2022-02-14 7:38 ` Christoph Hellwig
2022-02-14 7:38 ` Christoph Hellwig
2022-02-15 5:54 ` Lu Baolu
2022-02-15 5:54 ` Lu Baolu
2022-02-14 14:00 ` Jason Gunthorpe via iommu
2022-02-14 14:00 ` Jason Gunthorpe
2022-02-15 5:46 ` Lu Baolu
2022-02-15 5:46 ` Lu Baolu
2022-02-14 2:57 ` [PATCH v2 11/11] iommu/vt-d: Use rculist for per-domain device list Lu Baolu
2022-02-14 2:57 ` Lu Baolu
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