From: sathyanarayanan kuppuswamy <sathyanarayanan.kuppuswamy@linux.intel.com>
To: "Raj, Ashok" <ashok.raj@intel.com>, Sinan Kaya <Okaya@kernel.org>
Cc: bhelgaas@google.com, joro@8bytes.org, dwmw2@infradead.org,
linux-pci@vger.kernel.org, iommu@lists.linux-foundation.org,
linux-kernel@vger.kernel.org,
Jacob Pan <jacob.jun.pan@linux.intel.com>,
Keith Busch <keith.busch@intel.com>
Subject: Re: [PATCH v1 1/2] PCI: ATS: Add function to check ATS page aligned request status.
Date: Mon, 11 Feb 2019 11:24:22 -0800 [thread overview]
Message-ID: <40d67487-3881-2e3b-c2cd-424333b0abc5@linux.intel.com> (raw)
In-Reply-To: <20190211191549.GA12090@otc-nc-03>
On 2/11/19 11:15 AM, Raj, Ashok wrote:
> On Fri, Feb 08, 2019 at 11:49:55PM -0500, Sinan Kaya wrote:
>> On 2/8/2019 8:02 PM, sathyanarayanan kuppuswamy wrote:
>>>> This means that you should probably have some kind of version check
>>>> here.
>>> There is no version field in ATS v1.0 spec. Also, If I follow the history
>>> log in PCI spec, I think ATS if first added at v1.2. Please correct me if
>>> I am wrong.
>> v1.2 was incorporated into PCIe spec at that time. However, the ATS spec
>> is old and there could be some HW that could claim to be ATS compatible.
>> I know AMD GPUs declare ATS capability.
> It seems rather odd we have to check for ATS version.
>
> I always assumed unspecified bits (Reserved) must be 0. We only check
> this if ATS is enabled, and this particular bit wasn't given away for another
> feature.
>
> Is it really required to check for ATS version before consuming this?
If the version check is required then, it needs to be added before
reading "Invalidate Queue Depth" value as well.
>
>
>> See this ECN
>>
>> https://composter.com.ua/documents/ats_r1.1_26Jan09.pdf
>>
>> You need to validate the version field from ATS capability header to be
>> 1 before reading this register.
>>
>> See Table 5-1: ATS Extended Capability Header
--
Sathyanarayanan Kuppuswamy
Linux kernel developer
next prev parent reply other threads:[~2019-02-11 19:25 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-07 18:41 [PATCH v1 0/2] Add page alignment check in Intel IOMMU sathyanarayanan.kuppuswamy
2019-02-07 18:41 ` [PATCH v1 1/2] PCI: ATS: Add function to check ATS page aligned request status sathyanarayanan.kuppuswamy
2019-02-07 20:07 ` Bjorn Helgaas
2019-02-07 20:39 ` sathyanarayanan kuppuswamy
2019-02-07 20:38 ` Sinan Kaya
2019-02-07 22:16 ` sathyanarayanan kuppuswamy
2019-02-08 1:58 ` Sinan Kaya
2019-02-09 1:02 ` sathyanarayanan kuppuswamy
2019-02-09 4:49 ` Sinan Kaya
2019-02-11 19:15 ` Raj, Ashok
2019-02-11 19:24 ` sathyanarayanan kuppuswamy [this message]
2019-02-11 20:35 ` Sinan Kaya
2019-02-07 18:41 ` [PATCH v1 2/2] iommu/vt-d: Enable ATS only if the device uses page aligned address sathyanarayanan.kuppuswamy
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