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From: Jacob Pan <jacob.jun.pan@linux.intel.com>
To: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>,
	"Raj, Ashok" <ashok.raj@intel.com>,
	"jean-philippe@linaro.org" <jean-philippe@linaro.org>
Cc: "Tian, Kevin" <kevin.tian@intel.com>,
	"Lu, Baolu" <baolu.lu@intel.com>,
	"iommu@lists.linux-foundation.org"
	<iommu@lists.linux-foundation.org>, "Wu, Hao" <hao.wu@intel.com>
Subject: Re: IOASID set token
Date: Thu, 2 Jul 2020 06:48:25 -0700	[thread overview]
Message-ID: <20200702064825.20f9d2b1@jacob-builder> (raw)
In-Reply-To: <20200701232916.38fd7908@jacob-builder>

Hi Jean,

Just realized I should send this to your Linaro account instead of ARM.
So Hi again :)

On Wed, 1 Jul 2020 23:29:16 -0700
Jacob Pan <jacob.jun.pan@linux.intel.com> wrote:

> Hi Jean,
> 
> Have a question for you on whether we can have a fixed token type for
> ioasid_set.
> 
> Currently, ioasid_set has an arbitrary token. For VT-d vSVA usage, we
> choose mm as ioasid_set token to identify PASIDs within a guest. We
> have multiple in-kernel users of PASIDs such as VFIO, KVM, and VDCM.
> When an IOASID set is created, there is not a good way to communicate
> about the token choices. So we have to let VDCM and KVM *assume* mm
> is used as token, then retrieve ioasid_set based on the token.
> 
> This assumption of "mm as token" is not a reliable SW architecture. So
> we are thinking if we can have an explicit ioasid_set token type where
> mm is used. After all, PASID and mm are closely related.
> 
> The code change might be the following:
> 1. add a flag to indicate token type when ioasid_set is allocated,
> e.g. IOASID_SET_TYPE_MM
> IOASID_SET_TYPE_ANY
> 2. other users of the ioasid_set can query if an mm token exists based
> on the flag IOASID_SET_TYPE_MM, then retrieve the ioasid_set.
> 
> Existing ioasid_set user can still use arbitrary token under the flag
> IOASID_SET_TYPE_ANY
> 
> Would this be an issue for ARM usage?
> 
> Thanks,
> 
> Jacob

[Jacob Pan]
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  reply	other threads:[~2020-07-02 13:41 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-02  6:29 Jacob Pan
2020-07-02 13:48 ` Jacob Pan [this message]
2020-07-06 10:30   ` Jean-Philippe Brucker
2020-07-06 20:51     ` Jacob Pan
2020-07-07 10:07       ` Jean-Philippe Brucker
2020-07-07 15:38         ` Jacob Pan

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