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From: Jacob Pan <>
To: Jean-Philippe Brucker <>,
	"Raj, Ashok" <>
Cc: "Tian, Kevin" <>,
	"Lu, Baolu" <>,
	<>, "Wu, Hao" <>
Subject: IOASID set token
Date: Wed, 1 Jul 2020 23:29:16 -0700	[thread overview]
Message-ID: <20200701232916.38fd7908@jacob-builder> (raw)

Hi Jean,

Have a question for you on whether we can have a fixed token type for

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.
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

Would this be an issue for ARM usage?


iommu mailing list

             reply	other threads:[~2020-07-02  6:22 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-02  6:29 Jacob Pan [this message]
2020-07-02 13:48 ` Jacob Pan
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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