linux-kernel - Re: [PATCH] iommu/vt-d: Flush old iotlb for kdump when the device gets context mapped

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Message-ID: <20161130142642.GJ2078@8bytes.org>
Date:   Wed, 30 Nov 2016 15:26:43 +0100
From:   Joerg Roedel <joro@...tes.org>
To:     Baoquan He <bhe@...hat.com>
Cc:     xlpang@...hat.com, Don Brace <don.brace@...rosemi.com>,
        Myron Stowe <myron.stowe@...hat.com>,
        kexec@...ts.infradead.org, LKML <linux-kernel@...r.kernel.org>,
        iommu@...ts.linux-foundation.org,
        Myron Stowe <myron.stowe@...il.com>,
        Dave Young <dyoung@...hat.com>,
        David Woodhouse <dwmw2@...radead.org>
Subject: Re: [PATCH] iommu/vt-d: Flush old iotlb for kdump when the device
 gets context mapped

On Wed, Nov 30, 2016 at 06:23:34PM +0800, Baoquan He wrote:
> OK, talked with Xunlei. The old cache could be entry with present bit
> set.

-EPARSE

Anyway, what I was trying to say is, that the IOMMU TLB is tagged with
domain-ids, and that there is also a context-cache which maps device-ids
to domain-ids.

If we update the context entry then we need to flush only the context
entry, as it will point to a new domain-id then and future IOTLB lookups
in the IOMMU will be using the new domain-id and do not match the old
entries.

	Joerg