linux-kernel - Re: [RFC PATCH] iommu/amd: fix a race in fetch

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Message-ID: <20200429084738.GM21900@8bytes.org>
Date:   Wed, 29 Apr 2020 10:47:38 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     Qian Cai <cai@....pw>
Cc:     iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] iommu/amd: fix a race in fetch_pte()

Hi Qian,

On Mon, Apr 20, 2020 at 09:26:12AM -0400, Qian Cai wrote:
> 
> No dice. There could be some other races. For example,

Okay, I think I know what is happening. The increase_address_space()
function increases the address space, but does not update the
DTE and does not flush the old DTE from the caches. But this needs to
happen before domain->pt_root is updated, because otherwise another CPU
can come along and map something into the increased address-space which
is not yet accessible by the device because the DTE is not updated yet.

Regards,

	Joerg