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From: Joerg Roedel <joro@8bytes.org>
To: Qian Cai <cai@lca.pw>
Cc: iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH] iommu/amd: fix a race in fetch_pte()
Date: Wed, 29 Apr 2020 10:47:38 +0200	[thread overview]
Message-ID: <20200429084738.GM21900@8bytes.org> (raw)
In-Reply-To: <7D03A3E2-647B-4FAD-886D-EE2764EC1EDB@lca.pw>

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
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

WARNING: multiple messages have this Message-ID (diff)
From: Joerg Roedel <joro@8bytes.org>
To: Qian Cai <cai@lca.pw>
Cc: iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH] iommu/amd: fix a race in fetch_pte()
Date: Wed, 29 Apr 2020 10:47:38 +0200	[thread overview]
Message-ID: <20200429084738.GM21900@8bytes.org> (raw)
In-Reply-To: <7D03A3E2-647B-4FAD-886D-EE2764EC1EDB@lca.pw>

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

  reply	other threads:[~2020-04-29  8:47 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-07  2:12 [RFC PATCH] iommu/amd: fix a race in fetch_pte() Qian Cai
2020-04-07  2:12 ` Qian Cai
2020-04-07 15:36 ` Qian Cai
2020-04-07 15:36   ` Qian Cai
2020-04-08 14:19   ` Joerg Roedel
2020-04-08 14:19     ` Joerg Roedel
2020-04-14  1:36     ` Qian Cai
2020-04-14  1:36       ` Qian Cai
2020-04-17  1:42       ` Qian Cai
2020-04-17  1:42         ` Qian Cai
2020-04-18 12:10         ` Joerg Roedel
2020-04-18 12:10           ` Joerg Roedel
2020-04-18 13:01           ` Qian Cai
2020-04-18 13:01             ` Qian Cai
2020-04-18 18:34             ` Joerg Roedel
2020-04-18 18:34               ` Joerg Roedel
2020-04-20  2:07               ` Qian Cai
2020-04-20  2:07                 ` Qian Cai
2020-04-20 13:26               ` Qian Cai
2020-04-20 13:26                 ` Qian Cai
2020-04-29  8:47                 ` Joerg Roedel [this message]
2020-04-29  8:47                   ` Joerg Roedel
2020-04-29 11:20                 ` Joerg Roedel
2020-04-29 11:20                   ` Joerg Roedel
2020-04-30  1:04                   ` Qian Cai
2020-04-30  1:04                     ` Qian Cai
2020-05-03 13:04                   ` Qian Cai
2020-05-03 13:04                     ` Qian Cai
2020-05-03 18:39                     ` Joerg Roedel
2020-05-03 18:39                       ` Joerg Roedel
2020-05-03 19:12                       ` Qian Cai
2020-05-03 19:12                         ` Qian Cai

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