From: Baoquan He <bhe@redhat.com>
To: Joerg Roedel <jroedel@suse.de>
Cc: iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v8 10/13] iommu/amd: Allocate memory below 4G for dev table if translation pre-enabled
Date: Fri, 28 Jul 2017 17:06:19 +0800 [thread overview]
Message-ID: <20170728090619.GM24304@x1> (raw)
In-Reply-To: <20170727155550.GO3610@suse.de>
Hi Joerg,
On 07/27/17 at 05:55pm, Joerg Roedel wrote:
> On Fri, Jul 21, 2017 at 04:59:08PM +0800, Baoquan He wrote:
> > AMD pointed out it's unsafe to update the device-table while iommu
> > is enabled. It turns out that device-table pointer update is split
> > up into two 32bit writes in the IOMMU hardware. So updating it while
> > the IOMMU is enabled could have some nasty side effects.
> >
> > The only way to work around this is to allocate the device-table below
> > 4GB if translation is pre-enabled in kdump kernel. If allocation failed,
> > still use the old one.
>
> Not only for the kdump kernel. The old device table must also be below
> 4GB so that its pointer can be updated with a 32bit write.
>
> If the old table is above 4GB you still need the second write to zero
> the upper parts of the pointer in hardware.
Do you mean the allocation of amd_iommu_dev_table in
early_amd_iommu_init() also need be addressed for 1st kernel? Seems we
don't make sure that for 1st kernel, like adding GFP_DMA32 flag when
allocate amd_iommu_dev_table in amd_iommu_dev_table
early_amd_iommu_init().
next prev parent reply other threads:[~2017-07-28 9:06 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-21 8:58 [PATCH v8 00/13] Fix the on-flight DMA issue on system with amd iommu Baoquan He
2017-07-21 8:58 ` [PATCH v8 01/13] iommu/amd: Detect pre enabled translation Baoquan He
2017-07-27 15:04 ` Joerg Roedel
2017-07-28 2:31 ` Baoquan He
2017-07-21 8:59 ` [PATCH v8 02/13] iommu/amd: add several helper functions Baoquan He
2017-07-27 15:06 ` Joerg Roedel
2017-07-28 2:36 ` Baoquan He
2017-07-31 10:01 ` Baoquan He
2017-07-31 10:07 ` Joerg Roedel
2017-07-21 8:59 ` [PATCH v8 03/13] Revert "iommu/amd: Suppress IO_PAGE_FAULTs in kdump kernel" Baoquan He
2017-07-21 8:59 ` [PATCH v8 04/13] iommu/amd: Define bit fields for DTE particularly Baoquan He
2017-07-21 8:59 ` [PATCH v8 05/13] iommu/amd: Add function copy_dev_tables() Baoquan He
2017-07-27 15:29 ` Joerg Roedel
2017-07-28 3:59 ` Baoquan He
2017-07-21 8:59 ` [PATCH v8 06/13] iommu/amd: copy old trans table from old kernel Baoquan He
2017-07-27 15:38 ` Joerg Roedel
2017-07-28 6:52 ` Baoquan He
2017-07-21 8:59 ` [PATCH v8 07/13] iommu/amd: Do sanity check for irq remap of old dev table entry Baoquan He
2017-07-21 8:59 ` [PATCH v8 08/13] iommu: Add is_attach_deferred call-back to iommu-ops Baoquan He
2017-07-21 8:59 ` [PATCH v8 09/13] iommu/amd: Use is_attach_deferred call-back Baoquan He
2017-07-27 15:53 ` Joerg Roedel
2017-07-28 4:02 ` Baoquan He
2017-07-21 8:59 ` [PATCH v8 10/13] iommu/amd: Allocate memory below 4G for dev table if translation pre-enabled Baoquan He
2017-07-27 15:55 ` Joerg Roedel
2017-07-28 9:06 ` Baoquan He [this message]
2017-07-28 11:14 ` Joerg Roedel
2017-07-28 11:15 ` Baoquan He
2017-07-28 11:18 ` Joerg Roedel
2017-07-28 11:26 ` Baoquan He
2017-07-31 10:15 ` Baoquan He
2017-07-31 10:21 ` Joerg Roedel
2017-07-31 10:29 ` Baoquan He
2017-07-21 8:59 ` [PATCH v8 11/13] iommu/amd: Don't copy GCR3 table root pointer Baoquan He
2017-07-23 22:33 ` kbuild test robot
2017-07-23 23:53 ` Baoquan He
2017-07-27 15:57 ` Joerg Roedel
2017-07-28 9:07 ` Baoquan He
2017-07-21 8:59 ` [PATCH v8 12/13] iommu/amd: Clear out the GV flag when handle deferred domain attach Baoquan He
2017-07-21 8:59 ` [PATCH v8 13/13] iommu/amd: Disable iommu only if amd_iommu=off is specified Baoquan He
2017-07-27 15:58 ` Joerg Roedel
2017-07-28 9:08 ` Baoquan He
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