From: Joerg Roedel <jroedel-l3A5Bk7waGM@public.gmane.org>
To: Baoquan He <bhe-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH v8 10/13] iommu/amd: Allocate memory below 4G for dev table if translation pre-enabled
Date: Thu, 27 Jul 2017 17:55:50 +0200 [thread overview]
Message-ID: <20170727155550.GO3610@suse.de> (raw)
In-Reply-To: <1500627551-12930-11-git-send-email-bhe-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
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.
next prev parent reply other threads:[~2017-07-27 15:55 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 8:59 ` [PATCH v8 03/13] Revert "iommu/amd: Suppress IO_PAGE_FAULTs in kdump kernel" 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
[not found] ` <20170727153825.GM3610-l3A5Bk7waGM@public.gmane.org>
2017-07-28 6:52 ` Baoquan He
[not found] ` <1500627551-12930-1-git-send-email-bhe-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
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
[not found] ` <20170727150612.GK3610-l3A5Bk7waGM@public.gmane.org>
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 04/13] iommu/amd: Define bit fields for DTE particularly 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 09/13] iommu/amd: Use is_attach_deferred call-back Baoquan He
[not found] ` <1500627551-12930-10-git-send-email-bhe-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2017-07-27 15:53 ` Joerg Roedel
[not found] ` <20170727155327.GN3610-l3A5Bk7waGM@public.gmane.org>
2017-07-28 4:02 ` 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 10/13] iommu/amd: Allocate memory below 4G for dev table if translation pre-enabled Baoquan He
[not found] ` <1500627551-12930-11-git-send-email-bhe-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2017-07-27 15:55 ` Joerg Roedel [this message]
2017-07-28 9:06 ` Baoquan He
2017-07-28 11:14 ` Joerg Roedel
2017-07-28 11:15 ` Baoquan He
2017-07-28 11:18 ` Joerg Roedel
[not found] ` <20170728111809.GC3431-l3A5Bk7waGM@public.gmane.org>
2017-07-28 11:26 ` Baoquan He
2017-07-31 10:15 ` Baoquan He
2017-07-31 10:21 ` Joerg Roedel
[not found] ` <20170731102153.GK3431-l3A5Bk7waGM@public.gmane.org>
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
[not found] ` <1500627551-12930-12-git-send-email-bhe-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2017-07-23 22:33 ` kbuild test robot
[not found] ` <201707240618.mJ6b2eHv%fengguang.wu-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-07-23 23:53 ` Baoquan He
2017-07-27 15:57 ` Joerg Roedel
[not found] ` <20170727155755.GP3610-l3A5Bk7waGM@public.gmane.org>
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
[not found] ` <1500627551-12930-14-git-send-email-bhe-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2017-07-27 15:58 ` Joerg Roedel
[not found] ` <20170727155852.GQ3610-l3A5Bk7waGM@public.gmane.org>
2017-07-28 9:08 ` Baoquan He
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