linux-kernel - Re: [PATCH v6 0/9] Fix kdump faults on system with amd iommu

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Message-ID: <20161104051459.GB4314@x1>
Date:   Fri, 4 Nov 2016 13:14:59 +0800
From:   Baoquan He <bhe@...hat.com>
To:     joro@...tes.org
Cc:     iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        kexec@...ts.infradead.org, Vincent.Wan@....com, dyoung@...hat.com,
        xlpang@...hat.com
Subject: Re: [PATCH v6 0/9] Fix kdump faults on system with amd iommu

Hi Joerg,

Ping!

About the v6 post, do you have any suggestions?

Because of GCR3 special handling in patch 9/9, I spent several days to
study the knowledge and change code. Then when I tried to post, the
virtual interrupt remapping feature caused kernel hang with this pachset
applied. So it took me days to study spec and find it out. Finally it's
very late to post.

Coule it be possibe that we review and merge patch 9/1~8, and leave the
patch 9/9 which includes GCR3 special handling as 2nd step issue? Then
I can back port patch 9/1~8 to our distro. Since this bug has been
discussed so long time, and currently almost all system are deployed
with amd iommu v1 hardware. It would be great if they can be accepted
into 4.9 or 4.10-rc phase.

About patch 9/9, its code is a little complicated and not being
reviewed, I am not sure if I understand your suggestion and GCR3 code
well. What's your opinion?

Thanks
Baoquan


On 10/20/16 at 07:37pm, Baoquan He wrote:
> This is v6 post. 
> 
> The principle of the fix is similar to intel iommu. Just defer the assignment
> of device to domain to device driver init. But there's difference than
> intel iommu. AMD iommu create protection domain and assign device to
> domain in iommu driver init stage. So in this patchset I just allow the
> assignment of device to domain in software level, but defer updating the
> domain info, especially the pte_root to dev table entry to device driver
> init stage.
> 
> v5: 
>     bnx2 NIC can't reset itself during driver init. Post patch to reset
>     it during driver init. IO_PAGE_FAULT can't be seen anymore.
>     
>     Below is link of v5 post.
>     https://lists.linuxfoundation.org/pipermail/iommu/2016-September/018527.html
> 
> v5->v6:
>     According to Joerg's comments made several below main changes:
>     - Add sanity check when copy old dev tables. 
> 
>     - Discard the old patch 6/8.
> 
>     - If a device is set up with guest translations (DTE.GV=1), then don't
>       copy that information but move the device over to an empty guest-cr3
>       table and handle the faults in the PPR log (which just answer them
>       with INVALID).
> 
> Issues need be discussed:
>     - Joerg suggested hooking the behaviour that updates domain info into
>       dte entry into the set_dma_mask call-back. I tried, but on my local
>       machine with amd iommu v2, an ohci pci device doesn't call set_dma_mask.
>       Then IO_PAGE_FAULT printing flooded.
> 
>       00:12.0 USB controller: Advanced Micro Devices, Inc. [AMD] FCH USB OHCI Controller (rev 11)
> 
>     - About GCR3 root pointer copying issue, I don't know how to setup the
>       test environment and haven't tested yet. Hope Joerg or Zongshun can
>       tell what steps should be taken to test it, or help take a test in your
>       test environemnt.
>  
> Baoquan He (9):
>   iommu/amd: Detect pre enabled translation
>   iommu/amd: add several helper function
>   iommu/amd: Define bit fields for DTE particularly
>   iommu/amd: Add function copy_dev_tables
>   iommu/amd: copy old trans table from old kernel
>   iommu/amd: Don't update domain info to dte entry at iommu init stage
>   iommu/amd: Update domain into to dte entry during device driver init
>   iommu/amd: Add sanity check of irq remap information of old dev table
>     entry
>   iommu/amd: Don't copy GCR3 table root pointer
> 
>  drivers/iommu/amd_iommu.c       |  93 +++++++++++++-------
>  drivers/iommu/amd_iommu_init.c  | 189 +++++++++++++++++++++++++++++++++++++---
>  drivers/iommu/amd_iommu_proto.h |   2 +
>  drivers/iommu/amd_iommu_types.h |  53 ++++++++++-
>  drivers/iommu/amd_iommu_v2.c    |  18 +++-
>  5 files changed, 307 insertions(+), 48 deletions(-)
> 
> -- 
> 2.5.5
>