linux-kernel - Re: [PATCH v4 0/6] iommu/amd: Use 128-bit cmpxchg operation to update DTE

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Message-ID: <668fac7d-79e1-4cb6-bdf4-e15808cedc46@amd.com>
Date: Mon, 23 Sep 2024 22:03:03 +0700
From: "Suthikulpanit, Suravee" <suravee.suthikulpanit@....com>
To: linux-kernel@...r.kernel.org, iommu@...ts.linux.dev
Cc: joro@...tes.org, robin.murphy@....com, vasant.hegde@....com,
 jgg@...dia.com, kevin.tian@...el.com, jon.grimm@....com,
 santosh.shukla@....com, pandoh@...gle.com, kumaranand@...gle.com
Subject: Re: [PATCH v4 0/6] iommu/amd: Use 128-bit cmpxchg operation to update
 DTE



On 9/17/2024 12:17 AM, Suravee Suthikulpanit wrote:
> This series modifies current implementation to use 128-bit cmpxchg to
> update DTE when needed as specified in the AMD I/O Virtualization
> Techonology (IOMMU) Specification.
> 
> Please note that I have verified with the hardware designer, and they have
> confirmed that the IOMMU hardware has always been implemented with 256-bit
> read. The next revision of the IOMMU spec will be updated to correctly
> describe this part.  Therefore, I have updated the implementation to avoid
> unnecessary flushing.
> 
> Changes in v4:
>    * Patch 1: Update commit message
>    * Patch 2:
>      - Move get_dte256, clone_alias, dump_dte to patch 4
>      - Introduce write_upper, write_lower
>      - Introduce iommu_flush_sync_dte
>      - Reimplement update_dte256
>    * Patch 3: Remove spinlock since it is moved inside update_dte256()
>    * Patch 4: Update clone_alias() and dump_dte()
>    * Patch 5: Update clear_dte_entry()
> 
> v3: https://lore.kernel.org/lkml/20240906121308.5013-1-suravee.suthikulpanit@amd.com/
> v2: https://lore.kernel.org/lkml/20240829180726.5022-1-suravee.suthikulpanit@amd.com/
> v1: https://lore.kernel.org/lkml/20240819161839.4657-1-suravee.suthikulpanit@amd.com/
> 
> Thanks,
> Suravee
> 
> Suravee Suthikulpanit (6):
>    iommu/amd: Disable AMD IOMMU if CMPXCHG16B feature is not supported
>    iommu/amd: Introduce helper function to update 256-bit DTE
>    iommu/amd: Modify set_dte_entry() to use 256-bit DTE helpers
>    iommu/amd: Introduce helper function get_dte256()
>    iommu/amd: Modify clear_dte_entry() to avoid in-place update
>    iommu/amd: Lock DTE before updating the entry with WRITE_ONCE()
> 
>   drivers/iommu/amd/amd_iommu.h       |   2 +
>   drivers/iommu/amd/amd_iommu_types.h |  10 +-
>   drivers/iommu/amd/init.c            |  23 +-
>   drivers/iommu/amd/iommu.c           | 332 ++++++++++++++++++++--------
>   4 files changed, 265 insertions(+), 102 deletions(-)
> 

I am rebasing and will resend this patch series.

Suravee