linux-kernel - Re: [PATCH v3] iommufd: Only enforce cache coherency in iommufd_hw_pagetable

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Message-ID: <20231023230509.GI3952@nvidia.com>
Date:   Mon, 23 Oct 2023 20:05:09 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Nicolin Chen <nicolinc@...dia.com>
Cc:     kevin.tian@...el.com, joro@...tes.org, will@...nel.org,
        robin.murphy@....com, baolu.lu@...ux.intel.com,
        iommu@...ts.linux.dev, linux-kernel@...r.kernel.org,
        yi.l.liu@...el.com
Subject: Re: [PATCH v3] iommufd: Only enforce cache coherency in
 iommufd_hw_pagetable_alloc

On Mon, Oct 23, 2023 at 11:57:00AM -0700, Nicolin Chen wrote:
> According to the conversion in the following link:
> https://lore.kernel.org/linux-iommu/20231020135501.GG3952@nvidia.com/
> 
> The enforce_cache_coherency should be set/enforced in the hwpt allocation
> routine. The iommu driver in its attach_dev() op should decide whether to
> reject or not a device that doesn't match with the configuration of cache
> coherency. Drop the enforce_cache_coherency piece in the attach/replace()
> and move the remaining "num_devices" piece closer to the refcount that is
> using it.
> 
> Accordingly drop its function prototype in the header and mark it static.
> Also add some extra comments to clarify the expected behaviors.
> 
> Suggested-by: Kevin Tian <kevin.tian@...el.com>
> Reviewed-by: Lu Baolu <baolu.lu@...ux.intel.com>
> Signed-off-by: Nicolin Chen <nicolinc@...dia.com>
> ---
> Changelog
> v3:
>  * Reworked the first line of the added commets.
> v2: https://lore.kernel.org/all/20231023035733.27378-1-nicolinc@nvidia.com/
>  * Dropped "fixes" tags and merged two patches into one (Jason)
>  * Added comments to the remaining enforce_cache_coherency call (Jason)
>    [Please feel free to rephrase, or let me know what to change.]
>  * Replace "num_devices++" with list_for_each_entry (Baolu)
> v1: https://lore.kernel.org/all/cover.1697848510.git.nicolinc@nvidia.com/
> 
>  drivers/iommu/iommufd/device.c          | 20 ++------------------
>  drivers/iommu/iommufd/hw_pagetable.c    |  9 ++++++++-
>  drivers/iommu/iommufd/iommufd_private.h |  1 -
>  3 files changed, 10 insertions(+), 20 deletions(-)

This looks OK to me, Kevin is it what you think it should be now?

Thanks,
Jason