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

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Message-ID: <ZTcAhwYjjzqM0A5M@Asurada-Nvidia>
Date:   Mon, 23 Oct 2023 16:23:51 -0700
From:   Nicolin Chen <nicolinc@...dia.com>
To:     Jason Gunthorpe <jgg@...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 08:05:09PM -0300, Jason Gunthorpe wrote:
> On Mon, Oct 23, 2023 at 11:57:00AM -0700, Nicolin Chen wrote:
> > According to the conversion in the following link:

Ah, a typo here: conversation.

> > 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?

I will respin a v4 after Kevin's reply. And I can attach his
"Reviewed-by" if everything looks good to him too.

Thanks
Nic