linux-kernel - Re: [PATCH v3 15/16] iommu: introduce page response function

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Message-ID: <93661c1c-2d3b-295f-0b9d-52e50ea9e1d0@arm.com>
Date:   Fri, 24 Nov 2017 12:03:50 +0000
From:   Jean-Philippe Brucker <jean-philippe.brucker@....com>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rafael Wysocki <rafael.j.wysocki@...el.com>,
        Alex Williamson <alex.williamson@...hat.com>
Cc:     Lan Tianyu <tianyu.lan@...el.com>,
        Jean Delvare <khali@...ux-fr.org>
Subject: Re: [PATCH v3 15/16] iommu: introduce page response function

On 17/11/17 18:55, Jacob Pan wrote:
> When nested translation is turned on and guest owns the
> first level page tables, device page request can be forwared
> to the guest for handling faults. As the page response returns
> by the guest, IOMMU driver on the host need to process the
> response which informs the device and completes the page request
> transaction.
> 
> This patch introduces generic API function for page response
> passing from the guest or other in-kernel users. The definitions of
> the generic data is based on PCI ATS specification not limited to
> any vendor.>
> Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> ---
>  drivers/iommu/iommu.c | 14 ++++++++++++++
>  include/linux/iommu.h | 42 ++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 56 insertions(+)
> 
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 97b7990..7aefb40 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -1416,6 +1416,20 @@ int iommu_sva_invalidate(struct iommu_domain *domain,
>  }
>  EXPORT_SYMBOL_GPL(iommu_sva_invalidate);
>  
> +int iommu_page_response(struct iommu_domain *domain, struct device *dev,
> +			struct page_response_msg *msg)

I think it's simpler, both for IOMMU and device drivers, to pass the exact
structure received in the fault handler back to the IOMMU driver, along
with a separate response status. So maybe

int iommu_page_response(struct iommu_domain *domain, struct device *dev,
			struct iommu_fault_event *event, u32 response)

And then you'd just need to define the IOMMU_PAGE_RESPONSE_* values.

Thanks,
Jean