linux-kernel - Re: [PATCH v3 24/25] iommu/dma: Factor out flush queue init

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Message-ID: <20210809125238.GB1097@willie-the-truck>
Date:   Mon, 9 Aug 2021 13:52:39 +0100
From:   Will Deacon <will@...nel.org>
To:     Robin Murphy <robin.murphy@....com>
Cc:     joro@...tes.org, linux-kernel@...r.kernel.org,
        dianders@...omium.org, iommu@...ts.linux-foundation.org,
        rajatja@...gle.com, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 24/25] iommu/dma: Factor out flush queue init

On Wed, Aug 04, 2021 at 06:15:52PM +0100, Robin Murphy wrote:
> Factor out flush queue setup from the initial domain init so that we
> can potentially trigger it from sysfs later on in a domain's lifetime.
> 
> Reviewed-by: Lu Baolu <baolu.lu@...ux.intel.com>
> Reviewed-by: John Garry <john.garry@...wei.com>
> Signed-off-by: Robin Murphy <robin.murphy@....com>
> ---
>  drivers/iommu/dma-iommu.c | 30 ++++++++++++++++++++----------
>  include/linux/dma-iommu.h |  9 ++++++---
>  2 files changed, 26 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index 2e19505dddf9..f51b8dc99ac6 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -310,6 +310,25 @@ static bool dev_is_untrusted(struct device *dev)
>  	return dev_is_pci(dev) && to_pci_dev(dev)->untrusted;
>  }
>  
> +int iommu_dma_init_fq(struct iommu_domain *domain)
> +{
> +	struct iommu_dma_cookie *cookie = domain->iova_cookie;
> +
> +	if (domain->type != IOMMU_DOMAIN_DMA_FQ)
> +		return -EINVAL;
> +	if (cookie->fq_domain)
> +		return 0;
> +
> +	if (init_iova_flush_queue(&cookie->iovad, iommu_dma_flush_iotlb_all,
> +				  iommu_dma_entry_dtor)) {
> +		pr_warn("iova flush queue initialization failed\n");
> +		domain->type = IOMMU_DOMAIN_DMA;
> +		return -ENODEV;

I do find this a bit odd: we assert that the caller has set domain->type
to IOMMU_DOMAIN_DMA_FQ but then on failure we reset it to IOMMU_DOMAIN_DMA
here. I think it would be less error-prone if the setting of domain->type
was handled in the same function.

Will