linux-kernel - Re: [RFC PATCH] vfio: type1: fix kthread use case

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Date:   Mon, 6 Jul 2020 16:04:13 +0200
From:   Markus Elfring <Markus.Elfring@....de>
To:     Hillf Danton <hdanton@...a.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        iommu@...ts.linux-foundation.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org,
        Christoph Hellwig <hch@....de>,
        Jörg Rödel <joro@...tes.org>,
        Kevin Tian <kevin.tian@...el.com>,
        Yan Zhao <yan.y.zhao@...el.com>
Subject: Re: [RFC PATCH] vfio: type1: fix kthread use case

…
> +++ b/drivers/vfio/vfio_iommu_type1.c
…
> @@ -2812,11 +2815,10 @@ static int vfio_iommu_type1_dma_rw_chunk
…
>  	if (!mm)
>  		return -EPERM;
>
> -	if (kthread)
> +	if (kthread && use_mm)

Can another design approach make sense here?

+	bool thread_use_mm = ((current->flags & PF_KTHREAD) && !current->mm);
+	if (thread_use_mm)


>  		kthread_use_mm(mm);
…

Regards,
Markus