linux-kernel - Re: [PATCH 1/2] iommu: Prevent RESV_DIRECT devices from blocking domains

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Message-ID: <ZJsEo2eqDdV0Mska@nvidia.com>
Date:   Tue, 27 Jun 2023 12:47:47 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Baolu Lu <baolu.lu@...ux.intel.com>
Cc:     "Tian, Kevin" <kevin.tian@...el.com>,
        "Liu, Jingqi" <jingqi.liu@...el.com>,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Nicolin Chen <nicolinc@...dia.com>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] iommu: Prevent RESV_DIRECT devices from blocking
 domains

On Tue, Jun 27, 2023 at 04:01:01PM +0800, Baolu Lu wrote:

> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index e59de7852067..3be88b5f36bb 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -962,6 +962,9 @@ static int iommu_create_device_direct_mappings(struct
> iommu_domain *domain,
>         pg_size = domain->pgsize_bitmap ? 1UL <<
> __ffs(domain->pgsize_bitmap) : 0;
>         INIT_LIST_HEAD(&mappings);
> 
> +       if (WARN_ON_ONCE((domain->type & __IOMMU_DOMAIN_PAGING) &&
> !pg_size))
> +               return -EINVAL;

Calling this function with an identity domain is expected, it must
return 0.

Jason