linux-kernel - Re: [PATCH v7 3/4] iommufd: Add IOMMU_GET_HW

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Message-ID: <ZNuogZV2eEeVwNX4@nvidia.com>
Date:   Tue, 15 Aug 2023 13:32:01 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Yi Liu <yi.l.liu@...el.com>
Cc:     joro@...tes.org, alex.williamson@...hat.com, kevin.tian@...el.com,
        robin.murphy@....com, baolu.lu@...ux.intel.com, cohuck@...hat.com,
        eric.auger@...hat.com, nicolinc@...dia.com, kvm@...r.kernel.org,
        mjrosato@...ux.ibm.com, chao.p.peng@...ux.intel.com,
        yi.y.sun@...ux.intel.com, peterx@...hat.com, jasowang@...hat.com,
        shameerali.kolothum.thodi@...wei.com, lulu@...hat.com,
        suravee.suthikulpanit@....com, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        zhenzhong.duan@...el.com
Subject: Re: [PATCH v7 3/4] iommufd: Add IOMMU_GET_HW_INFO

On Fri, Aug 11, 2023 at 12:15:00AM -0700, Yi Liu wrote:

> +static int iommufd_get_hw_info(struct iommufd_ucmd *ucmd)
> +{
> +	struct iommu_hw_info *cmd = ucmd->cmd;
> +	unsigned int length = cmd->data_len;
> +	struct iommufd_device *idev;
> +	void __user *user_ptr;
> +	u32 hw_info_type;
> +	int rc = 0;
> +
> +	if (cmd->flags || cmd->__reserved || !cmd->data_len)
> +		return -EOPNOTSUPP;

Is there a reason to block 0 data_len? I think this should work. The
code looks OK?

Jason