linux-kernel - Re: [PATCH v7 09/10] hisi_acc_vfio_pci: Add support for VFIO live migration

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Date:   Wed, 2 Mar 2022 20:21:42 -0400
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-crypto@...r.kernel.org, linux-pci@...r.kernel.org,
        alex.williamson@...hat.com, cohuck@...hat.com,
        mgurtovoy@...dia.com, yishaih@...dia.com, linuxarm@...wei.com,
        liulongfang@...wei.com, prime.zeng@...ilicon.com,
        jonathan.cameron@...wei.com, wangzhou1@...ilicon.com
Subject: Re: [PATCH v7 09/10] hisi_acc_vfio_pci: Add support for VFIO live
 migration

On Wed, Mar 02, 2022 at 05:29:02PM +0000, Shameer Kolothum wrote:
> +static long hisi_acc_vf_save_unl_ioctl(struct file *filp,
> +				       unsigned int cmd, unsigned long arg)
> +{
> +	struct hisi_acc_vf_migration_file *migf = filp->private_data;
> +	struct hisi_acc_vf_core_device *hisi_acc_vdev = container_of(migf,
> +			struct hisi_acc_vf_core_device, saving_migf);
> +	loff_t *pos = &filp->f_pos;
> +	struct vfio_precopy_info info;
> +	unsigned long minsz;
> +	int ret;
> +
> +	if (cmd != VFIO_MIG_GET_PRECOPY_INFO)
> +		return -ENOTTY;
> +
> +	minsz = offsetofend(struct vfio_precopy_info, dirty_bytes);
> +
> +	if (copy_from_user(&info, (void __user *)arg, minsz))
> +		return -EFAULT;
> +	if (info.argsz < minsz)
> +		return -EINVAL;
> +
> +	mutex_lock(&hisi_acc_vdev->state_mutex);
> +	if (hisi_acc_vdev->mig_state != VFIO_DEVICE_STATE_PRE_COPY) {
> +		mutex_unlock(&hisi_acc_vdev->state_mutex);
> +		return -EINVAL;
> +	}

IMHO it is easier just to check the total_length and not grab this
other lock

> +struct acc_vf_data {
> +#define QM_MATCH_SIZE 32L

This should be

#define QM_MATCH_SIZE offsetofend(struct acc_vf_data, qm_rsv_state)

> +	/* QM match information */

You should probably put an 8 byte random magic number here just to
make the compatibility more unique.

> +	u32 qp_num;
> +	u32 dev_id;
> +	u32 que_iso_cfg;
> +	u32 qp_base;
> +	/* QM reserved match information */
> +	u32 qm_rsv_state[4];
> +
> +	/* QM RW regs */
> +	u32 aeq_int_mask;
> +	u32 eq_int_mask;
> +	u32 ifc_int_source;
> +	u32 ifc_int_mask;
> +	u32 ifc_int_set;
> +	u32 page_size;
> +
> +	/* QM_EQC_DW has 7 regs */
> +	u32 qm_eqc_dw[7];
> +
> +	/* QM_AEQC_DW has 7 regs */
> +	u32 qm_aeqc_dw[7];
> +
> +	/* QM reserved 5 regs */
> +	u32 qm_rsv_regs[5];
> +
> +	/* qm memory init information */
> +	u64 eqe_dma;

Am I counting wrong or is there a padding before this? 7+7+5 is not a multiple
of 2. Be explicit about padding in a structure like this.

Jason