netdev - Re: [PATCH V4 vfio 05/10] vfio: Introduce the DMA logging feature support

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Message-ID: <20220825144944.237eb78f.alex.williamson@redhat.com>
Date:   Thu, 25 Aug 2022 14:49:44 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Yishai Hadas <yishaih@...dia.com>
Cc:     <jgg@...dia.com>, <saeedm@...dia.com>, <kvm@...r.kernel.org>,
        <netdev@...r.kernel.org>, <kuba@...nel.org>,
        <kevin.tian@...el.com>, <joao.m.martins@...cle.com>,
        <leonro@...dia.com>, <maorg@...dia.com>, <cohuck@...hat.com>
Subject: Re: [PATCH V4 vfio 05/10] vfio: Introduce the DMA logging feature
 support

On Mon, 15 Aug 2022 18:11:04 +0300
Yishai Hadas <yishaih@...dia.com> wrote:
> +static int
> +vfio_ioctl_device_feature_logging_report(struct vfio_device *device,
> +					 u32 flags, void __user *arg,
> +					 size_t argsz)
> +{
> +	size_t minsz =
> +		offsetofend(struct vfio_device_feature_dma_logging_report,
> +			    bitmap);
> +	struct vfio_device_feature_dma_logging_report report;
> +	struct iova_bitmap_iter iter;
> +	int ret;
> +
> +	if (!device->log_ops)
> +		return -ENOTTY;
> +
> +	ret = vfio_check_feature(flags, argsz,
> +				 VFIO_DEVICE_FEATURE_GET,
> +				 sizeof(report));
> +	if (ret != 1)
> +		return ret;
> +
> +	if (copy_from_user(&report, arg, minsz))
> +		return -EFAULT;
> +
> +	if (report.page_size < PAGE_SIZE || !is_power_of_2(report.page_size))

Why is PAGE_SIZE a factor here?  I'm under the impression that
iova_bitmap is intended to handle arbitrary page sizes.  Thanks,

Alex

> +		return -EINVAL;
> +
> +	ret = iova_bitmap_iter_init(&iter, report.iova, report.length,
> +				    report.page_size,
> +				    u64_to_user_ptr(report.bitmap));
> +	if (ret)
> +		return ret;
> +
> +	for (; !iova_bitmap_iter_done(&iter) && !ret;
> +	     ret = iova_bitmap_iter_advance(&iter)) {
> +		ret = device->log_ops->log_read_and_clear(device,
> +			iova_bitmap_iova(&iter),
> +			iova_bitmap_length(&iter), &iter.dirty);
> +		if (ret)
> +			break;
> +	}
> +
> +	iova_bitmap_iter_free(&iter);
> +	return ret;
> +}