linux-kernel - Re: [RFC PATCH v1 1/4] vfio/type1: Add a bitmap to track IOPF mapped pages

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Date:   Fri, 29 Jan 2021 15:58:12 -0700
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Shenming Lu <lushenming@...wei.com>
Cc:     Cornelia Huck <cohuck@...hat.com>, <kvm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Eric Auger <eric.auger@...hat.com>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Kevin Tian <kevin.tian@...el.com>,
        <wanghaibin.wang@...wei.com>, <yuzenghui@...wei.com>
Subject: Re: [RFC PATCH v1 1/4] vfio/type1: Add a bitmap to track IOPF
 mapped pages

On Mon, 25 Jan 2021 17:03:59 +0800
Shenming Lu <lushenming@...wei.com> wrote:

> When IOPF enabled, the pages are pinned and mapped on demand, we add
> a bitmap to track them.
> 
> Signed-off-by: Shenming Lu <lushenming@...wei.com>
> ---
>  drivers/vfio/vfio_iommu_type1.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 0b4dedaa9128..f1d4de5ab094 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -95,6 +95,7 @@ struct vfio_dma {
>  	struct task_struct	*task;
>  	struct rb_root		pfn_list;	/* Ex-user pinned pfn list */
>  	unsigned long		*bitmap;
> +	unsigned long		*iommu_mapped_bitmap;	/* IOPF mapped bitmap */
>  };
>  
>  struct vfio_group {
> @@ -143,6 +144,8 @@ struct vfio_regions {
>  #define DIRTY_BITMAP_PAGES_MAX	 ((u64)INT_MAX)
>  #define DIRTY_BITMAP_SIZE_MAX	 DIRTY_BITMAP_BYTES(DIRTY_BITMAP_PAGES_MAX)
>  
> +#define IOMMU_MAPPED_BITMAP_BYTES(n) DIRTY_BITMAP_BYTES(n)
> +
>  static int put_pfn(unsigned long pfn, int prot);
>  
>  static struct vfio_group *vfio_iommu_find_iommu_group(struct vfio_iommu *iommu,
> @@ -949,6 +952,7 @@ static void vfio_remove_dma(struct vfio_iommu *iommu, struct vfio_dma *dma)
>  	vfio_unlink_dma(iommu, dma);
>  	put_task_struct(dma->task);
>  	vfio_dma_bitmap_free(dma);
> +	kfree(dma->iommu_mapped_bitmap);
>  	kfree(dma);
>  	iommu->dma_avail++;
>  }
> @@ -1354,6 +1358,14 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
>  		goto out_unlock;
>  	}
>  
> +	dma->iommu_mapped_bitmap = kvzalloc(IOMMU_MAPPED_BITMAP_BYTES(size / PAGE_SIZE),
> +					    GFP_KERNEL);

This is a lot of bloat for all the platforms that don't support this
feature.  Thanks,

Alex

> +	if (!dma->iommu_mapped_bitmap) {
> +		ret = -ENOMEM;
> +		kfree(dma);
> +		goto out_unlock;
> +	}
> +
>  	iommu->dma_avail--;
>  	dma->iova = iova;
>  	dma->vaddr = vaddr;