linux-kernel - Re: [PATCH 5/6] vfio/iommu_type1: Drop parameter "pgsize" of vfio_iova_dirty

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Date:   Fri, 15 Jan 2021 16:39:26 -0700
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Keqian Zhu <zhukeqian1@...wei.com>
Cc:     <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <iommu@...ts.linux-foundation.org>, <kvm@...r.kernel.org>,
        <kvmarm@...ts.cs.columbia.edu>, Cornelia Huck <cohuck@...hat.com>,
        Will Deacon <will@...nel.org>, "Marc Zyngier" <maz@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Mark Rutland <mark.rutland@....com>,
        James Morse <james.morse@....com>,
        Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>,
        "Daniel Lezcano" <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexios Zavras <alexios.zavras@...el.com>,
        <wanghaibin.wang@...wei.com>, <jiangkunkun@...wei.com>
Subject: Re: [PATCH 5/6] vfio/iommu_type1: Drop parameter "pgsize" of
 vfio_iova_dirty_bitmap

On Thu, 7 Jan 2021 12:44:00 +0800
Keqian Zhu <zhukeqian1@...wei.com> wrote:

> We always use the smallest supported page size of vfio_iommu as
> pgsize. Remove parameter "pgsize" of vfio_iova_dirty_bitmap.
> 
> Signed-off-by: Keqian Zhu <zhukeqian1@...wei.com>
> ---
>  drivers/vfio/vfio_iommu_type1.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 080c05b129ee..82649a040148 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -1015,11 +1015,12 @@ static int update_user_bitmap(u64 __user *bitmap, struct vfio_iommu *iommu,
>  }
>  
>  static int vfio_iova_dirty_bitmap(u64 __user *bitmap, struct vfio_iommu *iommu,
> -				  dma_addr_t iova, size_t size, size_t pgsize)
> +				  dma_addr_t iova, size_t size)
>  {
>  	struct vfio_dma *dma;
>  	struct rb_node *n;
> -	unsigned long pgshift = __ffs(pgsize);
> +	unsigned long pgshift = __ffs(iommu->pgsize_bitmap);
> +	size_t pgsize = (size_t)1 << pgshift;
>  	int ret;
>  
>  	/*
> @@ -2824,8 +2825,7 @@ static int vfio_iommu_type1_dirty_pages(struct vfio_iommu *iommu,
>  		if (iommu->dirty_page_tracking)
>  			ret = vfio_iova_dirty_bitmap(range.bitmap.data,
>  						     iommu, range.iova,
> -						     range.size,
> -						     range.bitmap.pgsize);
> +						     range.size);
>  		else
>  			ret = -EINVAL;
>  out_unlock:

In this case the caller has actually already calculated both pgsize and
pgshift, the better optimization would be to pass both rather than
recalculate.  Thanks,

Alex