linux-kernel - Re: [PATCH 4/6] vfio/iommu_type1: Drop parameter "pgsize" of vfio_dma_bitmap_alloc

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Message-ID: <20210115163738.112f0c34@omen.home.shazbot.org>
Date:   Fri, 15 Jan 2021 16:37:38 -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 4/6] vfio/iommu_type1: Drop parameter "pgsize" of
 vfio_dma_bitmap_alloc_all

On Thu, 7 Jan 2021 12:43:59 +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_dma_bitmap_alloc_all.
> 
> Signed-off-by: Keqian Zhu <zhukeqian1@...wei.com>
> ---
>  drivers/vfio/vfio_iommu_type1.c | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index b596c482487b..080c05b129ee 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -236,9 +236,10 @@ static void vfio_dma_populate_bitmap(struct vfio_dma *dma, size_t pgsize)
>  	}
>  }
>  
> -static int vfio_dma_bitmap_alloc_all(struct vfio_iommu *iommu, size_t pgsize)
> +static int vfio_dma_bitmap_alloc_all(struct vfio_iommu *iommu)
>  {
>  	struct rb_node *n;
> +	size_t pgsize = (size_t)1 << __ffs(iommu->pgsize_bitmap);
>  
>  	for (n = rb_first(&iommu->dma_list); n; n = rb_next(n)) {
>  		struct vfio_dma *dma = rb_entry(n, struct vfio_dma, node);
> @@ -2761,12 +2762,9 @@ static int vfio_iommu_type1_dirty_pages(struct vfio_iommu *iommu,
>  		return -EINVAL;
>  
>  	if (dirty.flags & VFIO_IOMMU_DIRTY_PAGES_FLAG_START) {
> -		size_t pgsize;
> -
>  		mutex_lock(&iommu->lock);
> -		pgsize = 1 << __ffs(iommu->pgsize_bitmap);
>  		if (!iommu->dirty_page_tracking) {
> -			ret = vfio_dma_bitmap_alloc_all(iommu, pgsize);
> +			ret = vfio_dma_bitmap_alloc_all(iommu);
>  			if (!ret)
>  				iommu->dirty_page_tracking = true;
>  		}

This just moves the same calculation from one place to another, what's
the point?  Thanks,

Alex