linux-kernel - Re: [PATCH v2 2/2] vfio iommu: Fix size argument to vfio_find_dma() in pin_pages/unpin

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Date:   Tue, 6 Dec 2016 10:40:01 -0700
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Kirti Wankhede <kwankhede@...dia.com>
Cc:     <pbonzini@...hat.com>, <kraxel@...hat.com>, <cjia@...dia.com>,
        <qemu-devel@...gnu.org>, <kvm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] vfio iommu: Fix size argument to vfio_find_dma()
 in pin_pages/unpin_pages

On Tue, 6 Dec 2016 22:43:45 +0530
Kirti Wankhede <kwankhede@...dia.com> wrote:

> vfio_dma keeps track of address range from (dma->iova + 0) to
> (dma->iova + dma->size - 1), while vfio_find_dma() search logic looks for
> range from (dma->iova + 1) to (dma->iova + dma->size).

Also not true as described in reply to 1/2.

> In vfio_find_dma(), when the start address is equal to dma->iova and size
> is 0, check for the end of search range makes it to take wrong side of
> RB-tree. That fails the search even though the address is present in
> mapped dma ranges.
> In functions pin_pages and unpin_pages, the iova which is being searched
> is base address of page to be pinned or unpinned. So here size should be
> set to PAGE_SIZE, as argument to vfio_find_dma.
> 
> Signed-off-by: Kirti Wankhede <kwankhede@...dia.com>
> Signed-off-by: Neo Jia <cjia@...dia.com>
> ---
>  drivers/vfio/vfio_iommu_type1.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 8e9e94ccb2ff..023fba7b8d5a 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -581,7 +581,7 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data,
>  		struct vfio_pfn *vpfn;
>  
>  		iova = user_pfn[i] << PAGE_SHIFT;
> -		dma = vfio_find_dma(iommu, iova, 0);
> +		dma = vfio_find_dma(iommu, iova, PAGE_SIZE);
>  		if (!dma) {
>  			ret = -EINVAL;
>  			goto pin_unwind;
> @@ -622,7 +622,7 @@ pin_unwind:
>  		dma_addr_t iova;
>  
>  		iova = user_pfn[j] << PAGE_SHIFT;
> -		dma = vfio_find_dma(iommu, iova, 0);
> +		dma = vfio_find_dma(iommu, iova, PAGE_SIZE);
>  		vfio_unpin_page_external(dma, iova, do_accounting);
>  		phys_pfn[j] = 0;
>  	}
> @@ -659,7 +659,7 @@ static int vfio_iommu_type1_unpin_pages(void *iommu_data,
>  		dma_addr_t iova;
>  
>  		iova = user_pfn[i] << PAGE_SHIFT;
> -		dma = vfio_find_dma(iommu, iova, 0);
> +		dma = vfio_find_dma(iommu, iova, PAGE_SIZE);
>  		if (!dma)
>  			goto unpin_exit;
>  		vfio_unpin_page_external(dma, iova, do_accounting);