linux-kernel - Re: [PATCH v3 08/24] iommu/io-pgtable-arm-v7s: Use ias to check the valid iova in unmap

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Message-ID: <20201023111740.GA20933@willie-the-truck>
Date:   Fri, 23 Oct 2020 12:17:41 +0100
From:   Will Deacon <will@...nel.org>
To:     Yong Wu <yong.wu@...iatek.com>
Cc:     Joerg Roedel <joro@...tes.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Evan Green <evgreen@...omium.org>,
        Tomasz Figa <tfiga@...gle.com>,
        linux-mediatek@...ts.infradead.org, srv_heupstream@...iatek.com,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        iommu@...ts.linux-foundation.org, youlin.pei@...iatek.com,
        Nicolas Boichat <drinkcat@...omium.org>, anan.sun@...iatek.com,
        chao.hao@...iatek.com, ming-fan.chen@...iatek.com,
        Greg Kroah-Hartman <gregkh@...gle.com>, kernel-team@...roid.com
Subject: Re: [PATCH v3 08/24] iommu/io-pgtable-arm-v7s: Use ias to check the
 valid iova in unmap

On Wed, Sep 30, 2020 at 03:06:31PM +0800, Yong Wu wrote:
> Use the ias for the valid iova checking in arm_v7s_unmap. This is a
> preparing patch for supporting iova 34bit for MediaTek.
> BTW, change the ias/oas checking format in arm_v7s_map.
> 
> Signed-off-by: Yong Wu <yong.wu@...iatek.com>
> ---
>  drivers/iommu/io-pgtable-arm-v7s.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iommu/io-pgtable-arm-v7s.c b/drivers/iommu/io-pgtable-arm-v7s.c
> index a688f22cbe3b..4c9d8dccfc5a 100644
> --- a/drivers/iommu/io-pgtable-arm-v7s.c
> +++ b/drivers/iommu/io-pgtable-arm-v7s.c
> @@ -526,8 +526,7 @@ static int arm_v7s_map(struct io_pgtable_ops *ops, unsigned long iova,
>  	if (!(prot & (IOMMU_READ | IOMMU_WRITE)))
>  		return 0;
>  
> -	if (WARN_ON(iova >= (1ULL << data->iop.cfg.ias) ||
> -		    paddr >= (1ULL << data->iop.cfg.oas)))
> +	if (WARN_ON(iova >> data->iop.cfg.ias || paddr >> data->iop.cfg.oas))
>  		return -ERANGE;

As discussed when reviewing these for Android, please leave this code as-is.

>  
>  	ret = __arm_v7s_map(data, iova, paddr, size, prot, 1, data->pgd, gfp);
> @@ -717,7 +716,7 @@ static size_t arm_v7s_unmap(struct io_pgtable_ops *ops, unsigned long iova,
>  {
>  	struct arm_v7s_io_pgtable *data = io_pgtable_ops_to_data(ops);
>  
> -	if (WARN_ON(upper_32_bits(iova)))
> +	if (WARN_ON(iova >> data->iop.cfg.ias))
>  		return 0;

And avoid the UB here for 32-bit machines by comparing with 1ULL <<
iop.cfg.ias instead.

Thanks,

Will