linux-kernel - Re: [PATCH v2] iommu: Defer the early return in arm_(v7s/lpae)

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Message-ID: <ebf1f2cc-b6bf-90b2-8a1c-535fc242d6da@arm.com>
Date:   Tue, 8 Dec 2020 14:20:27 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Keqian Zhu <zhukeqian1@...wei.com>, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        iommu@...ts.linux-foundation.org
Cc:     Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
        Joerg Roedel <joro@...tes.org>,
        Catalin Marinas <catalin.marinas@....com>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexios Zavras <alexios.zavras@...el.com>,
        wanghaibin.wang@...wei.com, jiangkunkun@...wei.com
Subject: Re: [PATCH v2] iommu: Defer the early return in arm_(v7s/lpae)_map

On 2020-12-07 11:57, Keqian Zhu wrote:
> Although handling a mapping request with no permissions is a
> trivial no-op, defer the early return until after the size/range
> checks so that we are consistent with other mapping requests.

Reviewed-by: Robin Murphy <robin.murphy@....com>

> Signed-off-by: Keqian Zhu <zhukeqian1@...wei.com>
> ---
>   drivers/iommu/io-pgtable-arm-v7s.c | 8 ++++----
>   drivers/iommu/io-pgtable-arm.c     | 8 ++++----
>   2 files changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/iommu/io-pgtable-arm-v7s.c b/drivers/iommu/io-pgtable-arm-v7s.c
> index a688f22cbe3b..359b96b0fa3e 100644
> --- a/drivers/iommu/io-pgtable-arm-v7s.c
> +++ b/drivers/iommu/io-pgtable-arm-v7s.c
> @@ -522,14 +522,14 @@ static int arm_v7s_map(struct io_pgtable_ops *ops, unsigned long iova,
>   	struct io_pgtable *iop = &data->iop;
>   	int ret;
>   
> -	/* If no access, then nothing to do */
> -	if (!(prot & (IOMMU_READ | IOMMU_WRITE)))
> -		return 0;
> -
>   	if (WARN_ON(iova >= (1ULL << data->iop.cfg.ias) ||
>   		    paddr >= (1ULL << data->iop.cfg.oas)))
>   		return -ERANGE;
>   
> +	/* If no access, then nothing to do */
> +	if (!(prot & (IOMMU_READ | IOMMU_WRITE)))
> +		return 0;
> +
>   	ret = __arm_v7s_map(data, iova, paddr, size, prot, 1, data->pgd, gfp);
>   	/*
>   	 * Synchronise all PTE updates for the new mapping before there's
> diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
> index a7a9bc08dcd1..8ade72adab31 100644
> --- a/drivers/iommu/io-pgtable-arm.c
> +++ b/drivers/iommu/io-pgtable-arm.c
> @@ -444,10 +444,6 @@ static int arm_lpae_map(struct io_pgtable_ops *ops, unsigned long iova,
>   	arm_lpae_iopte prot;
>   	long iaext = (s64)iova >> cfg->ias;
>   
> -	/* If no access, then nothing to do */
> -	if (!(iommu_prot & (IOMMU_READ | IOMMU_WRITE)))
> -		return 0;
> -
>   	if (WARN_ON(!size || (size & cfg->pgsize_bitmap) != size))
>   		return -EINVAL;
>   
> @@ -456,6 +452,10 @@ static int arm_lpae_map(struct io_pgtable_ops *ops, unsigned long iova,
>   	if (WARN_ON(iaext || paddr >> cfg->oas))
>   		return -ERANGE;
>   
> +	/* If no access, then nothing to do */
> +	if (!(iommu_prot & (IOMMU_READ | IOMMU_WRITE)))
> +		return 0;
> +
>   	prot = arm_lpae_prot_to_pte(data, iommu_prot);
>   	ret = __arm_lpae_map(data, iova, paddr, size, prot, lvl, ptep, gfp);
>   	/*
>