linux-kernel - Re: [PATCH v1 1/1] iommu/vt-d: Don't cast parameter in for_each_set

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Date:   Thu, 10 Feb 2022 09:19:50 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Joerg Roedel <jroedel@...e.de>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Cc:     baolu.lu@...ux.intel.com, David Woodhouse <dwmw2@...radead.org>,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>
Subject: Re: [PATCH v1 1/1] iommu/vt-d: Don't cast parameter in
 for_each_set_bit()

Hi Andy,

On 2/10/22 1:49 AM, Andy Shevchenko wrote:
> While in this particular case it would not be a (critical) issue,
> the pattern itself is bad and error prone in case the location
> of the parameter is changed.
> 
> Don't cast parameter to unsigned long pointer in for_each_set_bit().
> Instead copy to a local variable on stack of a proper type and use.
> 
> Fixes: 6ee1b77ba3ac ("iommu/vt-d: Add svm/sva invalidate function")
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
>   drivers/iommu/intel/iommu.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index 92fea3fbbb11..777e81b8f4f5 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -4973,6 +4973,7 @@ intel_iommu_sva_invalidate(struct iommu_domain *domain, struct device *dev,
>   	struct dmar_domain *dmar_domain = to_dmar_domain(domain);
>   	struct device_domain_info *info;
>   	struct intel_iommu *iommu;
> +	unsigned long cache_bits;
>   	unsigned long flags;
>   	int cache_type;
>   	u8 bus, devfn;
> @@ -5008,9 +5009,8 @@ intel_iommu_sva_invalidate(struct iommu_domain *domain, struct device *dev,
>   		size = to_vtd_size(inv_info->granu.addr_info.granule_size,
>   				   inv_info->granu.addr_info.nb_granules);
>   
> -	for_each_set_bit(cache_type,
> -			 (unsigned long *)&inv_info->cache,
> -			 IOMMU_CACHE_INV_TYPE_NR) {
> +	cache_bits = inv_info->cache;
> +	for_each_set_bit(cache_type, &cache_bits, IOMMU_CACHE_INV_TYPE_NR) {
>   		int granu = 0;
>   		u64 pasid = 0;
>   		u64 addr = 0;

Thanks for your patch. The function that you are changing becomes dead
code (nobody uses it and there's no plan to use it anymore) now. I
already have a patch to remove this function.

Best regards,
baolu