linux-kernel - Re: [PATCH 5.10 337/663] iommu: Move iotlb_sync_map out from __iommu

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Message-ID: <20210304084329.GA25188@amd>
Date:   Thu, 4 Mar 2021 09:43:29 +0100
From:   Pavel Machek <pavel@....cz>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Yong Wu <yong.wu@...iatek.com>,
        Robin Murphy <robin.murphy@....com>,
        Will Deacon <will@...nel.org>, Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 5.10 337/663] iommu: Move iotlb_sync_map out from
 __iommu_map

Hi!

> [ Upstream commit d8c1df02ac7f2c802a9b2afc0f5c888c4217f1d5 ]
> 
> In the end of __iommu_map, It alway call iotlb_sync_map.
> 
> This patch moves iotlb_sync_map out from __iommu_map since it is
> unnecessary to call this for each sg segment especially iotlb_sync_map
> is flush tlb all currently. Add a little helper _iommu_map for this.

> Signed-off-by: Sasha Levin <sashal@...nel.org>

AFAICT this is slight performance optimalization, not a bugfix. It
actually introduces a bug, fixed by the next patch. I'd preffer not to
have it in stable.

Best regards,
								Pavel

> @@ -2421,18 +2418,31 @@ static int __iommu_map(struct iommu_domain *domain, unsigned long iova,
>  
> +static int _iommu_map(struct iommu_domain *domain, unsigned long iova,
> +		      phys_addr_t paddr, size_t size, int prot, gfp_t gfp)
> +{
> +	const struct iommu_ops *ops = domain->ops;
> +	int ret;
> +
> +	ret = __iommu_map(domain, iova, paddr, size, prot, GFP_KERNEL);
> +	if (ret == 0 && ops->iotlb_sync_map)
> +		ops->iotlb_sync_map(domain);
> +
> +	return ret;
> +}

-- 
http://www.livejournal.com/~pavelmachek

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