Re: [PATCH v4 1/5] dma: swiotlb: Centralize default pool policy selection

From: Catalin Marinas <catalin.marinas@arm.com>
To: "Aneesh Kumar K.V (Arm)" <aneesh.kumar@kernel.org>
Cc: iommu@lists.linux.dev, linux-kernel@vger.kernel.org,
	Robin Murphy <robin.murphy@arm.com>,
	Marek Szyprowski <m.szyprowski@samsung.com>,
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Subject: Re: [PATCH v4 1/5] dma: swiotlb: Centralize default pool policy selection
Date: Thu, 17 Sep 2026 15:47:37 +0100	[thread overview]
Message-ID: <aqv9icxsfN3PLErN@arm.com> (raw)
In-Reply-To: <20260914070135.313337-2-aneesh.kumar@kernel.org>

On Mon, Sep 14, 2026 at 12:31:30PM +0530, Aneesh Kumar K.V (Arm) wrote:
> diff --git a/arch/x86/include/asm/iommu.h b/arch/x86/include/asm/iommu.h
> index 3be2451e7bc8..22c8190fe34d 100644
> --- a/arch/x86/include/asm/iommu.h
> +++ b/arch/x86/include/asm/iommu.h
> @@ -14,8 +14,10 @@ extern bool amd_iommu_snp_en;
>  
>  #ifdef CONFIG_SWIOTLB
>  extern bool x86_swiotlb_enable;
> +extern unsigned int x86_swiotlb_flags;
>  #else
>  #define x86_swiotlb_enable false
> +#define x86_swiotlb_flags 0
>  #endif
>  
>  /* 10 seconds */
> diff --git a/arch/x86/kernel/amd_gart_64.c b/arch/x86/kernel/amd_gart_64.c
> index b5f1f031d45b..d0fbc0271e43 100644
> --- a/arch/x86/kernel/amd_gart_64.c
> +++ b/arch/x86/kernel/amd_gart_64.c
> @@ -814,6 +814,7 @@ int __init gart_iommu_init(void)
>  	dma_ops = &gart_dma_ops;
>  	x86_platform.iommu_shutdown = gart_iommu_shutdown;
>  	x86_swiotlb_enable = false;
> +	x86_swiotlb_flags = 0;

I don't think the flags are still read anywhere after this function.
gart_iommu_init() is called long after swiotlb_init(). So you can drop
this and make x86_swiotlb_flags static in pci-dma.c.

With this:

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>