linux-kernel - Re: [PATCH v5 1/2] iommu/io-pgtable-arm-v7s: Add a quirk to allow pgtable PA up to 35bit

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Date:   Thu, 19 May 2022 14:27:56 +0800
From:   Miles Chen <miles.chen@...iatek.com>
To:     <yf.wang@...iatek.com>
CC:     <Libo.Kang@...iatek.com>, <Yong.Wu@...iatek.com>,
        <iommu@...ts.linux-foundation.org>, <isaacm@...eaurora.org>,
        <joro@...tes.org>, <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-mediatek@...ts.infradead.org>, <matthias.bgg@...il.com>,
        <ning.li@...iatek.com>, <quic_c_gdjako@...cinc.com>,
        <robin.murphy@....com>, <sven@...npeter.dev>, <will@...nel.org>,
        <wsd_upstream@...iatek.com>
Subject: Re: [PATCH v5 1/2] iommu/io-pgtable-arm-v7s: Add a quirk to allow pgtable PA up to 35bit

Hi Yunfei,

> The calling to kmem_cache_alloc for level 2 pgtable allocation may run
> in atomic context, and it fails sometimes when DMA32 zone runs out of
> memory.
> 
> Since Mediatek IOMMU hardware support at most 35bit PA in pgtable,
> so add a quirk to allow the PA of pgtables support up to bit35.
> 
> Signed-off-by: Ning Li <ning.li@...iatek.com>
> Signed-off-by: Yunfei Wang <yf.wang@...iatek.com>
> ---
>  drivers/iommu/io-pgtable-arm-v7s.c | 56 ++++++++++++++++++++++--------
>  include/linux/io-pgtable.h         | 15 +++++---
>  2 files changed, 52 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/iommu/io-pgtable-arm-v7s.c b/drivers/iommu/io-pgtable-arm-v7s.c

...snip...

> +	gfp_t gfp_l1 = __GFP_ZERO | ARM_V7S_TABLE_GFP_DMA;
>  	struct io_pgtable_cfg *cfg = &data->iop.cfg;
>  	struct device *dev = cfg->iommu_dev;
>  	phys_addr_t phys;
> @@ -241,9 +251,11 @@ static void *__arm_v7s_alloc_table(int lvl, gfp_t gfp,
>  	size_t size = ARM_V7S_TABLE_SIZE(lvl, cfg);
>  	void *table = NULL;
>  
> +	if (cfg->quirks & IO_PGTABLE_QUIRK_ARM_MTK_TTBR_EXT)
> +		gfp_l1 = __GFP_ZERO;

__GFP_ZERO is an action modifier, if we do not want
ARM_V7S_TABLE_GFP_DMA (GFP_DMA/GFP_DMA32), use gfp_l1 = (GFP_KERNEL | __GFP_ZERO)

thanks,
Miles
> +
>  	if (lvl == 1)
> -		table = (void *)__get_free_pages(
> -			__GFP_ZERO | ARM_V7S_TABLE_GFP_DMA, get_order(size));
> +		table = (void *)__get_free_pages(gfp_l1, get_order(size));
>  	else if (lvl == 2)
>  		table = kmem_cache_zalloc(data->l2_tables, gfp);
>