Re: [RFC PATCH v4 09/15] iommu/io-pgtable-arm: Prepare PTE methods for handling multiple entries

From: Will Deacon <will@kernel.org>
To: "Isaac J. Manjarres" <isaacm@codeaurora.org>
Cc: iommu@lists.linux-foundation.org,
	linux-arm-kernel@lists.infradead.org, baolu.lu@linux.intel.com,
	robin.murphy@arm.com, pratikp@codeaurora.org
Subject: Re: [RFC PATCH v4 09/15] iommu/io-pgtable-arm: Prepare PTE methods for handling multiple entries
Date: Thu, 8 Apr 2021 14:59:26 +0100	[thread overview]
Message-ID: <20210408135925.GC17998@willie-the-truck> (raw)
In-Reply-To: <20210408045241.27316-10-isaacm@codeaurora.org>

On Wed, Apr 07, 2021 at 09:52:35PM -0700, Isaac J. Manjarres wrote:
> The PTE methods currently operate on a single entry. In preparation
> for manipulating multiple PTEs in one map or unmap call, allow them
> to handle multiple PTEs.
> 
> Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>
> Suggested-by: Robin Murphy <robin.murphy@arm.com>
> ---
>  drivers/iommu/io-pgtable-arm.c | 78 +++++++++++++++++++---------------
>  1 file changed, 44 insertions(+), 34 deletions(-)
> 
> diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
> index 87def58e79b5..ea66b10c04c4 100644
> --- a/drivers/iommu/io-pgtable-arm.c
> +++ b/drivers/iommu/io-pgtable-arm.c
> @@ -232,20 +232,23 @@ static void __arm_lpae_free_pages(void *pages, size_t size,
>  	free_pages((unsigned long)pages, get_order(size));
>  }
>  
> -static void __arm_lpae_sync_pte(arm_lpae_iopte *ptep,
> +static void __arm_lpae_sync_pte(arm_lpae_iopte *ptep, int num_entries,
>  				struct io_pgtable_cfg *cfg)
>  {
>  	dma_sync_single_for_device(cfg->iommu_dev, __arm_lpae_dma_addr(ptep),
> -				   sizeof(*ptep), DMA_TO_DEVICE);
> +				   sizeof(*ptep) * num_entries, DMA_TO_DEVICE);
>  }

Have you tested this with CONFIG_DMA_API_DEBUG=y? I _think_ it should be
ok as long as we don't attempt to sync across a page boundary, but it would
be good to give it a spin just to check.

Will

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