linux-kernel - Re: [RFC PATCH v2 04/10] iommu/riscv: add iotlb_sync

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Date: Sat, 15 Jun 2024 11:14:47 +0800
From: Baolu Lu <baolu.lu@...ux.intel.com>
To: Zong Li <zong.li@...ive.com>, joro@...tes.org, will@...nel.org,
 robin.murphy@....com, tjeznach@...osinc.com, paul.walmsley@...ive.com,
 palmer@...belt.com, aou@...s.berkeley.edu, jgg@...pe.ca,
 kevin.tian@...el.com, linux-kernel@...r.kernel.org, iommu@...ts.linux.dev,
 linux-riscv@...ts.infradead.org
Cc: baolu.lu@...ux.intel.com
Subject: Re: [RFC PATCH v2 04/10] iommu/riscv: add iotlb_sync_map operation
 support

On 6/14/24 10:21 PM, Zong Li wrote:
> Add iotlb_sync_map operation for flush IOTLB. Software must
> flush the IOTLB after each page table.
> 
> Signed-off-by: Zong Li<zong.li@...ive.com>
> ---
>   drivers/iommu/riscv/Makefile |  1 +
>   drivers/iommu/riscv/iommu.c  | 11 +++++++++++
>   2 files changed, 12 insertions(+)
> 
> diff --git a/drivers/iommu/riscv/Makefile b/drivers/iommu/riscv/Makefile
> index d36625a1fd08..f02ce6ebfbd0 100644
> --- a/drivers/iommu/riscv/Makefile
> +++ b/drivers/iommu/riscv/Makefile
> @@ -1,3 +1,4 @@
>   # SPDX-License-Identifier: GPL-2.0-only
>   obj-$(CONFIG_RISCV_IOMMU) += iommu.o iommu-platform.o iommu-pmu.o
>   obj-$(CONFIG_RISCV_IOMMU_PCI) += iommu-pci.o
> +obj-$(CONFIG_SIFIVE_IOMMU) += iommu-sifive.o
> diff --git a/drivers/iommu/riscv/iommu.c b/drivers/iommu/riscv/iommu.c
> index 9aeb4b20c145..df7aeb2571ae 100644
> --- a/drivers/iommu/riscv/iommu.c
> +++ b/drivers/iommu/riscv/iommu.c
> @@ -1115,6 +1115,16 @@ static void riscv_iommu_iotlb_sync(struct iommu_domain *iommu_domain,
>   	riscv_iommu_iotlb_inval(domain, gather->start, gather->end);
>   }
>   
> +static int riscv_iommu_iotlb_sync_map(struct iommu_domain *iommu_domain,
> +				      unsigned long iova, size_t size)
> +{
> +	struct riscv_iommu_domain *domain = iommu_domain_to_riscv(iommu_domain);
> +
> +	riscv_iommu_iotlb_inval(domain, iova, iova + size - 1);

Does the RISC-V IOMMU architecture always cache the non-present or
erroneous translation entries? If so, can you please provide more
context in the commit message?

If not, why do you want to flush the cache when building a new
translation?

Best regards,
baolu