Re: [RFC PATCH v2 04/10] iommu/riscv: add iotlb_sync_map operation support

[Baolu Lu <baolu.lu@linux.intel.com>]

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@sifive.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