linux-kernel - Re: [PATCH v3 1/1] iommu: Add config option to set lazy mode as default

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Date:   Sat, 30 Mar 2019 18:43:15 +0800
From:   "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>
To:     Jean-Philippe Brucker <jean-philippe.brucker@....com>,
        John Garry <john.garry@...wei.com>,
        Robin Murphy <robin.murphy@....com>,
        Will Deacon <will.deacon@....com>,
        Joerg Roedel <joro@...tes.org>,
        iommu <iommu@...ts.linux-foundation.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
CC:     S390 <linux-s390@...r.kernel.org>,
        Hanjun Guo <guohanjun@...wei.com>
Subject: Re: [PATCH v3 1/1] iommu: Add config option to set lazy mode as
 default



On 2019/3/29 10:54, Zhen Lei wrote:
> This allows the default behaviour to be controlled by a kernel config
> option instead of changing the command line for the kernel to include
> "iommu.strict=0" on ARM64 where this is desired.
> 
> This is similar to CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
> 
> Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>
> ---
>  arch/s390/pci/pci_dma.c        |  4 ++++
>  drivers/iommu/Kconfig          | 15 +++++++++++++++
>  drivers/iommu/amd_iommu_init.c |  6 +++++-
>  drivers/iommu/intel-iommu.c    |  4 ++++
>  drivers/iommu/iommu.c          |  5 +++++
>  5 files changed, 33 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/s390/pci/pci_dma.c b/arch/s390/pci/pci_dma.c
> index 9e52d1527f71495..d05e8c3820793c5 100644
> --- a/arch/s390/pci/pci_dma.c
> +++ b/arch/s390/pci/pci_dma.c
> @@ -17,7 +17,11 @@
>  
>  static struct kmem_cache *dma_region_table_cache;
>  static struct kmem_cache *dma_page_table_cache;
> +#ifdef CONFIG_IOMMU_DMA_DEFAULT_LAZY_MODE
>  static int s390_iommu_strict;
> +#else
> +static int s390_iommu_strict = 1;
> +#endif
>  
>  static int zpci_refresh_global(struct zpci_dev *zdev)
>  {
> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> index 6f07f3b21816c64..ed5206a2d316599 100644
> --- a/drivers/iommu/Kconfig
> +++ b/drivers/iommu/Kconfig
> @@ -85,6 +85,21 @@ config IOMMU_DEFAULT_PASSTHROUGH
>  
>  	  If unsure, say N here.
>  
> +config IOMMU_DMA_DEFAULT_LAZY_MODE
> +	bool "IOMMU DMA use lazy mode to flush IOTLB and free IOVA"
> +	depends on IOMMU_API
> +	default y
Hi Robin：

   Should I change to:
+  default y if !(ARM_SMMU || ARM_SMMU_V3)

> +	help
> +	  Support lazy mode, where for every IOMMU DMA unmap operation, the
> +	  flush operation of IOTLB and the free operation of IOVA are deferred.
> +	  They are only guaranteed to be done before the related IOVA will be
> +	  reused. Removing the need to pass in kernel parameters through
> +	  command line. For example, iommu.strict=0 on ARM64. If this is
> +	  enabled, you can still disable with kernel parameters, such as
> +	  iommu.strict=1 depending on the architecture.
> +
> +	  If unsure, say N here.
> +
>  config OF_IOMMU
>         def_bool y
>         depends on OF && IOMMU_API
> diff --git a/drivers/iommu/amd_iommu_init.c b/drivers/iommu/amd_iommu_init.c
> index f773792d77fd533..a30805c2f77199c 100644
> --- a/drivers/iommu/amd_iommu_init.c
> +++ b/drivers/iommu/amd_iommu_init.c
> @@ -166,7 +166,11 @@ struct ivmd_header {
>  					   to handle */
>  LIST_HEAD(amd_iommu_unity_map);		/* a list of required unity mappings
>  					   we find in ACPI */
> -bool amd_iommu_unmap_flush;		/* if true, flush on every unmap */
> +#ifdef CONFIG_IOMMU_DMA_DEFAULT_LAZY_MODE
> +bool amd_iommu_unmap_flush;
> +#else
> +bool amd_iommu_unmap_flush = true;	/* flush on every unmap */
> +#endif
>  
>  LIST_HEAD(amd_iommu_list);		/* list of all AMD IOMMUs in the
>  					   system */
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index 28cb713d728ceef..560191a9342b2b8 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -362,7 +362,11 @@ static int domain_detach_iommu(struct dmar_domain *domain,
>  
>  static int dmar_map_gfx = 1;
>  static int dmar_forcedac;
> +#ifdef CONFIG_IOMMU_DMA_DEFAULT_LAZY_MODE
>  static int intel_iommu_strict;
> +#else
> +static int intel_iommu_strict = 1;
> +#endif
>  static int intel_iommu_superpage = 1;
>  static int intel_iommu_sm;
>  static int iommu_identity_mapping;
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 33a982e33716369..5acb98e79b5b32d 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -43,7 +43,12 @@
>  #else
>  static unsigned int iommu_def_domain_type = IOMMU_DOMAIN_DMA;
>  #endif
> +
> +#ifdef CONFIG_IOMMU_DMA_DEFAULT_LAZY_MODE
> +static bool iommu_dma_strict __read_mostly;
> +#else
>  static bool iommu_dma_strict __read_mostly = true;
> +#endif
>  
>  struct iommu_callback_data {
>  	const struct iommu_ops *ops;
> 

-- 
Thanks!
BestRegards