diff mbox series

[v2,20/24] iommu: Merge strictness and domain type configs

Message ID 992b2952f0b173411c7b6f221dce82e8e082c0b8.1627468310.git.robin.murphy@arm.com (mailing list archive)
State New, archived
Headers show
Series iommu: Refactor DMA domain strictness | expand

Commit Message

Robin Murphy July 28, 2021, 3:58 p.m. UTC 
To parallel the sysfs behaviour, merge the new build-time option
for DMA domain strictness into the default domain type choice.

Suggested-by: Joerg Roedel <joro@8bytes.org>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---
 drivers/iommu/Kconfig | 80 +++++++++++++++++++++----------------------
 drivers/iommu/iommu.c |  2 +-
 2 files changed, 41 insertions(+), 41 deletions(-)

Comments

Baolu Lu July 30, 2021, 6:10 a.m. UTC | #1 
On 7/28/21 11:58 PM, Robin Murphy wrote:
> To parallel the sysfs behaviour, merge the new build-time option
> for DMA domain strictness into the default domain type choice.
> 
> Suggested-by: Joerg Roedel <joro@8bytes.org>
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
> ---
>   drivers/iommu/Kconfig | 80 +++++++++++++++++++++----------------------
>   drivers/iommu/iommu.c |  2 +-
>   2 files changed, 41 insertions(+), 41 deletions(-)
> 
> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> index c84da8205be7..6e06f876d75a 100644
> --- a/drivers/iommu/Kconfig
> +++ b/drivers/iommu/Kconfig
> @@ -79,55 +79,55 @@ config IOMMU_DEBUGFS
>   	  debug/iommu directory, and then populate a subdirectory with
>   	  entries as required.
>   
> -config IOMMU_DEFAULT_PASSTHROUGH
> -	bool "IOMMU passthrough by default"
> -	depends on IOMMU_API
> -	help
> -	  Enable passthrough by default, removing the need to pass in
> -	  iommu.passthrough=on or iommu=pt through command line. If this
> -	  is enabled, you can still disable with iommu.passthrough=off
> -	  or iommu=nopt depending on the architecture.
> -
> -	  If unsure, say N here.
> -
>   choice
> -	prompt "IOMMU default DMA IOTLB invalidation mode"
> -	depends on IOMMU_DMA
> -
> -	default IOMMU_DEFAULT_LAZY if (AMD_IOMMU || INTEL_IOMMU)
> -	default IOMMU_DEFAULT_STRICT
> +	prompt "IOMMU default domain type"
> +	depends on IOMMU_API
> +	default IOMMU_DEFAULT_DMA_LAZY if AMD_IOMMU || INTEL_IOMMU
> +	default IOMMU_DEFAULT_DMA_STRICT
>   	help
> -	  This option allows an IOMMU DMA IOTLB invalidation mode to be
> -	  chosen at build time, to override the default mode of each ARCH,
> -	  removing the need to pass in kernel parameters through command line.
> -	  It is still possible to provide common boot params to override this
> -	  config.
> +	  Choose the type of IOMMU domain used to manage DMA API usage by
> +	  device drivers. The options here typically represent different
> +	  levels of tradeoff between robustness/security and performance,
> +	  depending on the IOMMU driver. Not all IOMMUs support all options.
> +	  This choice can be overridden at boot via the command line, and for
> +	  some devices also at runtime via sysfs.
>   
>   	  If unsure, keep the default.
>   
> -config IOMMU_DEFAULT_STRICT
> -	bool "strict"
> +config IOMMU_DEFAULT_DMA_STRICT
> +	bool "Translated - Strict"
>   	help
> -	  For every IOMMU DMA unmap operation, the flush operation of IOTLB and
> -	  the free operation of IOVA are guaranteed to be done in the unmap
> -	  function.
> +	  Trusted devices use translation to restrict their access to only
> +	  DMA-mapped pages, with strict TLB invalidation on unmap. Equivalent
> +	  to passing "iommu.passthrough=0 iommu.strict=1" on the command line.
>   
> -config IOMMU_DEFAULT_LAZY
> -	bool "lazy"
> +	  Untrusted devices always use this mode, with an additional layer of
> +	  bounce-buffering such that they cannot gain access to any unrelated
> +	  data within a mapped page.
> +
> +config IOMMU_DEFAULT_DMA_LAZY
> +	bool "Translated - Lazy"
>   	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.
> +	  Trusted devices use translation to restrict their access to only
> +	  DMA-mapped pages, but with "lazy" batched TLB invalidation. This
> +	  mode allows higher performance with some IOMMUs due to reduced TLB
> +	  flushing, but at the cost of reduced isolation since devices may be
> +	  able to access memory for some time after it has been unmapped.
> +	  Equivalent to passing "iommu.passthrough=0 iommu.strict=0" on the
> +	  command line.
>   
> -	  The isolation provided in this mode is not as secure as STRICT mode,
> -	  such that a vulnerable time window may be created between the DMA
> -	  unmap and the mappings cached in the IOMMU IOTLB or device TLB
> -	  finally being invalidated, where the device could still access the
> -	  memory which has already been unmapped by the device driver.
> -	  However this mode may provide better performance in high throughput
> -	  scenarios, and is still considerably more secure than passthrough
> -	  mode or no IOMMU.
> +	  If this mode is not supported by the IOMMU driver, the effective
> +	  runtime default will fall back to IOMMU_DEFAULT_DMA_STRICT.
> +
> +config IOMMU_DEFAULT_PASSTHROUGH
> +	bool "Passthrough"
> +	help
> +	  Trusted devices are identity-mapped, giving them unrestricted access
> +	  to memory with minimal performance overhead. Equivalent to passing
> +	  "iommu.passthrough=1" (historically "iommu=pt") on the command line.
> +
> +	  If this mode is not supported by the IOMMU driver, the effective
> +	  runtime default will fall back to IOMMU_DEFAULT_DMA_STRICT.
>   
>   endchoice
>   
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 5a08e0806cbb..25c1adc1ec67 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -31,7 +31,7 @@ static struct kset *iommu_group_kset;
>   static DEFINE_IDA(iommu_group_ida);
>   
>   static unsigned int iommu_def_domain_type __read_mostly;
> -static bool iommu_dma_strict __read_mostly = IS_ENABLED(CONFIG_IOMMU_DEFAULT_STRICT);
> +static bool iommu_dma_strict __read_mostly = IS_ENABLED(CONFIG_IOMMU_DEFAULT_DMA_STRICT);
>   static u32 iommu_cmd_line __read_mostly;
>   
>   struct iommu_group {
> 


Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>

Best regards,
baolu
Jean-Philippe Brucker July 30, 2021, 9:29 a.m. UTC | #2 
On Wed, Jul 28, 2021 at 04:58:41PM +0100, Robin Murphy wrote:
> To parallel the sysfs behaviour, merge the new build-time option
> for DMA domain strictness into the default domain type choice.
> 
> Suggested-by: Joerg Roedel <joro@8bytes.org>
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>

kernel-parameters.txt still refers to the old config options

Otherwise
Reviewed-by: Jean-Philippe Brucker <jean-philippe@linaro.org>

> ---
>  drivers/iommu/Kconfig | 80 +++++++++++++++++++++----------------------
>  drivers/iommu/iommu.c |  2 +-
>  2 files changed, 41 insertions(+), 41 deletions(-)
> 
> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> index c84da8205be7..6e06f876d75a 100644
> --- a/drivers/iommu/Kconfig
> +++ b/drivers/iommu/Kconfig
> @@ -79,55 +79,55 @@ config IOMMU_DEBUGFS
>  	  debug/iommu directory, and then populate a subdirectory with
>  	  entries as required.
>  
> -config IOMMU_DEFAULT_PASSTHROUGH
> -	bool "IOMMU passthrough by default"
> -	depends on IOMMU_API
> -	help
> -	  Enable passthrough by default, removing the need to pass in
> -	  iommu.passthrough=on or iommu=pt through command line. If this
> -	  is enabled, you can still disable with iommu.passthrough=off
> -	  or iommu=nopt depending on the architecture.
> -
> -	  If unsure, say N here.
> -
>  choice
> -	prompt "IOMMU default DMA IOTLB invalidation mode"
> -	depends on IOMMU_DMA
> -
> -	default IOMMU_DEFAULT_LAZY if (AMD_IOMMU || INTEL_IOMMU)
> -	default IOMMU_DEFAULT_STRICT
> +	prompt "IOMMU default domain type"
> +	depends on IOMMU_API
> +	default IOMMU_DEFAULT_DMA_LAZY if AMD_IOMMU || INTEL_IOMMU
> +	default IOMMU_DEFAULT_DMA_STRICT
>  	help
> -	  This option allows an IOMMU DMA IOTLB invalidation mode to be
> -	  chosen at build time, to override the default mode of each ARCH,
> -	  removing the need to pass in kernel parameters through command line.
> -	  It is still possible to provide common boot params to override this
> -	  config.
> +	  Choose the type of IOMMU domain used to manage DMA API usage by
> +	  device drivers. The options here typically represent different
> +	  levels of tradeoff between robustness/security and performance,
> +	  depending on the IOMMU driver. Not all IOMMUs support all options.
> +	  This choice can be overridden at boot via the command line, and for
> +	  some devices also at runtime via sysfs.
>  
>  	  If unsure, keep the default.
>  
> -config IOMMU_DEFAULT_STRICT
> -	bool "strict"
> +config IOMMU_DEFAULT_DMA_STRICT
> +	bool "Translated - Strict"
>  	help
> -	  For every IOMMU DMA unmap operation, the flush operation of IOTLB and
> -	  the free operation of IOVA are guaranteed to be done in the unmap
> -	  function.
> +	  Trusted devices use translation to restrict their access to only
> +	  DMA-mapped pages, with strict TLB invalidation on unmap. Equivalent
> +	  to passing "iommu.passthrough=0 iommu.strict=1" on the command line.
>  
> -config IOMMU_DEFAULT_LAZY
> -	bool "lazy"
> +	  Untrusted devices always use this mode, with an additional layer of
> +	  bounce-buffering such that they cannot gain access to any unrelated
> +	  data within a mapped page.
> +
> +config IOMMU_DEFAULT_DMA_LAZY
> +	bool "Translated - Lazy"
>  	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.
> +	  Trusted devices use translation to restrict their access to only
> +	  DMA-mapped pages, but with "lazy" batched TLB invalidation. This
> +	  mode allows higher performance with some IOMMUs due to reduced TLB
> +	  flushing, but at the cost of reduced isolation since devices may be
> +	  able to access memory for some time after it has been unmapped.
> +	  Equivalent to passing "iommu.passthrough=0 iommu.strict=0" on the
> +	  command line.
>  
> -	  The isolation provided in this mode is not as secure as STRICT mode,
> -	  such that a vulnerable time window may be created between the DMA
> -	  unmap and the mappings cached in the IOMMU IOTLB or device TLB
> -	  finally being invalidated, where the device could still access the
> -	  memory which has already been unmapped by the device driver.
> -	  However this mode may provide better performance in high throughput
> -	  scenarios, and is still considerably more secure than passthrough
> -	  mode or no IOMMU.
> +	  If this mode is not supported by the IOMMU driver, the effective
> +	  runtime default will fall back to IOMMU_DEFAULT_DMA_STRICT.
> +
> +config IOMMU_DEFAULT_PASSTHROUGH
> +	bool "Passthrough"
> +	help
> +	  Trusted devices are identity-mapped, giving them unrestricted access
> +	  to memory with minimal performance overhead. Equivalent to passing
> +	  "iommu.passthrough=1" (historically "iommu=pt") on the command line.
> +
> +	  If this mode is not supported by the IOMMU driver, the effective
> +	  runtime default will fall back to IOMMU_DEFAULT_DMA_STRICT.
>  
>  endchoice
>  
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 5a08e0806cbb..25c1adc1ec67 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -31,7 +31,7 @@ static struct kset *iommu_group_kset;
>  static DEFINE_IDA(iommu_group_ida);
>  
>  static unsigned int iommu_def_domain_type __read_mostly;
> -static bool iommu_dma_strict __read_mostly = IS_ENABLED(CONFIG_IOMMU_DEFAULT_STRICT);
> +static bool iommu_dma_strict __read_mostly = IS_ENABLED(CONFIG_IOMMU_DEFAULT_DMA_STRICT);
>  static u32 iommu_cmd_line __read_mostly;
>  
>  struct iommu_group {
> -- 
> 2.25.1
> 
> _______________________________________________
> iommu mailing list
> iommu@lists.linux-foundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/iommu
John Garry July 30, 2021, 9:33 a.m. UTC | #3 
On 28/07/2021 16:58, Robin Murphy wrote:
>   
> -config IOMMU_DEFAULT_LAZY
> -	bool "lazy"
> +	  Untrusted devices always use this mode, with an additional layer of
> +	  bounce-buffering such that they cannot gain access to any unrelated
> +	  data within a mapped page.
> +
> +config IOMMU_DEFAULT_DMA_LAZY
> +	bool "Translated - Lazy"
>   	help

Since these are being renamed, can you update the kernel-parameters.txt:


	iommu.strict=	[ARM64, X86] Configure TLB invalidation behaviour


....
		  DMA unmap operations invalidate IOMMU hardware TLBs
		  synchronously.
		unset - Use value of CONFIG_IOMMU_DEFAULT_{LAZY,STRICT}.

					^^^^^

Thanks
diff mbox series

Patch

diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index c84da8205be7..6e06f876d75a 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -79,55 +79,55 @@  config IOMMU_DEBUGFS
 	  debug/iommu directory, and then populate a subdirectory with
 	  entries as required.
 
-config IOMMU_DEFAULT_PASSTHROUGH
-	bool "IOMMU passthrough by default"
-	depends on IOMMU_API
-	help
-	  Enable passthrough by default, removing the need to pass in
-	  iommu.passthrough=on or iommu=pt through command line. If this
-	  is enabled, you can still disable with iommu.passthrough=off
-	  or iommu=nopt depending on the architecture.
-
-	  If unsure, say N here.
-
 choice
-	prompt "IOMMU default DMA IOTLB invalidation mode"
-	depends on IOMMU_DMA
-
-	default IOMMU_DEFAULT_LAZY if (AMD_IOMMU || INTEL_IOMMU)
-	default IOMMU_DEFAULT_STRICT
+	prompt "IOMMU default domain type"
+	depends on IOMMU_API
+	default IOMMU_DEFAULT_DMA_LAZY if AMD_IOMMU || INTEL_IOMMU
+	default IOMMU_DEFAULT_DMA_STRICT
 	help
-	  This option allows an IOMMU DMA IOTLB invalidation mode to be
-	  chosen at build time, to override the default mode of each ARCH,
-	  removing the need to pass in kernel parameters through command line.
-	  It is still possible to provide common boot params to override this
-	  config.
+	  Choose the type of IOMMU domain used to manage DMA API usage by
+	  device drivers. The options here typically represent different
+	  levels of tradeoff between robustness/security and performance,
+	  depending on the IOMMU driver. Not all IOMMUs support all options.
+	  This choice can be overridden at boot via the command line, and for
+	  some devices also at runtime via sysfs.
 
 	  If unsure, keep the default.
 
-config IOMMU_DEFAULT_STRICT
-	bool "strict"
+config IOMMU_DEFAULT_DMA_STRICT
+	bool "Translated - Strict"
 	help
-	  For every IOMMU DMA unmap operation, the flush operation of IOTLB and
-	  the free operation of IOVA are guaranteed to be done in the unmap
-	  function.
+	  Trusted devices use translation to restrict their access to only
+	  DMA-mapped pages, with strict TLB invalidation on unmap. Equivalent
+	  to passing "iommu.passthrough=0 iommu.strict=1" on the command line.
 
-config IOMMU_DEFAULT_LAZY
-	bool "lazy"
+	  Untrusted devices always use this mode, with an additional layer of
+	  bounce-buffering such that they cannot gain access to any unrelated
+	  data within a mapped page.
+
+config IOMMU_DEFAULT_DMA_LAZY
+	bool "Translated - Lazy"
 	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.
+	  Trusted devices use translation to restrict their access to only
+	  DMA-mapped pages, but with "lazy" batched TLB invalidation. This
+	  mode allows higher performance with some IOMMUs due to reduced TLB
+	  flushing, but at the cost of reduced isolation since devices may be
+	  able to access memory for some time after it has been unmapped.
+	  Equivalent to passing "iommu.passthrough=0 iommu.strict=0" on the
+	  command line.
 
-	  The isolation provided in this mode is not as secure as STRICT mode,
-	  such that a vulnerable time window may be created between the DMA
-	  unmap and the mappings cached in the IOMMU IOTLB or device TLB
-	  finally being invalidated, where the device could still access the
-	  memory which has already been unmapped by the device driver.
-	  However this mode may provide better performance in high throughput
-	  scenarios, and is still considerably more secure than passthrough
-	  mode or no IOMMU.
+	  If this mode is not supported by the IOMMU driver, the effective
+	  runtime default will fall back to IOMMU_DEFAULT_DMA_STRICT.
+
+config IOMMU_DEFAULT_PASSTHROUGH
+	bool "Passthrough"
+	help
+	  Trusted devices are identity-mapped, giving them unrestricted access
+	  to memory with minimal performance overhead. Equivalent to passing
+	  "iommu.passthrough=1" (historically "iommu=pt") on the command line.
+
+	  If this mode is not supported by the IOMMU driver, the effective
+	  runtime default will fall back to IOMMU_DEFAULT_DMA_STRICT.
 
 endchoice
 
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 5a08e0806cbb..25c1adc1ec67 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -31,7 +31,7 @@  static struct kset *iommu_group_kset;
 static DEFINE_IDA(iommu_group_ida);
 
 static unsigned int iommu_def_domain_type __read_mostly;
-static bool iommu_dma_strict __read_mostly = IS_ENABLED(CONFIG_IOMMU_DEFAULT_STRICT);
+static bool iommu_dma_strict __read_mostly = IS_ENABLED(CONFIG_IOMMU_DEFAULT_DMA_STRICT);
 static u32 iommu_cmd_line __read_mostly;
 
 struct iommu_group {