Re: [PATCH v2 20/24] iommu: Merge strictness and domain type configs
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
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Re: [PATCH v2 20/24] iommu: Merge strictness and domain type configs
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 > Signed-off-by: Robin Murphy kernel-parameters.txt still refers to the old config options Otherwise Reviewed-by: Jean-Philippe Brucker > --- > 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.
Re: [PATCH v2 20/24] iommu: Merge strictness and domain type configs
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 Signed-off-by: Robin Murphy --- 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 +
[PATCH v2 20/24] iommu: Merge strictness and domain type configs
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 Signed-off-by: Robin Murphy --- 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
