On Thu, Sep 20, 2018 at 05:10:23PM +0100, Robin Murphy wrote:
> From: Zhen Lei <[email protected]>
>
> Add a generic command line option to enable lazy unmapping via IOVA
> flush queues, which will initally be suuported by iommu-dma. This echoes
> the semantics of "intel_iommu=strict" (albeit with the opposite default
> value), but in the driver-agnostic fashion of "iommu.passthrough".
>
> Signed-off-by: Zhen Lei <[email protected]>
> [rm: move handling out of SMMUv3 driver, clean up documentation]
> Signed-off-by: Robin Murphy <[email protected]>
> ---
>
> v8:
> - Rename "non-strict" to "strict" to better match existing options
> - Rewrite doc text/commit message
> - Downgrade boot-time message from warn/taint to info
>
> .../admin-guide/kernel-parameters.txt | 12 ++++++++++
> drivers/iommu/iommu.c | 23 +++++++++++++++++++
> 2 files changed, 35 insertions(+)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt
> b/Documentation/admin-guide/kernel-parameters.txt
> index 9871e649ffef..92ae12aeabf4 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -1749,6 +1749,18 @@
> nobypass [PPC/POWERNV]
> Disable IOMMU bypass, using IOMMU for PCI devices.
>
> + iommu.strict= [ARM64] Configure TLB invalidation behaviour
> + Format: { "0" | "1" }
> + 0 - Lazy mode.
> + Request that DMA unmap operations use deferred
> + invalidation of hardware TLBs, for increased
> + throughput at the cost of reduced device isolation.
> + Will fall back to strict mode if not supported by
> + the relevant IOMMU driver.
> + 1 - Strict mode (default).
> + DMA unmap operations invalidate IOMMU hardware TLBs
> + synchronously.
> +
> iommu.passthrough=
> [ARM64] Configure DMA to bypass the IOMMU by default.
> Format: { "0" | "1" }
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 8c15c5980299..02b6603f0616 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -41,6 +41,7 @@ static unsigned int iommu_def_domain_type =
> IOMMU_DOMAIN_IDENTITY;
> #else
> static unsigned int iommu_def_domain_type = IOMMU_DOMAIN_DMA;
> #endif
> +static bool iommu_dma_strict __read_mostly = true;
>
> struct iommu_callback_data {
> const struct iommu_ops *ops;
> @@ -131,6 +132,21 @@ static int __init iommu_set_def_domain_type(char *str)
> }
> early_param("iommu.passthrough", iommu_set_def_domain_type);
>
> +static int __init iommu_dma_setup(char *str)
> +{
> + int ret;
> +
> + ret = kstrtobool(str, &iommu_dma_strict);
> + if (ret)
> + return ret;
> +
> + if (!iommu_dma_strict)
> + pr_info("Enabling deferred TLB invalidation for DMA; protection
> against malicious/malfunctioning devices may be reduced.\n");
Printing here isn't quite right, because if somebody boots with something
like:
"iommu.strict=1 iommu.strict=0 iommu.strict=0 iommu.strict=1"
then we'll print the wrong thing twice :)
I think we either need to drop the print, or move it to a the DMA domain
initialisation.
Will
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