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Date: Sat, 24 Jul 2021 13:29:34 +0800
From: Lu Baolu <baolu.lu@...ux.intel.com>
To: Robin Murphy <robin.murphy@....com>, joro@...tes.org,
will@...nel.org
Cc: baolu.lu@...ux.intel.com, iommu@...ts.linux-foundation.org,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
suravee.suthikulpanit@....com, john.garry@...wei.com,
dianders@...omium.org
Subject: Re: [PATCH 18/23] iommu: Express DMA strictness via the domain type
Hi Robin,
On 2021/7/22 2:20, Robin Murphy wrote:
> Eliminate the iommu_get_dma_strict() indirection and pipe the
> information through the domain type from the beginning. Besides
> the flow simplification this also has several nice side-effects:
>
> - Automatically implies strict mode for untrusted devices by
> virtue of their IOMMU_DOMAIN_DMA override.
> - Ensures that we only ends up using flush queues for drivers
> which are aware of them and can actually benefit.
Is this expressed by vendor iommu driver has ops->flush_iotlb_all?
> - Allows us to handle flush queue init failure by falling back
> to strict mode instead of leaving it to possibly blow up later.
>
> Signed-off-by: Robin Murphy <robin.murphy@....com>
> ---
> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 2 +-
> drivers/iommu/arm/arm-smmu/arm-smmu.c | 2 +-
> drivers/iommu/dma-iommu.c | 10 ++++++----
> drivers/iommu/iommu.c | 14 ++++----------
> include/linux/iommu.h | 1 -
> 5 files changed, 12 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> index fa41026d272e..260b560d0075 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> @@ -2175,7 +2175,7 @@ static int arm_smmu_domain_finalise(struct iommu_domain *domain,
> .iommu_dev = smmu->dev,
> };
>
> - if (!iommu_get_dma_strict(domain))
> + if (domain->type == IOMMU_DOMAIN_DMA_FQ)
> pgtbl_cfg.quirks |= IO_PGTABLE_QUIRK_NON_STRICT;
>
> pgtbl_ops = alloc_io_pgtable_ops(fmt, &pgtbl_cfg, smmu_domain);
> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c
> index dbc14c265b15..2c717f3be056 100644
> --- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
> @@ -765,7 +765,7 @@ static int arm_smmu_init_domain_context(struct iommu_domain *domain,
> .iommu_dev = smmu->dev,
> };
>
> - if (!iommu_get_dma_strict(domain))
> + if (domain->type == IOMMU_DOMAIN_DMA_FQ)
> pgtbl_cfg.quirks |= IO_PGTABLE_QUIRK_NON_STRICT;
>
> if (smmu->impl && smmu->impl->init_context) {
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index b1af1ff324c5..a114a7ad88ec 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -363,13 +363,15 @@ static int iommu_dma_init_domain(struct iommu_domain *domain, dma_addr_t base,
>
> init_iova_domain(iovad, 1UL << order, base_pfn);
>
> - if (!cookie->fq_domain && !dev_is_untrusted(dev) &&
> - domain->ops->flush_iotlb_all && !iommu_get_dma_strict(domain)) {
> + if (domain->type == IOMMU_DOMAIN_DMA_FQ && !cookie->fq_domain &&
> + domain->ops->flush_iotlb_all) {
> if (init_iova_flush_queue(iovad, iommu_dma_flush_iotlb_all,
> - iommu_dma_entry_dtor))
> + iommu_dma_entry_dtor)) {
> pr_warn("iova flush queue initialization failed\n");
> - else
> + domain->type = IOMMU_DOMAIN_DMA;
> + } else {
> cookie->fq_domain = domain;
> + }
> }
>
> return iova_reserve_iommu_regions(dev, domain);
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 8333c334891e..d7eaacae0944 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -135,6 +135,9 @@ static int __init iommu_subsys_init(void)
> }
> }
>
> + if (!iommu_default_passthrough() && !iommu_dma_strict)
> + iommu_def_domain_type = IOMMU_DOMAIN_DMA_FQ;
> +
> pr_info("Default domain type: %s %s\n",
> iommu_domain_type_str(iommu_def_domain_type),
> (iommu_cmd_line & IOMMU_CMD_LINE_DMA_API) ?
> @@ -352,15 +355,6 @@ void iommu_set_dma_strict(bool strict)
> iommu_dma_strict = strict;
> }
>
> -bool iommu_get_dma_strict(struct iommu_domain *domain)
> -{
> - /* only allow lazy flushing for DMA domains */
> - if (domain->type == IOMMU_DOMAIN_DMA)
> - return iommu_dma_strict;
> - return true;
> -}
> -EXPORT_SYMBOL_GPL(iommu_get_dma_strict);
> -
> static ssize_t iommu_group_attr_show(struct kobject *kobj,
> struct attribute *__attr, char *buf)
> {
> @@ -764,7 +758,7 @@ static int iommu_create_device_direct_mappings(struct iommu_group *group,
> unsigned long pg_size;
> int ret = 0;
>
> - if (!domain || domain->type != IOMMU_DOMAIN_DMA)
> + if (!domain || !(domain->type & __IOMMU_DOMAIN_DMA_API))
Nit: probably move above change to patch 14?
> return 0;
>
> BUG_ON(!domain->pgsize_bitmap);
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 56519110d43f..557c4c12e2cf 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -484,7 +484,6 @@ int iommu_set_pgtable_quirks(struct iommu_domain *domain,
> unsigned long quirks);
>
> void iommu_set_dma_strict(bool val);
> -bool iommu_get_dma_strict(struct iommu_domain *domain);
>
> extern int report_iommu_fault(struct iommu_domain *domain, struct device *dev,
> unsigned long iova, int flags);
>
Best regards,
baolu
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