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Message-ID: <77057c4b-479b-c5b8-4666-f16e294552d1@arm.com>
Date: Mon, 26 Jul 2021 09:27:01 +0100
From: Robin Murphy <robin.murphy@....com>
To: Lu Baolu <baolu.lu@...ux.intel.com>, joro@...tes.org,
will@...nel.org
Cc: 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
On 2021-07-24 06:29, Lu Baolu wrote:
> 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?
No, it's literally whether ->domain_alloc accepts the DMA_DOMAIN_FQ type
or not.
>> - 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?
Indeed I'm not sure why this one ended up here, good catch!
Thanks,
Robin.
>> 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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