linux-kernel - Re: [PATCH v3 24/25] iommu/dma: Factor out flush queue init

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Message-ID: <00baf83a-5eb3-4d72-309c-5adfd3242c07@arm.com>
Date:   Mon, 9 Aug 2021 20:59:35 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Rajat Jain <rajatja@...gle.com>
Cc:     joro@...tes.org, will@...nel.org, iommu@...ts.linux-foundation.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        suravee.suthikulpanit@....com, baolu.lu@...ux.intel.com,
        john.garry@...wei.com, dianders@...omium.org,
        chenxiang66@...ilicon.com
Subject: Re: [PATCH v3 24/25] iommu/dma: Factor out flush queue init

On 2021-08-09 20:05, Rajat Jain wrote:
> On Wed, Aug 4, 2021 at 10:16 AM Robin Murphy <robin.murphy@....com> wrote:
>>
>> Factor out flush queue setup from the initial domain init so that we
>> can potentially trigger it from sysfs later on in a domain's lifetime.
>>
>> Reviewed-by: Lu Baolu <baolu.lu@...ux.intel.com>
>> Reviewed-by: John Garry <john.garry@...wei.com>
>> Signed-off-by: Robin Murphy <robin.murphy@....com>
>> ---
>>   drivers/iommu/dma-iommu.c | 30 ++++++++++++++++++++----------
>>   include/linux/dma-iommu.h |  9 ++++++---
>>   2 files changed, 26 insertions(+), 13 deletions(-)
>>
>> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
>> index 2e19505dddf9..f51b8dc99ac6 100644
>> --- a/drivers/iommu/dma-iommu.c
>> +++ b/drivers/iommu/dma-iommu.c
>> @@ -310,6 +310,25 @@ static bool dev_is_untrusted(struct device *dev)
>>          return dev_is_pci(dev) && to_pci_dev(dev)->untrusted;
>>   }
>>
>> +int iommu_dma_init_fq(struct iommu_domain *domain)
>> +{
>> +       struct iommu_dma_cookie *cookie = domain->iova_cookie;
>> +
>> +       if (domain->type != IOMMU_DOMAIN_DMA_FQ)
>> +               return -EINVAL;
>> +       if (cookie->fq_domain)
>> +               return 0;
>> +
>> +       if (init_iova_flush_queue(&cookie->iovad, iommu_dma_flush_iotlb_all,
>> +                                 iommu_dma_entry_dtor)) {
>> +               pr_warn("iova flush queue initialization failed\n");
>> +               domain->type = IOMMU_DOMAIN_DMA;
>> +               return -ENODEV;
>> +       }
>> +       cookie->fq_domain = domain;
>> +       return 0;
>> +}
>> +
>>   /**
>>    * iommu_dma_init_domain - Initialise a DMA mapping domain
>>    * @domain: IOMMU domain previously prepared by iommu_get_dma_cookie()
>> @@ -362,16 +381,7 @@ static int iommu_dma_init_domain(struct iommu_domain *domain, dma_addr_t base,
>>          }
>>
>>          init_iova_domain(iovad, 1UL << order, base_pfn);
>> -
>> -       if (domain->type == IOMMU_DOMAIN_DMA_FQ && !cookie->fq_domain) {
>> -               if (init_iova_flush_queue(iovad, iommu_dma_flush_iotlb_all,
>> -                                         iommu_dma_entry_dtor)) {
>> -                       pr_warn("iova flush queue initialization failed\n");
>> -                       domain->type = IOMMU_DOMAIN_DMA;
>> -               } else {
>> -                       cookie->fq_domain = domain;
>> -               }
>> -       }
>> +       iommu_dma_init_fq(domain);
>>
>>          return iova_reserve_iommu_regions(dev, domain);
>>   }
>> diff --git a/include/linux/dma-iommu.h b/include/linux/dma-iommu.h
>> index 758ca4694257..81ab647f1618 100644
>> --- a/include/linux/dma-iommu.h
>> +++ b/include/linux/dma-iommu.h
>> @@ -20,6 +20,7 @@ void iommu_put_dma_cookie(struct iommu_domain *domain);
>>
>>   /* Setup call for arch DMA mapping code */
>>   void iommu_setup_dma_ops(struct device *dev, u64 dma_base, u64 dma_limit);
>> +int iommu_dma_init_fq(struct iommu_domain *domain);
>>
>>   /* The DMA API isn't _quite_ the whole story, though... */
>>   /*
>> @@ -37,9 +38,6 @@ void iommu_dma_compose_msi_msg(struct msi_desc *desc,
>>
>>   void iommu_dma_get_resv_regions(struct device *dev, struct list_head *list);
>>
>> -void iommu_dma_free_cpu_cached_iovas(unsigned int cpu,
>> -               struct iommu_domain *domain);
>> -
> 
> This looks like an unrelated code cleanup. Should this be a separate patch?

Ha, busted! Much of this was done in the "stream of consciousness" style 
where I made a big sprawling mess then split it up into patches and 
branches afterwards. TBH it was already feeling pretty tenuous having a 
separate patch just to move this one function, and it only gets more so 
with the simplification Will pointed out earlier. I think I'll squash 
iommu_dma_init_fq() into the next patch then do a thorough header sweep, 
since I've now spotted some things in iova.h which could probably go as 
well.

Thanks for the poke!

Robin.

> 
> Thanks,
> 
> Rajat
> 
> 
>>   extern bool iommu_dma_forcedac;
>>
>>   #else /* CONFIG_IOMMU_DMA */
>> @@ -54,6 +52,11 @@ static inline void iommu_setup_dma_ops(struct device *dev, u64 dma_base,
>>   {
>>   }
>>
>> +static inline int iommu_dma_init_fq(struct iommu_domain *domain)
>> +{
>> +       return -EINVAL;
>> +}
>> +
>>   static inline int iommu_get_dma_cookie(struct iommu_domain *domain)
>>   {
>>          return -ENODEV;
>> --
>> 2.25.1
>>