linux-kernel - Re: [PATCH v5 2/7] iommu/vt-d: Duplicate iommu_resv

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Message-ID: <e22ccc46-7c37-c8d2-784b-3d4168512772@linux.intel.com>
Date:   Wed, 29 May 2019 10:04:19 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Eric Auger <eric.auger@...hat.com>, eric.auger.pro@...il.com,
        joro@...tes.org, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, dwmw2@...radead.org,
        robin.murphy@....com
Cc:     baolu.lu@...ux.intel.com, alex.williamson@...hat.com,
        shameerali.kolothum.thodi@...wei.com, jean-philippe.brucker@....com
Subject: Re: [PATCH v5 2/7] iommu/vt-d: Duplicate iommu_resv_region objects
 per device list

Hi Eric,

On 5/28/19 7:50 PM, Eric Auger wrote:
> intel_iommu_get_resv_regions() aims to return the list of
> reserved regions accessible by a given @device. However several
> devices can access the same reserved memory region and when
> building the list it is not safe to use a single iommu_resv_region
> object, whose container is the RMRR. This iommu_resv_region must
> be duplicated per device reserved region list.
> 
> Let's remove the struct iommu_resv_region from the RMRR unit
> and allocate the iommu_resv_region directly in
> intel_iommu_get_resv_regions(). We hold the dmar_global_lock instead
> of the rcu-lock to allow sleeping.
> 
> Fixes: 0659b8dc45a6 ("iommu/vt-d: Implement reserved region get/put callbacks")
> Signed-off-by: Eric Auger <eric.auger@...hat.com>
> 
> ---
> 
> v4 -> v5
> - replace rcu-lock by the dmar_global_lock
> ---
>   drivers/iommu/intel-iommu.c | 34 +++++++++++++++++-----------------
>   1 file changed, 17 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index a209199f3af6..5ec8b5bd308f 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -322,7 +322,6 @@ struct dmar_rmrr_unit {
>   	u64	end_address;		/* reserved end address */
>   	struct dmar_dev_scope *devices;	/* target devices */
>   	int	devices_cnt;		/* target device count */
> -	struct iommu_resv_region *resv; /* reserved region handle */
>   };
>   
>   struct dmar_atsr_unit {
> @@ -4205,7 +4204,6 @@ static inline void init_iommu_pm_ops(void) {}
>   int __init dmar_parse_one_rmrr(struct acpi_dmar_header *header, void *arg)
>   {
>   	struct acpi_dmar_reserved_memory *rmrr;
> -	int prot = DMA_PTE_READ|DMA_PTE_WRITE;
>   	struct dmar_rmrr_unit *rmrru;
>   	size_t length;
>   
> @@ -4219,22 +4217,16 @@ int __init dmar_parse_one_rmrr(struct acpi_dmar_header *header, void *arg)
>   	rmrru->end_address = rmrr->end_address;
>   
>   	length = rmrr->end_address - rmrr->base_address + 1;
> -	rmrru->resv = iommu_alloc_resv_region(rmrr->base_address, length, prot,
> -					      IOMMU_RESV_DIRECT);
> -	if (!rmrru->resv)
> -		goto free_rmrru;
>   
>   	rmrru->devices = dmar_alloc_dev_scope((void *)(rmrr + 1),
>   				((void *)rmrr) + rmrr->header.length,
>   				&rmrru->devices_cnt);
>   	if (rmrru->devices_cnt && rmrru->devices == NULL)
> -		goto free_all;
> +		goto free_rmrru;
>   
>   	list_add(&rmrru->list, &dmar_rmrr_units);
>   
>   	return 0;
> -free_all:
> -	kfree(rmrru->resv);
>   free_rmrru:
>   	kfree(rmrru);
>   out:
> @@ -4452,7 +4444,6 @@ static void intel_iommu_free_dmars(void)
>   	list_for_each_entry_safe(rmrru, rmrr_n, &dmar_rmrr_units, list) {
>   		list_del(&rmrru->list);
>   		dmar_free_dev_scope(&rmrru->devices, &rmrru->devices_cnt);
> -		kfree(rmrru->resv);
>   		kfree(rmrru);
>   	}
>   
> @@ -5470,22 +5461,33 @@ static void intel_iommu_remove_device(struct device *dev)
>   static void intel_iommu_get_resv_regions(struct device *device,
>   					 struct list_head *head)
>   {
> +	int prot = DMA_PTE_READ|DMA_PTE_WRITE;

I know this is moved from above. How about adding spaces around the '|'?

>   	struct iommu_resv_region *reg;
>   	struct dmar_rmrr_unit *rmrr;
>   	struct device *i_dev;
>   	int i;
>   
> -	rcu_read_lock();
> +	down_write(&dmar_global_lock);

Just out of curiosity, why not down_read()? We don't change the rmrr
list here, right?

>   	for_each_rmrr_units(rmrr) {
>   		for_each_active_dev_scope(rmrr->devices, rmrr->devices_cnt,
>   					  i, i_dev) {
> +			struct iommu_resv_region *resv;
> +			size_t length;
> +
>   			if (i_dev != device)
>   				continue;
>   
> -			list_add_tail(&rmrr->resv->list, head);
> +			length = rmrr->end_address - rmrr->base_address + 1;
> +			resv = iommu_alloc_resv_region(rmrr->base_address,
> +						       length, prot,
> +						       IOMMU_RESV_DIRECT);
> +			if (!resv)
> +				break;
> +
> +			list_add_tail(&resv->list, head);
>   		}
>   	}
> -	rcu_read_unlock();
> +	up_write(&dmar_global_lock);
>   
>   	reg = iommu_alloc_resv_region(IOAPIC_RANGE_START,
>   				      IOAPIC_RANGE_END - IOAPIC_RANGE_START + 1,
> @@ -5500,10 +5502,8 @@ static void intel_iommu_put_resv_regions(struct device *dev,
>   {
>   	struct iommu_resv_region *entry, *next;
>   
> -	list_for_each_entry_safe(entry, next, head, list) {
> -		if (entry->type == IOMMU_RESV_MSI)
> -			kfree(entry);
> -	}
> +	list_for_each_entry_safe(entry, next, head, list)
> +		kfree(entry);
>   }
>   
>   int intel_iommu_enable_pasid(struct intel_iommu *iommu, struct device *dev)
> 

Other looks good to me.

Reviewed-by: Lu Baolu <baolu.lu@...ux.intel.com>

Best regards,
Baolu