linux-kernel - Re: [PATCH v5 7/7] iommu/dma: Move PCI window region reservation back into dma specific path.

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Date:   Thu, 22 Mar 2018 17:22:27 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Alex Williamson <alex.williamson@...hat.com>,
        Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>
Cc:     eric.auger@...hat.com, pmorel@...ux.vnet.ibm.com,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        iommu@...ts.linux-foundation.org, linuxarm@...wei.com,
        john.garry@...wei.com, xuwei5@...ilicon.com,
        Joerg Roedel <joro@...tes.org>
Subject: Re: [PATCH v5 7/7] iommu/dma: Move PCI window region reservation back
 into dma specific path.

On 22/03/18 16:21, Alex Williamson wrote:
> On Thu, 15 Mar 2018 16:35:09 +0000
> Shameer Kolothum <shameerali.kolothum.thodi@...wei.com> wrote:
> 
>> This pretty much reverts commit 273df9635385 ("iommu/dma: Make PCI
>> window reservation generic")  by moving the PCI window region
>> reservation back into the dma specific path so that these regions
>> doesn't get exposed via the IOMMU API interface. With this change,
>> the vfio interface will report only iommu specific reserved regions
>> to the user space.
>>
>> Cc: Robin Murphy <robin.murphy@....com>
>> Cc: Joerg Roedel <joro@...tes.org>
>> Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>
>> ---
> 
> As currently ordered, we expose the iova list to the user in 5/7 with
> the PCI window reservations still intact.  Isn't that a bisection
> problem?  This patch should come before the iova list is expose to the
> user.  This is otherwise independent, so I can pop it up in the stack on
> commit, but I'd need an ack from Joerg and Robin to take it via my
> tree.  Thanks,

If it counts, the changes look right, so:

Acked-by: Robin Murphy <robin.murphy@....com>

but it does look like there's a hard dependency on Joerg's core branch 
where Shameer's ITS workaround patches are currently queued. Otherwise, 
though, I don't think there's anything else due to be touching iommu-dma 
just yet.

Robin.

> 
> Alex
> 
>>   drivers/iommu/dma-iommu.c | 54 ++++++++++++++++++++++-------------------------
>>   1 file changed, 25 insertions(+), 29 deletions(-)
>>
>> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
>> index f05f3cf..ddcbbdb 100644
>> --- a/drivers/iommu/dma-iommu.c
>> +++ b/drivers/iommu/dma-iommu.c
>> @@ -167,40 +167,16 @@ EXPORT_SYMBOL(iommu_put_dma_cookie);
>>    * @list: Reserved region list from iommu_get_resv_regions()
>>    *
>>    * IOMMU drivers can use this to implement their .get_resv_regions callback
>> - * for general non-IOMMU-specific reservations. Currently, this covers host
>> - * bridge windows for PCI devices and GICv3 ITS region reservation on ACPI
>> - * based ARM platforms that may require HW MSI reservation.
>> + * for general non-IOMMU-specific reservations. Currently, this covers GICv3
>> + * ITS region reservation on ACPI based ARM platforms that may require HW MSI
>> + * reservation.
>>    */
>>   void iommu_dma_get_resv_regions(struct device *dev, struct list_head *list)
>>   {
>> -	struct pci_host_bridge *bridge;
>> -	struct resource_entry *window;
>> -
>> -	if (!is_of_node(dev->iommu_fwspec->iommu_fwnode) &&
>> -		iort_iommu_msi_get_resv_regions(dev, list) < 0)
>> -		return;
>> -
>> -	if (!dev_is_pci(dev))
>> -		return;
>> -
>> -	bridge = pci_find_host_bridge(to_pci_dev(dev)->bus);
>> -	resource_list_for_each_entry(window, &bridge->windows) {
>> -		struct iommu_resv_region *region;
>> -		phys_addr_t start;
>> -		size_t length;
>> -
>> -		if (resource_type(window->res) != IORESOURCE_MEM)
>> -			continue;
>>   
>> -		start = window->res->start - window->offset;
>> -		length = window->res->end - window->res->start + 1;
>> -		region = iommu_alloc_resv_region(start, length, 0,
>> -				IOMMU_RESV_RESERVED);
>> -		if (!region)
>> -			return;
>> +	if (!is_of_node(dev->iommu_fwspec->iommu_fwnode))
>> +		iort_iommu_msi_get_resv_regions(dev, list);
>>   
>> -		list_add_tail(&region->list, list);
>> -	}
>>   }
>>   EXPORT_SYMBOL(iommu_dma_get_resv_regions);
>>   
>> @@ -229,6 +205,23 @@ static int cookie_init_hw_msi_region(struct iommu_dma_cookie *cookie,
>>   	return 0;
>>   }
>>   
>> +static void iova_reserve_pci_windows(struct pci_dev *dev,
>> +		struct iova_domain *iovad)
>> +{
>> +	struct pci_host_bridge *bridge = pci_find_host_bridge(dev->bus);
>> +	struct resource_entry *window;
>> +	unsigned long lo, hi;
>> +
>> +	resource_list_for_each_entry(window, &bridge->windows) {
>> +		if (resource_type(window->res) != IORESOURCE_MEM)
>> +			continue;
>> +
>> +		lo = iova_pfn(iovad, window->res->start - window->offset);
>> +		hi = iova_pfn(iovad, window->res->end - window->offset);
>> +		reserve_iova(iovad, lo, hi);
>> +	}
>> +}
>> +
>>   static int iova_reserve_iommu_regions(struct device *dev,
>>   		struct iommu_domain *domain)
>>   {
>> @@ -238,6 +231,9 @@ static int iova_reserve_iommu_regions(struct device *dev,
>>   	LIST_HEAD(resv_regions);
>>   	int ret = 0;
>>   
>> +	if (dev_is_pci(dev))
>> +		iova_reserve_pci_windows(to_pci_dev(dev), iovad);
>> +
>>   	iommu_get_resv_regions(dev, &resv_regions);
>>   	list_for_each_entry(region, &resv_regions, list) {
>>   		unsigned long lo, hi;
>