linux-kernel - Re: [RFC PATCH 3/4] iommu/vt-d: Map/unmap domain with mmmap/mmunmap

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Date:   Wed, 25 Sep 2019 15:06:43 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     "Tian, Kevin" <kevin.tian@...el.com>,
        Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Alex Williamson <alex.williamson@...hat.com>
Cc:     baolu.lu@...ux.intel.com, "Raj, Ashok" <ashok.raj@...el.com>,
        "Kumar, Sanjay K" <sanjay.k.kumar@...el.com>,
        "jacob.jun.pan@...ux.intel.com" <jacob.jun.pan@...ux.intel.com>,
        "Liu, Yi L" <yi.l.liu@...el.com>, "Sun, Yi Y" <yi.y.sun@...el.com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Yi Sun <yi.y.sun@...ux.intel.com>
Subject: Re: [RFC PATCH 3/4] iommu/vt-d: Map/unmap domain with mmmap/mmunmap

Hi,

On 9/25/19 1:00 PM, Tian, Kevin wrote:
>> From: Lu Baolu [mailto:baolu.lu@...ux.intel.com]
>> Sent: Monday, September 23, 2019 8:25 PM
>>
>> If a dmar domain has DOMAIN_FLAG_FIRST_LEVEL_TRANS bit set
>> in its flags, IOMMU will use the first level page table for
>> translation. Hence, we need to map or unmap addresses in the
>> first level page table.
>>
>> Cc: Ashok Raj <ashok.raj@...el.com>
>> Cc: Jacob Pan <jacob.jun.pan@...ux.intel.com>
>> Cc: Kevin Tian <kevin.tian@...el.com>
>> Cc: Liu Yi L <yi.l.liu@...el.com>
>> Cc: Yi Sun <yi.y.sun@...ux.intel.com>
>> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
>> ---
>>   drivers/iommu/intel-iommu.c | 94 ++++++++++++++++++++++++++++++++-
>> ----
>>   1 file changed, 82 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
>> index 9cfe8098d993..103480016010 100644
>> --- a/drivers/iommu/intel-iommu.c
>> +++ b/drivers/iommu/intel-iommu.c
>> @@ -168,6 +168,11 @@ static inline unsigned long virt_to_dma_pfn(void
>> *p)
>>   	return page_to_dma_pfn(virt_to_page(p));
>>   }
>>
>> +static inline unsigned long dma_pfn_to_addr(unsigned long pfn)
>> +{
>> +	return pfn << VTD_PAGE_SHIFT;
>> +}
>> +
>>   /* global iommu list, set NULL for ignored DMAR units */
>>   static struct intel_iommu **g_iommus;
>>
>> @@ -307,6 +312,9 @@ static int hw_pass_through = 1;
>>    */
>>   #define DOMAIN_FLAG_LOSE_CHILDREN		BIT(1)
>>
>> +/* Domain uses first level translation for DMA remapping. */
>> +#define DOMAIN_FLAG_FIRST_LEVEL_TRANS		BIT(2)
>> +
>>   #define for_each_domain_iommu(idx, domain)			\
>>   	for (idx = 0; idx < g_num_of_iommus; idx++)		\
>>   		if (domain->iommu_refcnt[idx])
>> @@ -552,6 +560,11 @@ static inline int domain_type_is_si(struct
>> dmar_domain *domain)
>>   	return domain->flags & DOMAIN_FLAG_STATIC_IDENTITY;
>>   }
>>
>> +static inline int domain_type_is_flt(struct dmar_domain *domain)
>> +{
>> +	return domain->flags & DOMAIN_FLAG_FIRST_LEVEL_TRANS;
>> +}
>> +
>>   static inline int domain_pfn_supported(struct dmar_domain *domain,
>>   				       unsigned long pfn)
>>   {
>> @@ -1147,8 +1160,15 @@ static struct page *domain_unmap(struct
>> dmar_domain *domain,
>>   	BUG_ON(start_pfn > last_pfn);
>>
>>   	/* we don't need lock here; nobody else touches the iova range */
>> -	freelist = dma_pte_clear_level(domain, agaw_to_level(domain-
>>> agaw),
>> -				       domain->pgd, 0, start_pfn, last_pfn,
>> NULL);
>> +	if (domain_type_is_flt(domain))
>> +		freelist = intel_mmunmap_range(domain,
>> +					       dma_pfn_to_addr(start_pfn),
>> +					       dma_pfn_to_addr(last_pfn + 1));
>> +	else
>> +		freelist = dma_pte_clear_level(domain,
>> +					       agaw_to_level(domain->agaw),
>> +					       domain->pgd, 0, start_pfn,
>> +					       last_pfn, NULL);
> 
> what about providing an unified interface at the caller side, then having
> the level differentiated within the interface?

Good point! I ever thought about adding some ops in struct dmar_domain,
something like:

diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
index ed11ef594378..1dd184f76bfb 100644
--- a/include/linux/intel-iommu.h
+++ b/include/linux/intel-iommu.h
@@ -489,7 +489,14 @@ struct dmar_domain {
         struct list_head auxd;          /* link to device's auxiliary 
list */
         struct iova_domain iovad;       /* iova's that belong to this 
domain */

+       /* per domain page table and manipulation ops */
         struct dma_pte  *pgd;           /* virtual address */
+       int (*map)(struct dmar_domain *domain,
+                  unsigned long addr, unsigned long end,
+                  phys_addr_t phys_addr, int dma_prot);
+       struct page *(*unmap)(struct dmar_domain *domain,
+                             unsigned long addr, unsigned long end);
+
         int             gaw;            /* max guest address width */

         /* adjusted guest address width, 0 is level 2 30-bit */

So that this code could be simply like this:

	freelist = domain->unmap(...);

Best regards,
Baolu