Re: [PATCH v11 08/10] iommu/vt-d: assign new page table for dma_map

["Li, ZhenHua" <zhen-hual@hp.com>]

Hi Baoquan,

In the early version of this patchset, old page tables are used by new
kernel.  But as discussed, we need to make kernel use new pages when
there is a new dma request , so we need to unmap the pages which were
mapped in old kernel, and this is what this patch does.

Thanks
Zhenhua

On 05/21/2015 07:52 AM, Baoquan He wrote:
> On 05/11/15 at 05:52pm, Li, Zhen-Hua wrote:
>> When a device driver issues the first dma_map command for a device, we
>> assign a new and empty page-table, thus removing all mappings from the
>> old kernel for the device.
>
> Hi Zhenhua,
>
>  From your patch I got it will remove all mappings, assign a new
> page-table. But I didn't got why you stress an empty page-table. Did I
> miss anything?
>
> Thanks
> Baoquan
>
>>
>> Signed-off-by: Li, Zhen-Hua <zhen-hual@hp.com>
>> ---
>>   drivers/iommu/intel-iommu.c | 58 ++++++++++++++++++++++++++++++++++++++-------
>>   1 file changed, 50 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
>> index 91545bf..3cc1027 100644
>> --- a/drivers/iommu/intel-iommu.c
>> +++ b/drivers/iommu/intel-iommu.c
>> @@ -396,6 +396,9 @@ static int copy_root_entry_table(struct intel_iommu *iommu);
>>
>>   static int intel_iommu_load_translation_tables(struct intel_iommu *iommu);
>>
>> +static void unmap_device_dma(struct dmar_domain *domain,
>> +				struct device *dev,
>> +				struct intel_iommu *iommu);
>>   static void iommu_check_pre_te_status(struct intel_iommu *iommu);
>>   static u8 g_translation_pre_enabled;
>>
>> @@ -3115,6 +3118,7 @@ static struct iova *intel_alloc_iova(struct device *dev,
>>   static struct dmar_domain *__get_valid_domain_for_dev(struct device *dev)
>>   {
>>   	struct dmar_domain *domain;
>> +	struct intel_iommu *iommu;
>>   	int ret;
>>
>>   	domain = get_domain_for_dev(dev, DEFAULT_DOMAIN_ADDRESS_WIDTH);
>> @@ -3124,14 +3128,30 @@ static struct dmar_domain *__get_valid_domain_for_dev(struct device *dev)
>>   		return NULL;
>>   	}
>>
>> -	/* make sure context mapping is ok */
>> -	if (unlikely(!domain_context_mapped(dev))) {
>> -		ret = domain_context_mapping(domain, dev, CONTEXT_TT_MULTI_LEVEL);
>> -		if (ret) {
>> -			printk(KERN_ERR "Domain context map for %s failed",
>> -			       dev_name(dev));
>> -			return NULL;
>> -		}
>> +	/* if in kdump kernel, we need to unmap the mapped dma pages,
>> +	 * detach this device first.
>> +	 */
>> +	if (likely(domain_context_mapped(dev))) {
>> +		iommu = domain_get_iommu(domain);
>> +		if (iommu->pre_enabled_trans) {
>> +			unmap_device_dma(domain, dev, iommu);
>> +
>> +			domain = get_domain_for_dev(dev,
>> +				DEFAULT_DOMAIN_ADDRESS_WIDTH);
>> +			if (!domain) {
>> +				pr_err("Allocating domain for %s failed",
>> +				       dev_name(dev));
>> +				return NULL;
>> +			}
>> +		} else
>> +			return domain;
>> +	}
>> +
>> +	ret = domain_context_mapping(domain, dev, CONTEXT_TT_MULTI_LEVEL);
>> +	if (ret) {
>> +		pr_err("Domain context map for %s failed",
>> +		       dev_name(dev));
>> +		return NULL;
>>   	}
>>
>>   	return domain;
>> @@ -5168,6 +5188,28 @@ static int intel_iommu_load_translation_tables(struct intel_iommu *iommu)
>>   	return ret;
>>   }
>>
>> +static void unmap_device_dma(struct dmar_domain *domain,
>> +				struct device *dev,
>> +				struct intel_iommu *iommu)
>> +{
>> +	struct context_entry *ce;
>> +	struct iova *iova;
>> +	phys_addr_t phys_addr;
>> +	dma_addr_t dev_addr;
>> +	struct pci_dev *pdev;
>> +
>> +	pdev = to_pci_dev(dev);
>> +	ce = iommu_context_addr(iommu, pdev->bus->number, pdev->devfn, 1);
>> +	phys_addr = context_address_root(ce) << VTD_PAGE_SHIFT;
>> +	dev_addr = phys_to_dma(dev, phys_addr);
>> +
>> +	iova = find_iova(&domain->iovad, IOVA_PFN(dev_addr));
>> +	if (iova)
>> +		intel_unmap(dev, dev_addr);
>> +
>> +	domain_remove_one_dev_info(domain, dev);
>> +}
>> +
>>   static void iommu_check_pre_te_status(struct intel_iommu *iommu)
>>   {
>>   	u32 sts;
>> --
>> 2.0.0-rc0
>>