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

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Date:	Thu, 21 May 2015 07:52:42 +0800
From:	Baoquan He <bhe@...hat.com>
To:	"Li, Zhen-Hua" <zhen-hual@...com>
Cc:	dwmw2@...radead.org, indou.takao@...fujitsu.com, joro@...tes.org,
	vgoyal@...hat.com, dyoung@...hat.com,
	iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, kexec@...ts.infradead.org,
	alex.williamson@...hat.com, ddutile@...hat.com,
	ishii.hironobu@...fujitsu.com, bhelgaas@...gle.com,
	doug.hatch@...com, jerry.hoemann@...com, tom.vaden@...com,
	li.zhang6@...com, lisa.mitchell@...com, billsumnerlinux@...il.com,
	rwright@...com
Subject: Re: [PATCH v11 08/10] iommu/vt-d: assign new page table for dma_map

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@...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
> 
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