Re: [PATCH v11 07/10] iommu/vt-d: enable kdump support in iommu module

[Dave Young]

On 05/11/15 at 05:52pm, Li, Zhen-Hua wrote:
> Modify the operation of the following functions when called during crash dump:
>     iommu_context_addr
>     free_context_table
>     get_domain_for_dev
>     init_dmars
>     intel_iommu_init
> 
> Bill Sumner:
>     Original version.
> 
> Zhenhua:
>     The name of new calling functions.
>     Do not disable and re-enable TE in kdump kernel.
>     Use the did and gaw from old context entry;
> 
> Signed-off-by: Bill Sumner <billsumnerlinux@xxxxxxxxx>
> Signed-off-by: Li, Zhen-Hua <zhen-hual@xxxxxx>
> ---
>  drivers/iommu/intel-iommu.c | 95 +++++++++++++++++++++++++++++++++++++++------
>  1 file changed, 83 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index 28c3c64..91545bf 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -397,6 +397,7 @@ static int copy_root_entry_table(struct intel_iommu *iommu);
>  static int intel_iommu_load_translation_tables(struct intel_iommu *iommu);
>  
>  static void iommu_check_pre_te_status(struct intel_iommu *iommu);
> +static u8 g_translation_pre_enabled;
>  
>  /*
>   * This domain is a statically identity mapping domain.
> @@ -794,6 +795,9 @@ static inline struct context_entry *iommu_context_addr(struct intel_iommu *iommu
>  		phy_addr = virt_to_phys((void *)context);
>  		*entry = phy_addr | 1;
>  		__iommu_flush_cache(iommu, entry, sizeof(*entry));
> +
> +		if (iommu->pre_enabled_trans)
> +			__iommu_update_old_root_entry(iommu, bus);
>  	}
>  	return &context[devfn];
>  }
> @@ -887,13 +891,15 @@ static void clear_context_table(struct intel_iommu *iommu, u8 bus, u8 devfn)
>  
>  static void free_context_table(struct intel_iommu *iommu)
>  {
> +	struct root_entry *root = NULL;
>  	int i;
>  	unsigned long flags;
>  	struct context_entry *context;
>  
>  	spin_lock_irqsave(&iommu->lock, flags);
>  	if (!iommu->root_entry) {
> -		goto out;
> +		spin_unlock_irqrestore(&iommu->lock, flags);
> +		return;
>  	}
>  	for (i = 0; i < ROOT_ENTRY_NR; i++) {
>  		context = iommu_context_addr(iommu, i, 0, 0);
> @@ -908,10 +914,23 @@ static void free_context_table(struct intel_iommu *iommu)
>  			free_pgtable_page(context);
>  
>  	}
> +
> +	if (iommu->pre_enabled_trans) {
> +		iommu->root_entry_old_phys = 0;
> +		root = iommu->root_entry_old_virt;
> +		iommu->root_entry_old_virt = NULL;
> +	}
> +
>  	free_pgtable_page(iommu->root_entry);
>  	iommu->root_entry = NULL;
> -out:
> +
>  	spin_unlock_irqrestore(&iommu->lock, flags);
> +
> +	/* We put this out of spin_unlock is because iounmap() may
> +	 * cause error if surrounded by spin_lock and unlock;
> +	 */
> +	if (iommu->pre_enabled_trans)
> +		iounmap(root);
>  }
>  
>  static struct dma_pte *pfn_to_dma_pte(struct dmar_domain *domain,
> @@ -2333,6 +2352,7 @@ static struct dmar_domain *get_domain_for_dev(struct device *dev, int gaw)
>  	unsigned long flags;
>  	u8 bus, devfn;
>  	int did = -1;   /* Default to "no domain_id supplied" */
> +	struct context_entry *ce = NULL;
>  
>  	domain = find_domain(dev);
>  	if (domain)
> @@ -2366,6 +2386,20 @@ static struct dmar_domain *get_domain_for_dev(struct device *dev, int gaw)
>  	domain = alloc_domain(0);
>  	if (!domain)
>  		return NULL;
> +
> +	if (iommu->pre_enabled_trans) {
> +		/*
> +		 * if this device had a did in the old kernel
> +		 * use its values instead of generating new ones
> +		 */
> +		ce = device_to_existing_context_entry(iommu, bus, devfn);
> +
> +		if (ce) {
> +			did = context_domain_id(ce);
> +			gaw = agaw_to_width(context_address_width(ce));
> +		}
> +	}
> +
>  	domain->id = iommu_attach_domain_with_id(domain, iommu, did);
>  	if (domain->id < 0) {
>  		free_domain_mem(domain);
> @@ -2897,6 +2931,7 @@ static int __init init_dmars(void)
>  		goto free_g_iommus;
>  	}
>  
> +	g_translation_pre_enabled = 0; /* To know whether to skip RMRR */
>  	for_each_active_iommu(iommu, drhd) {
>  		g_iommus[iommu->seq_id] = iommu;
>  
> @@ -2904,14 +2939,30 @@ static int __init init_dmars(void)
>  		if (ret)
>  			goto free_iommu;
>  
> -		/*
> -		 * TBD:
> -		 * we could share the same root & context tables
> -		 * among all IOMMU's. Need to Split it later.
> -		 */
> -		ret = iommu_alloc_root_entry(iommu);
> -		if (ret)
> -			goto free_iommu;
> +		iommu_check_pre_te_status(iommu);
> +		if (iommu->pre_enabled_trans) {
> +			pr_info("IOMMU Copying translate tables from panicked kernel\n");
> +			ret = intel_iommu_load_translation_tables(iommu);
> +			if (ret) {
> +				pr_err("IOMMU: Copy translate tables failed\n");
> +
> +				/* Best to stop trying */
> +				goto free_iommu;
> +			}
> +			pr_info("IOMMU: root_cache:0x%12.12llx phys:0x%12.12llx\n",
> +				(u64)iommu->root_entry,
> +				(u64)iommu->root_entry_old_phys);
> +		} else {
> +			/*
> +			 * TBD:
> +			 * we could share the same root & context tables
> +			 * among all IOMMU's. Need to Split it later.
> +			 */
> +			ret = iommu_alloc_root_entry(iommu);
> +			if (ret)
> +				goto free_iommu;
> +		}
> +
>  		if (!ecap_pass_through(iommu->ecap))
>  			hw_pass_through = 0;
>  	}
> @@ -2929,6 +2980,14 @@ static int __init init_dmars(void)
>  	check_tylersburg_isoch();
>  
>  	/*
> +	 * In the second kernel: Skip setting-up new domains for

Use kexec kernel instead of second kernel is better because there's no context
reader will be confused.

> +	 * si, rmrr, and the isa bus on the expectation that these
> +	 * translations were copied from the old kernel.
> +	 */
> +	if (g_translation_pre_enabled)
> +		goto skip_new_domains_for_si_rmrr_isa;
> +
> +	/*
>  	 * If pass through is not set or not enabled, setup context entries for
>  	 * identity mappings for rmrr, gfx, and isa and may fall back to static
>  	 * identity mapping if iommu_identity_mapping is set.
> @@ -2968,6 +3027,8 @@ static int __init init_dmars(void)
>  
>  	iommu_prepare_isa();
>  
> +skip_new_domains_for_si_rmrr_isa:;
> +
>  	/*
>  	 * for each drhd
>  	 *   enable fault log
> @@ -2996,7 +3057,13 @@ static int __init init_dmars(void)
>  
>  		iommu->flush.flush_context(iommu, 0, 0, 0, DMA_CCMD_GLOBAL_INVL);
>  		iommu->flush.flush_iotlb(iommu, 0, 0, 0, DMA_TLB_GLOBAL_FLUSH);
> -		iommu_enable_translation(iommu);
> +
> +		if (iommu->pre_enabled_trans) {
> +			if (!(iommu->gcmd & DMA_GCMD_TE))
> +				iommu_enable_translation(iommu);
> +		} else
> +			iommu_enable_translation(iommu);
> +
>  		iommu_disable_protect_mem_regions(iommu);
>  	}
>  
> @@ -4282,11 +4349,14 @@ int __init intel_iommu_init(void)
>  	}
>  
>  	/*
> -	 * Disable translation if already enabled prior to OS handover.
> +	 * We do not need to disable translation if already enabled prior
> +	 * to OS handover. Because we will try to copy old tables;
>  	 */
> +	/*
>  	for_each_active_iommu(iommu, drhd)
>  		if (iommu->gcmd & DMA_GCMD_TE)
>  			iommu_disable_translation(iommu);
> +	*/

Above commented out code is useless?

>  
>  	if (dmar_dev_scope_init() < 0) {
>  		if (force_on)
> @@ -5106,5 +5176,6 @@ static void iommu_check_pre_te_status(struct intel_iommu *iommu)
>  	if (sts & DMA_GSTS_TES) {
>  		pr_info("Translation is enabled prior to OS.\n");
>  		iommu->pre_enabled_trans = 1;
> +		g_translation_pre_enabled = 1;
>  	}
>  }
> -- 
> 2.0.0-rc0
> 
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