linux-kernel - Re: [PATCH v8 06/10] iommu/vt-d: datatypes and functions used for kdump

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Message-ID: <54B753EF.30609@hp.com>
Date:	Thu, 15 Jan 2015 13:45:19 +0800
From:	"Li, ZhenHua" <zhen-hual@...com>
To:	Baoquan He <bhe@...hat.com>
CC:	dwmw2@...radead.org, indou.takao@...fujitsu.com, joro@...tes.org,
	vgoyal@...hat.com, dyoung@...hat.com, jerry.hoemann@...com,
	tom.vaden@...com, rwright@...com, linux-pci@...r.kernel.org,
	kexec@...ts.infradead.org, iommu@...ts.linux-foundation.org,
	lisa.mitchell@...com, linux-kernel@...r.kernel.org,
	alex.williamson@...hat.com, ddutile@...hat.com, doug.hatch@...com,
	ishii.hironobu@...fujitsu.com, bhelgaas@...gle.com,
	billsumnerlinux@...il.com, li.zhang6@...com
Subject: Re: [PATCH v8 06/10] iommu/vt-d: datatypes and functions used for
 kdump

Hi Baoquan,
Thank you very much for your review. But according to the latest
discussion, the page tables will not be copied from old kernel. We keep
using the old page tables before driver is loaded. So there are many
changes in next version;

See my comments.

On 01/15/2015 11:28 AM, Baoquan He wrote:
> On 01/12/15 at 03:06pm, Li, Zhen-Hua wrote:
>> +/*
>> + * Interface to the "copy translation tables" set of functions
>> + * from mainline code.
>> + */
>> +static int intel_iommu_load_translation_tables(struct dmar_drhd_unit *drhd,
>> +		int g_num_of_iommus)
>
> The argument g_num_of_iommus is the same as the global variable, it's better
> to rename it as num_of_iommus. And even it can be removed since you can
> just use the global variable g_num_of_iommus in this function.
>
> Argument drhd can be intel_iommu because no other member variable in
> drhd is needed.

This function is no longer used. So forget the parameters.

>
>> +{
>> +	struct intel_iommu *iommu;	/* Virt(iommu hardware registers) */
>> +	unsigned long long q;		/* quadword scratch */
>> +	int ret = 0;			/* Integer return code */
>> +	int i = 0;			/* Loop index */
>> +	unsigned long flags;
>> +
>> +	/* Structure so copy_page_addr() can accumulate things
>> +	 * over multiple calls and returns
>> +	 */
>> +	struct copy_page_addr_parms ppa_parms = copy_page_addr_parms_init;
>> +	struct copy_page_addr_parms *ppap = &ppa_parms;
>> +
>> +
>> +	iommu = drhd->iommu;
>> +	q = dmar_readq(iommu->reg + DMAR_RTADDR_REG);
>> +	if (!q)
>> +		return -1;
>> +
>> +	/* If (list needs initializing) do it here */
>
> This initializing should not be here, because it's not only for this
> drhd. It should be done in init_dmars().
>
Yes you are right. Though the variable domain_values_list will not be
used in next version, I think I need to check if there are any other
similar problems.

>> +	if (!domain_values_list) {
>> +		domain_values_list =
>> +			 kcalloc(g_num_of_iommus, sizeof(struct list_head),
>> +					GFP_KERNEL);
>> +
>> +		if (!domain_values_list) {
>> +			pr_err("Allocation failed for domain_values_list array\n");
>> +			return -ENOMEM;
>> +		}
>> +		for (i = 0; i < g_num_of_iommus; i++)
>> +			INIT_LIST_HEAD(&domain_values_list[i]);
>> +	}
>> +
>> +	spin_lock_irqsave(&iommu->lock, flags);
>> +
>> +	/* Load the root-entry table from the old kernel
>> +	 * foreach context_entry_table in root_entry
>> +	 *    foreach context_entry in context_entry_table
>> +	 *       foreach level-1 page_table_entry in context_entry
>> +	 *          foreach level-2 page_table_entry in level 1 page_table_entry
>> +	 *             Above pattern continues up to 6 levels of page tables
>> +	 *                Sanity-check the entry
>> +	 *                Process the bus, devfn, page_address, page_size
>> +	 */
>> +	if (!iommu->root_entry) {
>> +		iommu->root_entry =
>> +			(struct root_entry *)alloc_pgtable_page(iommu->node);
>> +		if (!iommu->root_entry) {
>> +			spin_unlock_irqrestore(&iommu->lock, flags);
>> +			return -ENOMEM;
>> +		}
>> +	}
>> +
>> +	iommu->root_entry_old_phys = q & VTD_PAGE_MASK;
>> +	if (!iommu->root_entry_old_phys) {
>> +		pr_err("Could not read old root entry address.");
>> +		return -1;
>> +	}
>> +
>> +	iommu->root_entry_old_virt = ioremap_cache(iommu->root_entry_old_phys,
>> +						VTD_PAGE_SIZE);
>> +	if (!iommu->root_entry_old_virt) {
>> +		pr_err("Could not map the old root entry.");
>> +		return -ENOMEM;
>> +	}
>> +
>> +	__iommu_load_old_root_entry(iommu);
>> +	ret = copy_root_entry_table(iommu, ppap);
>> +	__iommu_flush_cache(iommu, iommu->root_entry, PAGE_SIZE);
>> +	__iommu_update_old_root_entry(iommu, -1);
>> +
>> +	spin_unlock_irqrestore(&iommu->lock, flags);
>> +
>> +	__iommu_free_mapped_mem();
>> +
>> +	if (ret)
>> +		return ret;
>> +
>> +	ppa_parms.last = 1;
>> +	copy_page_addr(0, 0, 0, 0, 0, NULL, ppap);
>> +
>> +	return 0;
>> +}
>> +
>>   #endif /* CONFIG_CRASH_DUMP */
>> --
>> 2.0.0-rc0
>>
>>
>> _______________________________________________
>> kexec mailing list
>> kexec@...ts.infradead.org
>> http://lists.infradead.org/mailman/listinfo/kexec

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