linux-kernel - Re: [PATCHv3 3/6] Crashdump-Accepting-Active-IOMMU-Domain-Interfaces

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Date:	Tue, 4 Mar 2014 15:59:15 +0100
From:	Joerg Roedel <joro@...tes.org>
To:	Bill Sumner <bill.sumner@...com>
Cc:	dwmw2@...radead.org, indou.takao@...fujitsu.com, bhe@...hat.com,
	iommu@...ts.linux-foundation.org, kexec@...ts.infradead.org,
	alex.williamson@...hat.com, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, ddutile@...hat.com,
	ishii.hironobu@...fujitsu.com, bhelgaas@...gle.com,
	doug.hatch@...com, zhenhua@...com
Subject: Re: [PATCHv3 3/6] Crashdump-Accepting-Active-IOMMU-Domain-Interfaces

On Fri, Jan 10, 2014 at 03:07:29PM -0700, Bill Sumner wrote:
> +context_get_entry(struct context_entry *context_addr,
> +			struct intel_iommu *iommu, u32 bus, int devfn)
> +{
> +	unsigned long long q;		/* quadword scratch */
> +	struct root_entry *root_phys;	/* Phys adr (root table entry) */
> +	struct root_entry  root_temp;	/* Local copy of root_entry */
> +	struct context_entry *context_phys;	/* Phys adr */
> +
> +	if (pr_dbg.domain_get)
> +		pr_debug("ENTER %s B:D:F=%2.2x:%2.2x:%1.1x &context_entry:0x%llx &intel_iommu:0x%llx\n",
> +			__func__, bus, devfn>>3, devfn&7,
> +			(u64)context_addr, (u64)iommu);
> +
> +	if (bus > 255)				/* Sanity check */
> +		return -5;
> +	if (devfn > 255 || devfn < 0)		/* Sanity check */
> +		return -6;
> +
> +	q = readq(iommu->reg + DMAR_RTADDR_REG);
> +	pr_debug("IOMMU %d: DMAR_RTADDR_REG:0x%16.16llx\n", iommu->seq_id, q);
> +	if (!q)
> +		return -1;
> +
> +	root_phys = (struct root_entry *) q;	/* Adr(base of vector) */
> +	root_phys += bus;			/* Adr(entry we want) */
> +
> +	oldcopy(&root_temp, root_phys, sizeof(root_temp));
> +
> +	pr_debug("root_temp.val:0x%llx .rsvd1:0x%llx root_phys:0x%llx\n",
> +		root_temp.val, root_temp.rsvd1, (u64)root_phys);
> +
> +	if (!root_present(&root_temp))
> +		return -2;
> +
> +	pr_debug("B:D:F=%2.2x:%2.2x:%1.1x root_temp.val: %llx .rsvd1: %llx\n",
> +		bus, devfn >> 3, devfn & 7, root_temp.val, root_temp.rsvd1);
> +
> +	if (root_temp.rsvd1)			/* If (root_entry is bad) */
> +		return -3;
> +
> +	context_phys = get_context_phys_from_root(&root_temp);
> +	if (!context_phys)
> +		return -4;

What do all these magic return values mean? 


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