linux-kernel - Re: [RFC 6/7] iommu/core: add fault reporting

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Date:	Mon, 5 Sep 2011 12:00:53 +0200
From:	"Roedel, Joerg" <Joerg.Roedel@....com>
To:	Ohad Ben-Cohen <ohad@...ery.com>
CC:	"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	Hiroshi DOYU <Hiroshi.DOYU@...ia.com>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	David Woodhouse <dwmw2@...radead.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	David Brown <davidb@...eaurora.org>,
	Arnd Bergmann <arnd@...db.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC 6/7] iommu/core: add fault reporting

On Fri, Sep 02, 2011 at 01:32:35PM -0400, Ohad Ben-Cohen wrote:
> -struct iommu_domain *iommu_domain_alloc(void)
> +/**
> + * iommu_domain_alloc() - allocate and initialize a new iommu domain
> + * @handler: an optional pointer to a fault handler, or NULL if not needed
> + *
> + * Returns the new domain, or NULL on error.
> + */
> +struct iommu_domain *iommu_domain_alloc(iommu_fault_handler_t handler)

Please add a seperate function for setting the fault-handler. It is
optional, so no need to be a value of the alloc-function.

> +/**
> + * enum iommu_fault_types - iommu fault types
> + *
> + * @IOMMU_ERROR: Unrecoverable error
> + * @IOMMU_TLBMISS: TLB miss while the page table walker is disabled
> + * @IOMMU_NOPTE: TLB miss and no PTE for the requested address
> + */
> +enum iommu_fault_types {
> +	IOMMU_ERROR,
> +	IOMMU_TLBMISS,
> +	IOMMU_NOPTE,
> +};

Can you elaborate a bit on what the user of the api will do different
between IOMMU_TLBMISS and IOMMU_NOPTE?
My feeling is that those differences should be handled internally in the
IOMMU driver, but probably I miss a use-case.
Also, we need some flags to distinguish between the type of the fault
(read, write, ...).

	Joerg


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