linux-kernel - Re: [PATCH 1/9] iommu: Move iommu fault data to linux/iommu.h

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Date:   Wed, 12 Jul 2023 10:07:22 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     "Tian, Kevin" <kevin.tian@...el.com>,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Nicolin Chen <nicolinc@...dia.com>
Cc:     baolu.lu@...ux.intel.com, "Liu, Yi L" <yi.l.liu@...el.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/9] iommu: Move iommu fault data to linux/iommu.h

On 2023/7/11 14:05, Tian, Kevin wrote:
>> From: Lu Baolu <baolu.lu@...ux.intel.com>
>> Sent: Tuesday, July 11, 2023 9:07 AM
>> +
>> +enum iommu_fault_reason {
>> +	IOMMU_FAULT_REASON_UNKNOWN = 0,
>> +
>> +	/* Could not access the PASID table (fetch caused external abort) */
>> +	IOMMU_FAULT_REASON_PASID_FETCH,
>> +
>> +	/* PASID entry is invalid or has configuration errors */
>> +	IOMMU_FAULT_REASON_BAD_PASID_ENTRY,
>> +
>> +	/*
>> +	 * PASID is out of range (e.g. exceeds the maximum PASID
>> +	 * supported by the IOMMU) or disabled.
>> +	 */
>> +	IOMMU_FAULT_REASON_PASID_INVALID,
>> +
>> +	/*
>> +	 * An external abort occurred fetching (or updating) a translation
>> +	 * table descriptor
>> +	 */
>> +	IOMMU_FAULT_REASON_WALK_EABT,
>> +
>> +	/*
>> +	 * Could not access the page table entry (Bad address),
>> +	 * actual translation fault
>> +	 */
>> +	IOMMU_FAULT_REASON_PTE_FETCH,
>> +
>> +	/* Protection flag check failed */
>> +	IOMMU_FAULT_REASON_PERMISSION,
>> +
>> +	/* access flag check failed */
>> +	IOMMU_FAULT_REASON_ACCESS,
>> +
>> +	/* Output address of a translation stage caused Address Size fault */
>> +	IOMMU_FAULT_REASON_OOR_ADDRESS,
>> +};
>> +
>> +/**
>> + * struct iommu_fault_unrecoverable - Unrecoverable fault data
>> + * @reason: reason of the fault, from &enum iommu_fault_reason
>> + * @flags: parameters of this fault (IOMMU_FAULT_UNRECOV_* values)
>> + * @pasid: Process Address Space ID
>> + * @perm: requested permission access using by the incoming transaction
>> + *        (IOMMU_FAULT_PERM_* values)
>> + * @addr: offending page address
>> + * @fetch_addr: address that caused a fetch abort, if any
>> + */
>> +struct iommu_fault_unrecoverable {
>> +	__u32	reason;
>> +#define IOMMU_FAULT_UNRECOV_PASID_VALID		(1 << 0)
>> +#define IOMMU_FAULT_UNRECOV_ADDR_VALID		(1 << 1)
>> +#define IOMMU_FAULT_UNRECOV_FETCH_ADDR_VALID	(1 << 2)
>> +	__u32	flags;
>> +	__u32	pasid;
>> +	__u32	perm;
>> +	__u64	addr;
>> +	__u64	fetch_addr;
>> +};
> 
> Currently there is no handler for unrecoverable faults.
> 
> Both Intel/ARM register iommu_queue_iopf() as the device fault handler.
> It returns -EOPNOTSUPP for unrecoverable faults.
> 
> In your series the common iommu_handle_io_pgfault() also only works
> for PRQ.
> 
> It kinds of suggest above definitions are dead code, though arm-smmu-v3
> does attempt to set them.
> 
> Probably it's right time to remove them.
> 
> In the future even if there might be a need of forwarding unrecoverable
> faults to the user via iommufd, fault reasons reported by the physical
> IOMMU doesn't make any sense to the guest. Presumably the vIOMMU
> should walk guest configurations to set a fault reason which makes sense
> from guest p.o.v.

I am fine to remove unrecoverable faults data. But it was added by Jean,
so I'd like to know his opinion on this.

Best regards,
baolu