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

[Baolu Lu]

On 2023/7/11 14:05, Tian, Kevin wrote:
> > From: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> > 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