Re: [PATCH v5 13/24] iommu/amd: Program IOMMU DTE with the private IPA domain

[guanghuifeng@xxxxxxxxxxxxxxxxx]

在 2026/9/15 2:47, Suravee Suthikulpanit 写道:
> The IOMMU PCI function does not go through the normal device attach
> path, so it has no iommu_dev_data. Add amd_iommu_alloc_dev_data()
> and amd_iommu_free_dev_data() for a synthetic object that is not
> interned in pci_seg->dev_data_xa. Program that DTE with the private
> IPA domain's v1 page table so the IOMMU can DMA to its own vIOMMU
> backing store.
>
> Leave the synthetic DTE off pdom->dev_list and with no struct
> device so clone_aliases() is skipped; it is only iommu->devid.
> Rewrite it from amd_iommu_change_top() when the IPA table grows
> so later high maps remain reachable.
>
> Do this after viommu_private_space_init() so viommu_pdom exists.
> Clear the DTE and free the object on teardown. Failed self DTE
> allocation unwinds through amd_viommu_uninit().
>
> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
> ---
>   drivers/iommu/amd/amd_iommu.h       |   4 ++
>   drivers/iommu/amd/amd_iommu_types.h |   2 +
>   drivers/iommu/amd/iommu.c           | 102 +++++++++++++++++++++++++---
>   drivers/iommu/amd/viommu.c          |  48 +++++++++++++
>   4 files changed, 148 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/iommu/amd/amd_iommu.h b/drivers/iommu/amd/amd_iommu.h
> index 9cc5da745a73..6ac64524208b 100644
> --- a/drivers/iommu/amd/amd_iommu.h
> +++ b/drivers/iommu/amd/amd_iommu.h
> @@ -50,6 +50,10 @@ extern u8 amd_iommu_hpt_vasize;
>   extern unsigned long amd_iommu_pgsize_bitmap;
>   extern bool amd_iommu_hatdis;
>   
> +struct iommu_dev_data *amd_iommu_alloc_dev_data(u16 devid);
> +void amd_iommu_free_dev_data(struct amd_iommu *iommu,
> +			     struct iommu_dev_data *dev_data);
> +
>   /* Protection domain ops */
>   void amd_iommu_init_identity_domain(void);
>   struct protection_domain *protection_domain_alloc(void);
> diff --git a/drivers/iommu/amd/amd_iommu_types.h b/drivers/iommu/amd/amd_iommu_types.h
> index d02f49a39a90..4b48ec8bacd6 100644
> --- a/drivers/iommu/amd/amd_iommu_types.h
> +++ b/drivers/iommu/amd/amd_iommu_types.h
> @@ -814,6 +814,8 @@ struct amd_iommu {
>   	struct ida gid_ida;		 /* guest IDs for this IOMMU */
>   
>   	/* HW vIOMMU support */
> +	/* Synthetic IOMMU-self DTE; not in pci_seg->dev_data_xa or pdom->dev_list */
> +	struct iommu_dev_data *viommu_dev_data;
>   	struct protection_domain *viommu_pdom;
>   	void *viommu_priv_region[VIOMMU_PRIV_SUBREGION_CNT];
>   };
> diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
> index 2b039f38f9ef..bcbd5af75d00 100644
> --- a/drivers/iommu/amd/iommu.c
> +++ b/drivers/iommu/amd/iommu.c
> @@ -217,7 +217,12 @@ void amd_iommu_update_dte(struct amd_iommu *iommu,
>   			     struct dev_table_entry *new)
>   {
>   	update_dte256(iommu, dev_data, new);
> -	clone_aliases(iommu, dev_data->dev);
> +	/*
> +	 * Synthetic DTEs (vIOMMU self, translate-device-id) leave
> +	 * dev_data->dev NULL so clone_aliases() is skipped.
> +	 */
> +	if (dev_data->dev)
> +		clone_aliases(iommu, dev_data->dev);
>   	device_flush_dte(iommu, dev_data);
>   	iommu_completion_wait(iommu);
>   }
> @@ -391,14 +396,13 @@ static struct amd_iommu *rlookup_amd_iommu(struct device *dev)
>   }
>   
>   /*
> - * Allocate an immortal per-devid object stored in pci_seg->dev_data_xa.
> - * These are never erased: amd_iommu_release_device() keeps them for
> - * replug, and IRQ/DTE paths look them up locklessly via xa_load().
> + * Allocate a synthetic DTE object that is not inserted into
> + * pci_seg->dev_data_xa. Lifetime is owned by the caller (vIOMMU
> + * self DTE or translate-device-id).
>    */
> -static struct iommu_dev_data *alloc_dev_data(struct amd_iommu *iommu, u16 devid)
> +struct iommu_dev_data *amd_iommu_alloc_dev_data(u16 devid)
>   {
> -	struct iommu_dev_data *dev_data, *old;
> -	struct amd_iommu_pci_seg *pci_seg = iommu->pci_seg;
> +	struct iommu_dev_data *dev_data;
>   
>   	dev_data = kzalloc_obj(*dev_data);
>   	if (!dev_data)
> @@ -408,6 +412,22 @@ static struct iommu_dev_data *alloc_dev_data(struct amd_iommu *iommu, u16 devid)
>   	spin_lock_init(&dev_data->dte_lock);
>   	dev_data->devid = devid;
>   	ratelimit_default_init(&dev_data->rs);
> +	return dev_data;
> +}
> +
> +/*
> + * Allocate an immortal per-devid object stored in pci_seg->dev_data_xa.
> + * These are never erased: amd_iommu_release_device() keeps them for
> + * replug, and IRQ/DTE paths look them up locklessly via xa_load().
> + */
> +static struct iommu_dev_data *alloc_dev_data(struct amd_iommu *iommu, u16 devid)
> +{
> +	struct iommu_dev_data *dev_data, *old;
> +	struct amd_iommu_pci_seg *pci_seg = iommu->pci_seg;
> +
> +	dev_data = amd_iommu_alloc_dev_data(devid);
> +	if (!dev_data)
> +		return NULL;
>   
>   	old = xa_cmpxchg(&pci_seg->dev_data_xa, devid, NULL, dev_data,
>   			 GFP_KERNEL);
> @@ -428,6 +448,22 @@ struct iommu_dev_data *search_dev_data(struct amd_iommu *iommu, u16 devid)
>   	return xa_load(&iommu->pci_seg->dev_data_xa, devid);
>   }
>   
> +void amd_iommu_free_dev_data(struct amd_iommu *iommu,
> +			     struct iommu_dev_data *dev_data)
> +{
> +	if (!dev_data)
> +		return;
> +
> +	/*
> +	 * PCI/alias objects in the xarray are immortal. Never kfree
> +	 * those; synthetics must not be stored there.
> +	 */
> +	if (WARN_ON_ONCE(search_dev_data(iommu, dev_data->devid) == dev_data))
> +		return;
> +
> +	kfree(dev_data);
> +}
> +
>   static int clone_alias(struct pci_dev *pdev_origin, u16 alias, void *data)
>   {
>   	struct dev_table_entry new;
> @@ -1826,7 +1862,11 @@ static int device_flush_dte(struct amd_iommu *iommu, struct iommu_dev_data *dev_
>   	u16 alias;
>   	int ret;
>   
> -	if (dev_is_pci(dev_data->dev))
> +	/*
> +	 * Synthetic DTEs leave dev_data->dev NULL; flush iommu->devid
> +	 * rather than walking PCI DMA aliases.
> +	 */
> +	if (dev_data->dev && dev_is_pci(dev_data->dev))
>   		pdev = to_pci_dev(dev_data->dev);
>   
>   	if (pdev)
> @@ -2770,6 +2810,51 @@ static spinlock_t *amd_iommu_get_top_lock(struct pt_iommu *iommupt)
>   	return &pdom->lock;
>   }
>   
> +#if IS_ENABLED(CONFIG_AMD_IOMMU_IOMMUFD)
> +/*
> + * The vIOMMU private IPA domain programs a synthetic DTE for the
> + * IOMMU's own requester ID so hardware can DMA to backing store.
> + * That object is not on pdom->dev_list: it is not an IOMMU-API
> + * attach, and walkers such as rlookup and clone_aliases assume a
> + * real struct device.
> + *
> + * amd_iommu_change_top() therefore misses it. Early maps fit under
> + * the initial page-table top (PT_FEAT_DYNAMIC_TOP). Later DevID and
> + * DomID maps at high IPA call increase_top(); the old root stays
> + * live as a child of the new one, but the self DTE still holds the
> + * old MODE and would not translate those IOVAs.
> + *
> + * Walk iommu_array (from amd_iommu_pdom_bind_iommu()) and rewrite
> + * iommu->viommu_dev_data when this domain is that IOMMU's private
> + * IPA table. set_dte_entry() skips clone_aliases() because the
> + * synthetic DTE has no struct device.
> + */
> +static void update_viommu_self_dte(struct protection_domain *pdom,
> +				   phys_addr_t top_paddr,
> +				   unsigned int top_level)
> +{
> +	struct pdom_iommu_info *pdom_iommu_info;
> +	unsigned long i;
> +
> +	lockdep_assert_held(&pdom->lock);
> +
> +	xa_for_each(&pdom->iommu_array, i, pdom_iommu_info) {
> +		struct amd_iommu *iommu = pdom_iommu_info->iommu;
> +
> +		if (iommu->viommu_pdom != pdom || !iommu->viommu_dev_data)
> +			continue;
> +		set_dte_entry(iommu, iommu->viommu_dev_data, top_paddr,
> +			      top_level);
> +	}
> +}

Self DTE Mode maybe does not comply with spec requirement of Mode=100b

At initialization time, only the 8MB General Backing Storage region (IPA 
0x0 - 0x800000) is mapped, so the page table top is likely level 1 or 2, 
resulting in Mode = 010b or 011b.

However, spec Section 2.10.1 states explicitly:
"The DTE for the IOMMU's DeviceID must be set with V=1, TV=1, GV=0, 
Mode=100b."

This is a hard requirement ("must"), not a recommendation. Mode=100b 
means 4-level page table (48-bit address space), which is necessary 
because the private IPA address map extends up to 48'h0050_0000_0000 
(~5TB), well beyond the 39-bit limit of a 3-level table.


> +#else
> +static inline void update_viommu_self_dte(struct protection_domain *pdom,
> +					  phys_addr_t top_paddr,
> +					  unsigned int top_level)
> +{
> +}
> +#endif
> +
>   /*
>    * Update all HW references to the domain with a new pgtable configuration.
>    */
> @@ -2792,6 +2877,7 @@ static void amd_iommu_change_top(struct pt_iommu *iommu_table,
>   		device_flush_dte(iommu, dev_data);
>   	}
>   
> +	update_viommu_self_dte(pdom, top_paddr, top_level);
>   	domain_flush_complete(pdom);
>   }
>   
> diff --git a/drivers/iommu/amd/viommu.c b/drivers/iommu/amd/viommu.c
> index 89d6dc520b2c..3ec907a498c2 100644
> --- a/drivers/iommu/amd/viommu.c
> +++ b/drivers/iommu/amd/viommu.c
> @@ -40,11 +40,55 @@ static void __init amd_viommu_vf_vfcntl_unmap(struct amd_iommu *iommu)
>   	}
>   }
>   
> +
> +static void viommu_free_self_dev_data(struct amd_iommu *iommu)
> +{
> +	struct iommu_dev_data *dev_data = iommu->viommu_dev_data;
> +	struct dev_table_entry new = {};
> +
> +	if (!dev_data)
> +		return;
> +
> +	amd_iommu_make_clear_dte(iommu, dev_data->devid, &new);
> +	amd_iommu_update_dte(iommu, dev_data, &new);
> +	amd_iommu_free_dev_data(iommu, dev_data);
> +	iommu->viommu_dev_data = NULL;
> +}
> +
> +static int viommu_alloc_self_dev_data(struct amd_iommu *iommu)
> +{
> +	struct protection_domain *pdom = iommu->viommu_pdom;
> +	struct pt_iommu_amdv1_hw_info pt_info;
> +	struct iommu_dev_data *dev_data;
> +	struct dev_table_entry new = {};
> +
> +	dev_data = amd_iommu_alloc_dev_data(iommu->devid);
> +	if (!dev_data) {
> +		pr_err("%s: Failed to allocate dev_data\n", __func__);
> +		return -ENOMEM;
> +	}
> +	/*
> +	 * Synthetic DTE for iommu->devid only: no struct device, so
> +	 * amd_iommu_update_dte() skips clone_aliases(), and not on
> +	 * pdom->dev_list (not an IOMMU-API attach).
> +	 */
> +	dev_data->dev = NULL;
> +	dev_data->domain = pdom;
> +	iommu->viommu_dev_data = dev_data;
> +
> +	amd_iommu_make_clear_dte(iommu, iommu->devid, &new);
> +	pt_iommu_amdv1_hw_info(&pdom->amdv1, &pt_info);
> +	amd_iommu_set_dte_v1(dev_data, pdom, pdom->id, &pt_info, &new);
> +	amd_iommu_update_dte(iommu, dev_data, &new);
> +	return 0;
> +}
> +
>   static void viommu_private_space_uninit(struct amd_iommu *iommu);
>   
>   void __init amd_viommu_uninit(struct amd_iommu *iommu)
>   {
>   	iommu->flags &= ~AMD_IOMMU_FLAG_VIOMMU_EN;
> +	viommu_free_self_dev_data(iommu);
>   	viommu_private_space_uninit(iommu);
>   	amd_viommu_vf_vfcntl_unmap(iommu);
>   }
> @@ -319,6 +363,10 @@ int __init amd_viommu_init(struct amd_iommu *iommu)
>   	if (ret)
>   		goto err;
>   
> +	ret = viommu_alloc_self_dev_data(iommu);
> +	if (ret)
> +		goto err;
> +
>   	iommu->flags |= AMD_IOMMU_FLAG_VIOMMU_EN;
>   	return 0;
>   err: