linux-kernel - Re: [PATCH v5 5/5] iommu/s390: allow larger region tables

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Message-ID: <925b1369de0d347ddee2115d1de63843623ac485.camel@linux.ibm.com>
Date: Wed, 16 Apr 2025 11:35:15 +0200
From: Niklas Schnelle <schnelle@...ux.ibm.com>
To: Matthew Rosato <mjrosato@...ux.ibm.com>, joro@...tes.org, will@...nel.org,
        robin.murphy@....com, gerald.schaefer@...ux.ibm.com
Cc: hca@...ux.ibm.com, gor@...ux.ibm.com, agordeev@...ux.ibm.com,
        svens@...ux.ibm.com, borntraeger@...ux.ibm.com, clg@...hat.com,
        iommu@...ts.linux.dev, linux-kernel@...r.kernel.org,
        linux-s390@...r.kernel.org
Subject: Re: [PATCH v5 5/5] iommu/s390: allow larger region tables

On Fri, 2025-04-11 at 16:24 -0400, Matthew Rosato wrote:
> Extend the aperture calculation to consider sizes beyond the maximum
> size of a region third table.  Attempt to always use the smallest
> table size possible to avoid unnecessary extra steps during translation.
> Update reserved region calculations to use the appropriate table size.
> 
> Signed-off-by: Matthew Rosato <mjrosato@...ux.ibm.com>
> ---
>  arch/s390/include/asm/pci_dma.h |  1 +
>  drivers/iommu/s390-iommu.c      | 70 ++++++++++++++++++++++++---------
>  2 files changed, 53 insertions(+), 18 deletions(-)
> 
> diff --git a/arch/s390/include/asm/pci_dma.h b/arch/s390/include/asm/pci_dma.h
> index 8d8962e4fd58..d12e17201661 100644
> --- a/arch/s390/include/asm/pci_dma.h
> +++ b/arch/s390/include/asm/pci_dma.h
> @@ -25,6 +25,7 @@ enum zpci_ioat_dtype {
>  #define ZPCI_KEY			(PAGE_DEFAULT_KEY << 5)
>  
>  #define ZPCI_TABLE_SIZE_RT	(1UL << 42)
> +#define ZPCI_TABLE_SIZE_RS	(1UL << 53)
>  
>  #define ZPCI_IOTA_STO_FLAG	(ZPCI_IOTA_IOT_ENABLED | ZPCI_KEY | ZPCI_IOTA_DT_ST)
>  #define ZPCI_IOTA_RTTO_FLAG	(ZPCI_IOTA_IOT_ENABLED | ZPCI_KEY | ZPCI_IOTA_DT_RT)
> diff --git a/drivers/iommu/s390-iommu.c b/drivers/iommu/s390-iommu.c
> index 46f45b136993..433b59f43530 100644
> --- a/drivers/iommu/s390-iommu.c
> +++ b/drivers/iommu/s390-iommu.c
> @@ -511,9 +511,25 @@ static bool s390_iommu_capable(struct device *dev, enum iommu_cap cap)
>  	}
>  }
>  
> +static inline u64 max_tbl_size(struct s390_domain *domain)
> +{
> +	switch (domain->origin_type) {
> +	case ZPCI_TABLE_TYPE_RTX:
> +		return ZPCI_TABLE_SIZE_RT - 1;
> +	case ZPCI_TABLE_TYPE_RSX:
> +		return ZPCI_TABLE_SIZE_RS - 1;
> +	case ZPCI_TABLE_TYPE_RFX:
> +		return U64_MAX;
> +	default:
> +		return 0;
> +	}
> +}
> +
>  static struct iommu_domain *s390_domain_alloc_paging(struct device *dev)
>  {
> +	struct zpci_dev *zdev = to_zpci_dev(dev);
>  	struct s390_domain *s390_domain;
> +	u64 aperture_size;
>  
>  	s390_domain = kzalloc(sizeof(*s390_domain), GFP_KERNEL);
>  	if (!s390_domain)
> @@ -524,10 +540,26 @@ static struct iommu_domain *s390_domain_alloc_paging(struct device *dev)
>  		kfree(s390_domain);
>  		return NULL;
>  	}
> +
> +	aperture_size = min(s390_iommu_aperture,
> +			    zdev->end_dma - zdev->start_dma + 1);
> +	if (aperture_size <= (ZPCI_TABLE_SIZE_RT - zdev->start_dma)) {
> +		s390_domain->origin_type = ZPCI_TABLE_TYPE_RTX;
> +	} else if (aperture_size <= (ZPCI_TABLE_SIZE_RS - zdev->start_dma) &&
> +		  (zdev->dtsm & ZPCI_IOTA_DT_RS)) {
> +		s390_domain->origin_type = ZPCI_TABLE_TYPE_RSX;
> +	} else if (zdev->dtsm & ZPCI_IOTA_DT_RF) {
> +		s390_domain->origin_type = ZPCI_TABLE_TYPE_RFX;
> +	} else {
> +		/* Assume RTX available */
> +		s390_domain->origin_type = ZPCI_TABLE_TYPE_RTX;
> +		aperture_size = ZPCI_TABLE_SIZE_RT - zdev->start_dma;
> +	}
> +	zdev->end_dma = zdev->start_dma + aperture_size - 1;
> +
>  	s390_domain->domain.geometry.force_aperture = true;
>  	s390_domain->domain.geometry.aperture_start = 0;
> -	s390_domain->domain.geometry.aperture_end = ZPCI_TABLE_SIZE_RT - 1;
> -	s390_domain->origin_type = ZPCI_TABLE_TYPE_RTX;
> +	s390_domain->domain.geometry.aperture_end = max_tbl_size(s390_domain);
>  
>  	spin_lock_init(&s390_domain->list_lock);
>  	INIT_LIST_HEAD_RCU(&s390_domain->devices);
> @@ -680,6 +712,8 @@ static void s390_iommu_get_resv_regions(struct device *dev,
>  {
>  	struct zpci_dev *zdev = to_zpci_dev(dev);
>  	struct iommu_resv_region *region;
> +	u64 max_size, end_resv;
> +	unsigned long flags;
>  
>  	if (zdev->start_dma) {
>  		region = iommu_alloc_resv_region(0, zdev->start_dma, 0,
> @@ -689,10 +723,21 @@ static void s390_iommu_get_resv_regions(struct device *dev,
>  		list_add_tail(&region->list, list);
>  	}
>  
> -	if (zdev->end_dma < ZPCI_TABLE_SIZE_RT - 1) {
> -		region = iommu_alloc_resv_region(zdev->end_dma + 1,
> -						 ZPCI_TABLE_SIZE_RT - zdev->end_dma - 1,
> -						 0, IOMMU_RESV_RESERVED, GFP_KERNEL);
> +	spin_lock_irqsave(&zdev->dom_lock, flags);
> +	if (zdev->s390_domain->type == IOMMU_DOMAIN_BLOCKED ||
> +	    zdev->s390_domain->type == IOMMU_DOMAIN_IDENTITY) {
> +		spin_unlock_irqrestore(&zdev->dom_lock, flags);
> +		return;
> +	}
> +
> +	max_size = max_tbl_size(to_s390_domain(zdev->s390_domain));
> +	spin_unlock_irqrestore(&zdev->dom_lock, flags);
> +
> +	if (zdev->end_dma < max_size) {
> +		end_resv = max_size - zdev->end_dma;
> +		region = iommu_alloc_resv_region(zdev->end_dma + 1, end_resv,
> +						 0, IOMMU_RESV_RESERVED,
> +						 GFP_KERNEL);
>  		if (!region)
>  			return;
>  		list_add_tail(&region->list, list);
> @@ -708,13 +753,9 @@ static struct iommu_device *s390_iommu_probe_device(struct device *dev)
>  
>  	zdev = to_zpci_dev(dev);
>  
> -	if (zdev->start_dma > zdev->end_dma ||
> -	    zdev->start_dma > ZPCI_TABLE_SIZE_RT - 1)
> +	if (zdev->start_dma > zdev->end_dma)
>  		return ERR_PTR(-EINVAL);
>  
> -	if (zdev->end_dma > ZPCI_TABLE_SIZE_RT - 1)
> -		zdev->end_dma = ZPCI_TABLE_SIZE_RT - 1;
> -
>  	if (zdev->tlb_refresh)
>  		dev->iommu->shadow_on_flush = 1;
>  
> @@ -999,7 +1040,6 @@ struct zpci_iommu_ctrs *zpci_get_iommu_ctrs(struct zpci_dev *zdev)
>  
>  int zpci_init_iommu(struct zpci_dev *zdev)
>  {
> -	u64 aperture_size;
>  	int rc = 0;
>  
>  	rc = iommu_device_sysfs_add(&zdev->iommu_dev, NULL, NULL,
> @@ -1017,12 +1057,6 @@ int zpci_init_iommu(struct zpci_dev *zdev)
>  	if (rc)
>  		goto out_sysfs;
>  
> -	zdev->start_dma = PAGE_ALIGN(zdev->start_dma);
> -	aperture_size = min3(s390_iommu_aperture,
> -			     ZPCI_TABLE_SIZE_RT - zdev->start_dma,
> -			     zdev->end_dma - zdev->start_dma + 1);
> -	zdev->end_dma = zdev->start_dma + aperture_size - 1;
> -
>  	return 0;
>  
>  out_sysfs:

Looks good, thanks for the great work!

Reviewed-by: Niklas Schnelle <schnelle@...ux.ibm.com>