Re: [PATCH v5 6/6] iommu/s390: Implement map_pages()/unmap_pages() instead of map()/unmap()

[Matthew Rosato <mjrosato@linux.ibm.com>]

On 10/6/22 10:47 AM, Niklas Schnelle wrote:
> While s390-iommu currently implements the map_page()/unmap_page()
> operations which only map/unmap a single page at a time the internal
> s390_iommu_update_trans() API already supports mapping/unmapping a range
> of pages at once. Take advantage of this by implementing the
> map_pages()/unmap_pages() operations instead thus allowing users of the
> IOMMU drivers to map multiple pages in a single call followed by
> a single I/O TLB flush if needed.
> 
> Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
> ---
>  drivers/iommu/s390-iommu.c | 48 +++++++++++++++++++++++++-------------
>  1 file changed, 32 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/iommu/s390-iommu.c b/drivers/iommu/s390-iommu.c
> index ac200f0b81fa..7b92855135ac 100644
> --- a/drivers/iommu/s390-iommu.c
> +++ b/drivers/iommu/s390-iommu.c
> @@ -189,20 +189,15 @@ static void s390_iommu_release_device(struct device *dev)
>  
>  static int s390_iommu_update_trans(struct s390_domain *s390_domain,
>  				   phys_addr_t pa, dma_addr_t dma_addr,
> -				   size_t size, int flags)
> +				   unsigned long nr_pages, int flags)
>  {
>  	phys_addr_t page_addr = pa & PAGE_MASK;
>  	dma_addr_t start_dma_addr = dma_addr;
> -	unsigned long irq_flags, nr_pages, i;
> +	unsigned long irq_flags, i;
>  	struct zpci_dev *zdev;
>  	unsigned long *entry;
>  	int rc = 0;
>  
> -	if (dma_addr < s390_domain->domain.geometry.aperture_start ||
> -	    (dma_addr + size - 1) > s390_domain->domain.geometry.aperture_end)
> -		return -EINVAL;
> -
> -	nr_pages = PAGE_ALIGN(size) >> PAGE_SHIFT;
>  	if (!nr_pages)
>  		return 0;
>  
> @@ -245,11 +240,24 @@ static int s390_iommu_update_trans(struct s390_domain *s390_domain,
>  	return rc;
>  }
>  
> -static int s390_iommu_map(struct iommu_domain *domain, unsigned long iova,
> -			  phys_addr_t paddr, size_t size, int prot, gfp_t gfp)
> +static int s390_iommu_map_pages(struct iommu_domain *domain,
> +				unsigned long iova, phys_addr_t paddr,
> +				size_t pgsize, size_t pgcount,
> +				int prot, gfp_t gfp, size_t *mapped)
>  {
>  	struct s390_domain *s390_domain = to_s390_domain(domain);
>  	int flags = ZPCI_PTE_VALID, rc = 0;
> +	size_t size = pgcount << __ffs(pgsize);
> +
> +	if (pgsize != SZ_4K)
> +		return -EINVAL;
> +
> +	if (iova < s390_domain->domain.geometry.aperture_start ||
> +	    (iova + size - 1) > s390_domain->domain.geometry.aperture_end)
> +		return -EINVAL;
> +
> +	if (!IS_ALIGNED(iova | paddr, pgsize))
> +		return -EINVAL;
>  
>  	if (!(prot & IOMMU_READ))
>  		return -EINVAL;
> @@ -258,7 +266,9 @@ static int s390_iommu_map(struct iommu_domain *domain, unsigned long iova,
>  		flags |= ZPCI_TABLE_PROTECTED;
>  
>  	rc = s390_iommu_update_trans(s390_domain, paddr, iova,
> -				     size, flags);
> +				     pgcount, flags);
> +	if (!rc)
> +		*mapped = size;
>  
>  	return rc;
>  }
> @@ -294,21 +304,27 @@ static phys_addr_t s390_iommu_iova_to_phys(struct iommu_domain *domain,
>  	return phys;
>  }
>  
> -static size_t s390_iommu_unmap(struct iommu_domain *domain,
> -			       unsigned long iova, size_t size,
> -			       struct iommu_iotlb_gather *gather)
> +static size_t s390_iommu_unmap_pages(struct iommu_domain *domain,
> +				     unsigned long iova,
> +				     size_t pgsize, size_t pgcount,
> +				     struct iommu_iotlb_gather *gather)
>  {
>  	struct s390_domain *s390_domain = to_s390_domain(domain);
> +	size_t size = pgcount << __ffs(pgsize);
>  	int flags = ZPCI_PTE_INVALID;
>  	phys_addr_t paddr;
>  	int rc;
>  
> +	if (iova < s390_domain->domain.geometry.aperture_start ||
> +	    (iova + size - 1) > s390_domain->domain.geometry.aperture_end)
> +		return 0;
> +

Overall this LGTM and runs well with my testing.  But I'm curious why we silently ignore an egregiously bad unmap request here?  We've already done an -EINVAL for an attempt to map_pages() something outside of the aperture.  If something still tries to unmap_pages() outside of the aperture, that seems like a bug?  Maybe this should be surrounded by a if (WARN_ON(... || ...) to signify the unexpected behavior and then still return 0?

Otherwise:
Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>

>  	paddr = s390_iommu_iova_to_phys(domain, iova);
>  	if (!paddr)
>  		return 0;
>  
>  	rc = s390_iommu_update_trans(s390_domain, paddr, iova,
> -				     size, flags);
> +				     pgcount, flags);
>  	if (rc)
>  		return 0;
>  
> @@ -354,8 +370,8 @@ static const struct iommu_ops s390_iommu_ops = {
>  	.default_domain_ops = &(const struct iommu_domain_ops) {
>  		.attach_dev	= s390_iommu_attach_device,
>  		.detach_dev	= s390_iommu_detach_device,
> -		.map		= s390_iommu_map,
> -		.unmap		= s390_iommu_unmap,
> +		.map_pages	= s390_iommu_map_pages,
> +		.unmap_pages	= s390_iommu_unmap_pages,
>  		.iova_to_phys	= s390_iommu_iova_to_phys,
>  		.free		= s390_domain_free,
>  	}