Re: [RFC PATCH v2 21/22] pci: Allow encrypted MMIO mapping via sysfs

[Bjorn Helgaas <helgaas@kernel.org>]

On Tue, Feb 18, 2025 at 10:10:08PM +1100, Alexey Kardashevskiy wrote:
> Add another resource#d_enc to allow mapping MMIO as
> an encrypted/private region.

I guess this means a sysfs file.  Document alongside the others.

> Unlike resourceN_wc, the node is added always as ability to
> map MMIO as private depends on negotiation with the TSM which
> happens quite late.

Match capitalization (subject) and wrap to fill 75 columns.

> +++ b/include/linux/pci.h
> @@ -2129,7 +2129,7 @@ pci_alloc_irq_vectors(struct pci_dev *dev, unsigned int min_vecs,
>   */
>  int pci_mmap_resource_range(struct pci_dev *dev, int bar,
>  			    struct vm_area_struct *vma,
> -			    enum pci_mmap_state mmap_state, int write_combine);
> +			    enum pci_mmap_state mmap_state, int write_combine, int enc);

Wrap to fit in 80 columns.

>  
>  #ifndef arch_can_pci_mmap_wc
>  #define arch_can_pci_mmap_wc()		0
> diff --git a/drivers/pci/mmap.c b/drivers/pci/mmap.c
> index 8da3347a95c4..4fd522aeb767 100644
> --- a/drivers/pci/mmap.c
> +++ b/drivers/pci/mmap.c
> @@ -23,7 +23,7 @@ static const struct vm_operations_struct pci_phys_vm_ops = {
>  
>  int pci_mmap_resource_range(struct pci_dev *pdev, int bar,
>  			    struct vm_area_struct *vma,
> -			    enum pci_mmap_state mmap_state, int write_combine)
> +			    enum pci_mmap_state mmap_state, int write_combine, int enc)

Ditto.

>  {
>  	unsigned long size;
>  	int ret;
> @@ -46,6 +46,15 @@ int pci_mmap_resource_range(struct pci_dev *pdev, int bar,
>  
>  	vma->vm_ops = &pci_phys_vm_ops;
>  
> +	/*
> +	 * Calling remap_pfn_range() directly as io_remap_pfn_range()
> +	 * enforces shared mapping.

s/Calling/Call/

> +	 */
> +	if (enc)
> +		return remap_pfn_range(vma, vma->vm_start, vma->vm_pgoff,
> +				       vma->vm_end - vma->vm_start,
> +				       vma->vm_page_prot);
> +
>  	return io_remap_pfn_range(vma, vma->vm_start, vma->vm_pgoff,
>  				  vma->vm_end - vma->vm_start,
>  				  vma->vm_page_prot);