Re: [RFC PATCH 14/15] PCI/P2PDMA: Introduce pci_mmap_p2pmem()

[Jason Gunthorpe]

On Fri, Nov 06, 2020 at 10:00:35AM -0700, Logan Gunthorpe wrote:
> Introduce pci_mmap_p2pmem() which is a helper to allocate and mmap
> a hunk of p2pmem into userspace.
> 
> Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
>  drivers/pci/p2pdma.c       | 104 +++++++++++++++++++++++++++++++++++++
>  include/linux/pci-p2pdma.h |   6 +++
>  2 files changed, 110 insertions(+)
> 
> diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
> index 9961e779f430..8eab53ac59ae 100644
> +++ b/drivers/pci/p2pdma.c
> @@ -16,6 +16,7 @@
>  #include <linux/genalloc.h>
>  #include <linux/memremap.h>
>  #include <linux/percpu-refcount.h>
> +#include <linux/pfn_t.h>
>  #include <linux/random.h>
>  #include <linux/seq_buf.h>
>  #include <linux/xarray.h>
> @@ -1055,3 +1056,106 @@ ssize_t pci_p2pdma_enable_show(char *page, struct pci_dev *p2p_dev,
>  	return sprintf(page, "%s\n", pci_name(p2p_dev));
>  }
>  EXPORT_SYMBOL_GPL(pci_p2pdma_enable_show);
> +
> +struct pci_p2pdma_map {
> +	struct kref ref;
> +	struct pci_dev *pdev;
> +	void *kaddr;
> +	size_t len;
> +};

Why have this at all? Nothing uses it and no vm_operations ops are
implemented?

This is very inflexable, it would be better if this is designed like
io_remap_pfn where it just preps and fills the VMA, doesn't take
ownership of the entire VMA

Jason