On Fri, Nov 06, 2020 at 10:28:00AM -0700, Logan Gunthorpe wrote: > > > On 2020-11-06 10:22 a.m., Jason Gunthorpe wrote: > > 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? > > It's necessary to free the allocated p2pmem when the mapping is torn down. That's suspicious.. Once in a VMA the lifetime of the page must be controlled by the page refcount, it can't be put back into the genpool just because the vma was destroed. Jason