From 3a92c319c44a7bcee9f48dff9d97d001943b54c6 Mon Sep 17 00:00:00 2001 From: Bjorn Helgaas Date: Wed, 8 Jun 2016 14:46:54 -0500 Subject: [PATCH] PCI: Ignore write combining when mapping I/O port space PCI exposes files like /proc/bus/pci/00/00.0 in procfs. These files support operations like this: ioctl(fd, PCIIOC_MMAP_IS_IO); # request I/O port space ioctl(fd, PCIIOC_WRITE_COMBINE, 1); # request write-combining mmap(fd, ...) Write combining is useful on PCI memory space, but I don't think it makes sense on PCI I/O port space. We *could* change proc_bus_pci_ioctl() to make it impossible to set mmap_state == pci_mmap_io and write_combine at the same time, but that would break the following sequence, which is currently legal: mmap(fd, ...) # default is I/O, non-combining ioctl(fd, PCIIOC_WRITE_COMBINE, 1); # request write-combining ioctl(fd, PCIIOC_MMAP_IS_MEM); # request memory space mmap(fd, ...) # get write-combining mapping Ignore the write-combining flag when mapping I/O port space. This patch should have no functional effect, based on this analysis of all implementations of pci_mmap_page_range(): - ia64 mips parisc sh unicore32 x86 do not support mapping of I/O port space at all. - arm cris microblaze mn10300 sparc xtensa support mapping of I/O port space, but ignore the write_combine argument to pci_mmap_page_range(). - powerpc supports mapping of I/O port space and uses write_combine, and it disables write combining for I/O port space in __pci_mmap_set_pgprot(). This patch makes it possible to remove __pci_mmap_set_pgprot() from powerpc, which simplifies that path. Signed-off-by: Bjorn Helgaas --- drivers/pci/proc.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/drivers/pci/proc.c b/drivers/pci/proc.c index 3f155e78513f..2408abe4ee8c 100644 --- a/drivers/pci/proc.c +++ b/drivers/pci/proc.c @@ -231,7 +231,7 @@ static int proc_bus_pci_mmap(struct file *file, struct vm_area_struct *vma) { struct pci_dev *dev = PDE_DATA(file_inode(file)); struct pci_filp_private *fpriv = file->private_data; - int i, ret; + int i, ret, write_combine; if (!capable(CAP_SYS_RAWIO)) return -EPERM; @@ -245,9 +245,12 @@ static int proc_bus_pci_mmap(struct file *file, struct vm_area_struct *vma) if (i >= PCI_ROM_RESOURCE) return -ENODEV; + if (fpriv->mmap_state == pci_mmap_mem) + write_combine = fpriv->write_combine; + else + write_combine = 0; ret = pci_mmap_page_range(dev, vma, - fpriv->mmap_state, - fpriv->write_combine); + fpriv->mmap_state, write_combine); if (ret < 0) return ret; -- 2.20.1