Date:	Wed, 4 May 2016 10:17:22 -0500
From:	Bjorn Helgaas <helgaas@...nel.org>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	David Miller <davem@...emloft.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Wei Yang <weiyang@...ux.vnet.ibm.com>, TJ <linux@....tj>,
	Yijing Wang <wangyijing@...wei.com>,
	Khalid Aziz <khalid.aziz@...cle.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [PATCH v11 04/60] sparc/PCI: Use correct offset for bus address
 to resource

On Tue, May 03, 2016 at 10:52:33PM -0700, Yinghai Lu wrote:
> On Tue, May 3, 2016 at 10:08 PM, Yinghai Lu <yinghai@...nel.org> wrote:
> > On Tue, May 3, 2016 at 6:25 PM, Bjorn Helgaas <helgaas@...nel.org> wrote:
> >> I did not propose changing any user-visible ABI.  To recap what I did
> >> propose:
> >
> > I want to avoid introduce one strange pci_user_to_resource.
> >
> >>
> >>   - The sysfs path uses offsets between 0 and BAR size on all arches.
> >>     It uses pci_resource_to_user() today, but I think it should not.
> >>
> >>   - The procfs path uses offsets of resource values (CPU physical
> >>     addresses) on most architectures, but uses something else, e.g.,
> >>     BAR values, on others.  pci_resource_to_user() does this
> >>     translation.  The procfs path does not use pci_resource_to_user()
> >>     today, but I think it should.
> >
> > current powerpc pci_resource_to_user is strange:
> > it will return resource start for io mem.
> > but will return BAR (?) start for io port.
> >
> > sparc pci_resource_to_user does return BAR value for iomem.

That means it should be implemented using pcibios_resource_to_bus().

> >>   - This implies that pci_mmap_page_range() should deal with resource
> >>     values (CPU physical addresses), and proc_bus_pci_mmap() should do
> >>     any necessary arch-specific translation from BAR values to
> >>     resource values.
> >
> > so will need one different version pci_user_to_resource.
> > and can not use pcibios_bus_to_resource directly, and will be another mess.

What mess do you mean?  The fact that you could only use
pcibios_bus_to_resource() for MEM, and something else for IO?  Even
if we could only use pcibios_bus_to_resource() for MEM, that sounds
like an improvement, not a mess.

> looks like we can avoid that pci_user_to_resource() via trying out.
> Please check it:
> 
> 
> Subject: [RFC PATCH] PCI: Let pci_mmap_page_range() take resource addr
> 
> Some arch where cpu address (resource value) is not same as pci bus address
> (BAR value in pci BAR registers), include sparc, powerpc, microblaze.

This comment is irrelevant.  *Lots* of arches have CPU addresses
different from PCI bus addresses, including alpha, arm, ia64, mips,
mn10300, parisc, tile, xtensa, and x86.

> In 8c05cd08a7 ("PCI: fix offset check for sysfs mmapped files"), try
> to check exposed value with resource start/end in proc mmap path.
> |        start = vma->vm_pgoff;
> |        size = ((pci_resource_len(pdev, resno) - 1) >> PAGE_SHIFT) + 1;
> |        pci_start = (mmap_api == PCI_MMAP_PROCFS) ?
> |                        pci_resource_start(pdev, resno) >> PAGE_SHIFT : 0;
> |        if (start >= pci_start && start < pci_start + size &&
> |                        start + nr <= pci_start + size)
> That would break sparc that exposed value is still BAR value.
> 
> According to Bjorn, we could just pass resource addr instead of BAR.
> 
> In the patch:
> 1. in proc path: proc_bus_pci_mmap, try convert back to resource
>    before calling pci_mmap_page_range
> 2. in sysfs path: pci_mmap_resource will just offset with resource start.
> 3. all pci_mmap_page_range will all have vma->vm_pgoff with in resource range
>    instead of BAR value.
> 
> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
> 
> ---
>  arch/microblaze/pci/pci-common.c |   14 ++++----------
>  arch/powerpc/kernel/pci-common.c |   14 ++++----------
>  arch/sparc/kernel/pci.c          |   27 +++++++++------------------
>  arch/xtensa/kernel/pci.c         |   11 ++++-------
>  drivers/pci/pci-sysfs.c          |    8 +-------
>  drivers/pci/proc.c               |   13 +++++++++++++
>  6 files changed, 35 insertions(+), 52 deletions(-)
> 
> Index: linux-2.6/arch/microblaze/pci/pci-common.c
> ===================================================================
> --- linux-2.6.orig/arch/microblaze/pci/pci-common.c
> +++ linux-2.6/arch/microblaze/pci/pci-common.c
> @@ -169,23 +169,16 @@ static struct resource *__pci_mmap_make_
>                             enum pci_mmap_state mmap_state)
>  {
>      struct pci_controller *hose = pci_bus_to_host(dev->bus);
> -    unsigned long io_offset = 0;
>      int i, res_bit;
> 
>      if (!hose)
>          return NULL;        /* should never happen */
> 
>      /* If memory, add on the PCI bridge address offset */
> -    if (mmap_state == pci_mmap_mem) {
> -#if 0 /* See comment in pci_resource_to_user() for why this is disabled */
> -        *offset += hose->pci_mem_offset;
> -#endif
> +    if (mmap_state == pci_mmap_mem)
>          res_bit = IORESOURCE_MEM;
> -    } else {
> -        io_offset = (unsigned long)hose->io_base_virt - _IO_BASE;
> -        *offset += io_offset;
> +    else
>          res_bit = IORESOURCE_IO;
> -    }
> 
>      /*
>       * Check that the offset requested corresponds to one of the
> @@ -209,7 +202,8 @@ static struct resource *__pci_mmap_make_
> 
>          /* found it! construct the final physical address */
>          if (mmap_state == pci_mmap_io)
> -            *offset += hose->io_base_phys - io_offset;
> +            *offset += hose->io_base_phys -
> +                 ((unsigned long)hose->io_base_virt - _IO_BASE);
>          return rp;
>      }

Most of __pci_mmap_make_offset() is pointless.

We might need something there for I/O regions, but for MEM, the
vma->vm_pgoff coming into pci_mmap_page_range() should be exactly what
we need and we shouldn't touch it.  I think __pci_mmap_make_offset()
actually does leave it alone for MEM, but you have to read the code
carefully to figure that out.

All the validation stuff ("Check that the offset requested corresponds
to one of the resources...") should be removed or moved to
pci_mmap_fits().

> Index: linux-2.6/arch/powerpc/kernel/pci-common.c
> ===================================================================
> --- linux-2.6.orig/arch/powerpc/kernel/pci-common.c
> +++ linux-2.6/arch/powerpc/kernel/pci-common.c
> @@ -308,23 +308,16 @@ static struct resource *__pci_mmap_make_
>                             enum pci_mmap_state mmap_state)
>  {
>      struct pci_controller *hose = pci_bus_to_host(dev->bus);
> -    unsigned long io_offset = 0;
>      int i, res_bit;
> 
>      if (hose == NULL)
>          return NULL;        /* should never happen */
> 
>      /* If memory, add on the PCI bridge address offset */
> -    if (mmap_state == pci_mmap_mem) {
> -#if 0 /* See comment in pci_resource_to_user() for why this is disabled */
> -        *offset += hose->pci_mem_offset;
> -#endif
> +    if (mmap_state == pci_mmap_mem)
>          res_bit = IORESOURCE_MEM;
> -    } else {
> -        io_offset = (unsigned long)hose->io_base_virt - _IO_BASE;
> -        *offset += io_offset;
> +    else
>          res_bit = IORESOURCE_IO;
> -    }
> 
>      /*
>       * Check that the offset requested corresponds to one of the
> @@ -348,7 +341,8 @@ static struct resource *__pci_mmap_make_
> 
>          /* found it! construct the final physical address */
>          if (mmap_state == pci_mmap_io)
> -            *offset += hose->io_base_phys - io_offset;
> +            *offset += hose->io_base_phys -
> +                 ((unsigned long)hose->io_base_virt - _IO_BASE);
>          return rp;
>      }
> 
> Index: linux-2.6/arch/sparc/kernel/pci.c
> ===================================================================
> --- linux-2.6.orig/arch/sparc/kernel/pci.c
> +++ linux-2.6/arch/sparc/kernel/pci.c
> @@ -743,30 +743,21 @@ static int __pci_mmap_make_offset_bus(st
>                        enum pci_mmap_state mmap_state)
>  {
>      struct pci_pbm_info *pbm = pdev->dev.archdata.host_controller;
> -    unsigned long space_size, user_offset, user_size;
> +    unsigned long start, end;
> +    struct resource *res;
> 
> -    if (mmap_state == pci_mmap_io) {
> -        space_size = resource_size(&pbm->io_space);
> -    } else {
> -        space_size = resource_size(&pbm->mem_space);
> -    }
> +    if (mmap_state == pci_mmap_io)
> +        res = &pbm->io_space;
> +    else
> +        res = &pbm->mem_space;
> 
>      /* Make sure the request is in range. */
> -    user_offset = vma->vm_pgoff << PAGE_SHIFT;
> -    user_size = vma->vm_end - vma->vm_start;
> +    start = vma->vm_pgoff << PAGE_SHIFT;
> +    end = vma->vm_end - vma->vm_start + start - 1;
> 
> -    if (user_offset >= space_size ||
> -        (user_offset + user_size) > space_size)
> +    if (!((res->start <= start) && (res->end >= end)))
>          return -EINVAL;
> 
> -    if (mmap_state == pci_mmap_io) {
> -        vma->vm_pgoff = (pbm->io_space.start +
> -                 user_offset) >> PAGE_SHIFT;
> -    } else {
> -        vma->vm_pgoff = (pbm->mem_space.start +
> -                 user_offset) >> PAGE_SHIFT;
> -    }
> -
>      return 0;
>  }
> 
> Index: linux-2.6/arch/xtensa/kernel/pci.c
> ===================================================================
> --- linux-2.6.orig/arch/xtensa/kernel/pci.c
> +++ linux-2.6/arch/xtensa/kernel/pci.c
> @@ -288,20 +288,16 @@ __pci_mmap_make_offset(struct pci_dev *d
>  {
>      struct pci_controller *pci_ctrl = (struct pci_controller*) dev->sysdata;
>      unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;
> -    unsigned long io_offset = 0;
>      int i, res_bit;
> 
>      if (pci_ctrl == 0)
>          return -EINVAL;        /* should never happen */
> 
>      /* If memory, add on the PCI bridge address offset */
> -    if (mmap_state == pci_mmap_mem) {
> +    if (mmap_state == pci_mmap_mem)
>          res_bit = IORESOURCE_MEM;
> -    } else {
> -        io_offset = (unsigned long)pci_ctrl->io_space.base;
> -        offset += io_offset;
> +    else
>          res_bit = IORESOURCE_IO;
> -    }
> 
>      /*
>       * Check that the offset requested corresponds to one of the
> @@ -325,7 +321,8 @@ __pci_mmap_make_offset(struct pci_dev *d
> 
>          /* found it! construct the final physical address */
>          if (mmap_state == pci_mmap_io)
> -            offset += pci_ctrl->io_space.start - io_offset;
> +            offset += pci_ctrl->io_space.start -
> +                    pci_ctrl->io_space.base;
>          vma->vm_pgoff = offset >> PAGE_SHIFT;
>          return 0;
>      }
> Index: linux-2.6/drivers/pci/pci-sysfs.c
> ===================================================================
> --- linux-2.6.orig/drivers/pci/pci-sysfs.c
> +++ linux-2.6/drivers/pci/pci-sysfs.c
> @@ -999,7 +999,6 @@ static int pci_mmap_resource(struct kobj
>      struct pci_dev *pdev = to_pci_dev(kobj_to_dev(kobj));
>      struct resource *res = attr->private;
>      enum pci_mmap_state mmap_type;
> -    resource_size_t start, end;
>      int i;
> 
>      for (i = 0; i < PCI_ROM_RESOURCE; i++)
> @@ -1020,12 +1019,7 @@ static int pci_mmap_resource(struct kobj
>          return -EINVAL;
>      }
> 
> -    /* pci_mmap_page_range() expects the same kind of entry as coming
> -     * from /proc/bus/pci/ which is a "user visible" value. If this is
> -     * different from the resource itself, arch will do necessary fixup.
> -     */
> -    pci_resource_to_user(pdev, i, res, &start, &end);
> -    vma->vm_pgoff += start >> PAGE_SHIFT;
> +    vma->vm_pgoff += res->start >> PAGE_SHIFT;
>      mmap_type = res->flags & IORESOURCE_MEM ? pci_mmap_mem : pci_mmap_io;
>      return pci_mmap_page_range(pdev, vma, mmap_type, write_combine);

This is a definite improvement.  This path doesn't use user addresses,
so getting rid of pci_resource_to_user() here helps a lot.

>  }
> Index: linux-2.6/drivers/pci/proc.c
> ===================================================================
> --- linux-2.6.orig/drivers/pci/proc.c
> +++ linux-2.6/drivers/pci/proc.c
> @@ -231,13 +231,26 @@ static int proc_bus_pci_mmap(struct file
>  {
>      struct pci_dev *dev = PDE_DATA(file_inode(file));
>      struct pci_filp_private *fpriv = file->private_data;
> +    resource_size_t start, end, offset;
> +    struct resource *res;
>      int i, ret;
> 
>      if (!capable(CAP_SYS_RAWIO))
>          return -EPERM;
> 
> +    offset = vma->vm_pgoff << PAGE_SHIFT;
> +
>      /* Make sure the caller is mapping a real resource for this device */
>      for (i = 0; i < PCI_ROM_RESOURCE; i++) {
> +        res = &dev->resource[i];
> +        if (!res->flags)
> +            continue;
> +
> +        pci_resource_to_user(dev, i, res, &start, &end);
> +        if (!(offset >= start && offset <= end))
> +            continue;
> +
> +        vma->vm_pgoff = (res->start + (offset - start)) >> PAGE_SHIFT;
>          if (pci_mmap_fits(dev, i, vma,  PCI_MMAP_PROCFS))

This is sort of OK, but I think we can do better.  I don't see any
problem with introducing pci_user_to_resource() as the inverse of
pci_resource_to_user().  I think it will make this code read much
better.

The default pci_user_to_resource() would do nothing, just like the
default pci_resource_to_user().

For sparc, I think pci_user_to_resource() can use
pcibios_bus_to_resource(), and pci_resource_to_user() can be rewritten
to use pcibios_resource_to_bus().  That makes it much more obvious
what's happening.

It looks like microblaze and powerpc should use
pcibios_resource_to_bus() for I/O resources and the default "user
address == resource address" for MMIO (?)

My goal is to make pci_mmap_resource() and proc_bus_pci_mmap() look
very similar, e.g.,

  /* locate resource */
  pci_user_to_resource()                # only in proc_bus_pci_mmap()
  if (!pci_mmap_fits()) {
    WARN(...);
    return -EINVAL;
  }
  pci_mmap_page_range();

Obviously there are several steps in getting here.  Reworking
pci_resource_to_user() to use pcibios_resource_to_bus() when possible
would be a good start.

Bjorn

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