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Date: Thu, 19 Sep 2019 09:00:38 +0100
From: Andrew Murray <andrew.murray@....com>
To: Denis Efremov <efremov@...ux.com>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>, linux-kernel@...r.kernel.org,
linux-pci@...r.kernel.org, kvm@...r.kernel.org,
Cornelia Huck <cohuck@...hat.com>,
Alex Williamson <alex.williamson@...hat.com>
Subject: Re: [PATCH v3 17/26] vfio_pci: Loop using PCI_STD_NUM_BARS
On Wed, Sep 18, 2019 at 05:31:33PM +0300, Denis Efremov wrote:
> On 9/18/19 12:17 PM, Andrew Murray wrote:
> > On Mon, Sep 16, 2019 at 11:41:49PM +0300, Denis Efremov wrote:
> >> Refactor loops to use idiomatic C style and avoid the fencepost error
> >> of using "i < PCI_STD_RESOURCE_END" when "i <= PCI_STD_RESOURCE_END"
> >> is required, e.g., commit 2f686f1d9bee ("PCI: Correct PCI_STD_RESOURCE_END
> >> usage").
> >>
> >> To iterate through all possible BARs, loop conditions changed to the
> >> *number* of BARs "i < PCI_STD_NUM_BARS", instead of the index of the last
> >> valid BAR "i <= PCI_STD_RESOURCE_END".
> >>
> >> Cc: Cornelia Huck <cohuck@...hat.com>
> >> Cc: Alex Williamson <alex.williamson@...hat.com>
> >> Signed-off-by: Denis Efremov <efremov@...ux.com>
> >> ---
> >> drivers/vfio/pci/vfio_pci.c | 11 ++++++----
> >> drivers/vfio/pci/vfio_pci_config.c | 32 +++++++++++++++--------------
> >> drivers/vfio/pci/vfio_pci_private.h | 4 ++--
> >> 3 files changed, 26 insertions(+), 21 deletions(-)
> >>
> >> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
> >> index 703948c9fbe1..cb7d220d3246 100644
> >> --- a/drivers/vfio/pci/vfio_pci.c
> >> +++ b/drivers/vfio/pci/vfio_pci.c
> >> @@ -110,13 +110,15 @@ static inline bool vfio_pci_is_vga(struct pci_dev *pdev)
> >> static void vfio_pci_probe_mmaps(struct vfio_pci_device *vdev)
> >> {
> >> struct resource *res;
> >> - int bar;
> >> + int i;
> >> struct vfio_pci_dummy_resource *dummy_res;
> >>
> >> INIT_LIST_HEAD(&vdev->dummy_resources_list);
> >>
> >> - for (bar = PCI_STD_RESOURCES; bar <= PCI_STD_RESOURCE_END; bar++) {
> >> - res = vdev->pdev->resource + bar;
> >> + for (i = 0; i < PCI_STD_NUM_BARS; i++) {
> >> + int bar = i + PCI_STD_RESOURCES;
> >> +
> >> + res = &vdev->pdev->resource[bar];
> >
> > Why can't we just drop PCI_STD_RESOURCES and replace it was 0. I understand
> > the abstraction here, but we don't do it elsewhere across the kernel. Is this
> > necessary?
>
> There was a discussion about this particular case:
> https://lkml.org/lkml/2019/8/12/999
>
> It was decided to save the original style for vfio drivers.
OK no problem.
Thanks,
Andrew Murray
>
> >
> > Thanks,
> >
> > Andrew Murray
> >
> >>
> >> if (!IS_ENABLED(CONFIG_VFIO_PCI_MMAP))
> >> goto no_mmap;
> >> @@ -399,7 +401,8 @@ static void vfio_pci_disable(struct vfio_pci_device *vdev)
> >>
> >> vfio_config_free(vdev);
> >>
> >> - for (bar = PCI_STD_RESOURCES; bar <= PCI_STD_RESOURCE_END; bar++) {
> >> + for (i = 0; i < PCI_STD_NUM_BARS; i++) {
> >> + bar = i + PCI_STD_RESOURCES;
> >> if (!vdev->barmap[bar])
> >> continue;
> >> pci_iounmap(pdev, vdev->barmap[bar]);
> >> diff --git a/drivers/vfio/pci/vfio_pci_config.c b/drivers/vfio/pci/vfio_pci_config.c
> >> index f0891bd8444c..90c0b80f8acf 100644
> >> --- a/drivers/vfio/pci/vfio_pci_config.c
> >> +++ b/drivers/vfio/pci/vfio_pci_config.c
> >> @@ -450,30 +450,32 @@ static void vfio_bar_fixup(struct vfio_pci_device *vdev)
> >> {
> >> struct pci_dev *pdev = vdev->pdev;
> >> int i;
> >> - __le32 *bar;
> >> + __le32 *vbar;
> >> u64 mask;
> >>
> >> - bar = (__le32 *)&vdev->vconfig[PCI_BASE_ADDRESS_0];
> >> + vbar = (__le32 *)&vdev->vconfig[PCI_BASE_ADDRESS_0];
> >>
> >> - for (i = PCI_STD_RESOURCES; i <= PCI_STD_RESOURCE_END; i++, bar++) {
> >> - if (!pci_resource_start(pdev, i)) {
> >> - *bar = 0; /* Unmapped by host = unimplemented to user */
> >> + for (i = 0; i < PCI_STD_NUM_BARS; i++, vbar++) {
> >> + int bar = i + PCI_STD_RESOURCES;
> >> +
> >> + if (!pci_resource_start(pdev, bar)) {
> >> + *vbar = 0; /* Unmapped by host = unimplemented to user */
> >> continue;
> >> }
> >>
> >> - mask = ~(pci_resource_len(pdev, i) - 1);
> >> + mask = ~(pci_resource_len(pdev, bar) - 1);
> >>
> >> - *bar &= cpu_to_le32((u32)mask);
> >> - *bar |= vfio_generate_bar_flags(pdev, i);
> >> + *vbar &= cpu_to_le32((u32)mask);
> >> + *vbar |= vfio_generate_bar_flags(pdev, bar);
> >>
> >> - if (*bar & cpu_to_le32(PCI_BASE_ADDRESS_MEM_TYPE_64)) {
> >> - bar++;
> >> - *bar &= cpu_to_le32((u32)(mask >> 32));
> >> + if (*vbar & cpu_to_le32(PCI_BASE_ADDRESS_MEM_TYPE_64)) {
> >> + vbar++;
> >> + *vbar &= cpu_to_le32((u32)(mask >> 32));
> >> i++;
> >> }
> >> }
> >>
> >> - bar = (__le32 *)&vdev->vconfig[PCI_ROM_ADDRESS];
> >> + vbar = (__le32 *)&vdev->vconfig[PCI_ROM_ADDRESS];
> >>
> >> /*
> >> * NB. REGION_INFO will have reported zero size if we weren't able
> >> @@ -483,14 +485,14 @@ static void vfio_bar_fixup(struct vfio_pci_device *vdev)
> >> if (pci_resource_start(pdev, PCI_ROM_RESOURCE)) {
> >> mask = ~(pci_resource_len(pdev, PCI_ROM_RESOURCE) - 1);
> >> mask |= PCI_ROM_ADDRESS_ENABLE;
> >> - *bar &= cpu_to_le32((u32)mask);
> >> + *vbar &= cpu_to_le32((u32)mask);
> >> } else if (pdev->resource[PCI_ROM_RESOURCE].flags &
> >> IORESOURCE_ROM_SHADOW) {
> >> mask = ~(0x20000 - 1);
> >> mask |= PCI_ROM_ADDRESS_ENABLE;
> >> - *bar &= cpu_to_le32((u32)mask);
> >> + *vbar &= cpu_to_le32((u32)mask);
> >> } else
> >> - *bar = 0;
> >> + *vbar = 0;
> >>
> >> vdev->bardirty = false;
> >> }
> >> diff --git a/drivers/vfio/pci/vfio_pci_private.h b/drivers/vfio/pci/vfio_pci_private.h
> >> index ee6ee91718a4..8a2c7607d513 100644
> >> --- a/drivers/vfio/pci/vfio_pci_private.h
> >> +++ b/drivers/vfio/pci/vfio_pci_private.h
> >> @@ -86,8 +86,8 @@ struct vfio_pci_reflck {
> >>
> >> struct vfio_pci_device {
> >> struct pci_dev *pdev;
> >> - void __iomem *barmap[PCI_STD_RESOURCE_END + 1];
> >> - bool bar_mmap_supported[PCI_STD_RESOURCE_END + 1];
> >> + void __iomem *barmap[PCI_STD_NUM_BARS];
> >> + bool bar_mmap_supported[PCI_STD_NUM_BARS];
> >> u8 *pci_config_map;
> >> u8 *vconfig;
> >> struct perm_bits *msi_perm;
> >> --
> >> 2.21.0
> >>
>
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