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Message-ID: <20190918091719.GA9720@e119886-lin.cambridge.arm.com>
Date: Wed, 18 Sep 2019 10:17:20 +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 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?
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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