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Date: Wed, 18 Sep 2019 17:31:33 +0300
From: Denis Efremov <efremov@...ux.com>
To: Andrew Murray <andrew.murray@....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 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.
>
> 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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