Re: [PATCH v3 17/26] vfio_pci: Loop using PCI_STD_NUM_BARS

[Andrew Murray]

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@xxxxxxxxxx>
> >> Cc: Alex Williamson <alex.williamson@xxxxxxxxxx>
> >> Signed-off-by: Denis Efremov <efremov@xxxxxxxxx>
> >> ---
> >>  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
> >>
>