Re: [PATCH v3 2/3] vfio/pci: Replace vfio_pci_core_setup_barmap() with vfio_pci_core_get_iomap()

[Alex Williamson <alex@shazbot.org>]

On Thu, 30 Apr 2026 03:03:21 -0700
Matt Evans <mattev@meta.com> wrote:

> Since "vfio/pci: Set up barmap in vfio_pci_core_enable()", the
> resource request and iomap for the BARs was performed early, and
> vfio_pci_core_setup_barmap() just checks those actions succeeded.
> 
> Move this logic to a new helper that checks success and returns the
> iomap address, replacing the various bare vdev->barmap[] lookups.
> This maintains the error behaviour of the previous on-demand
> vfio_pci_core_setup_barmap() scheme.> 
> Signed-off-by: Matt Evans <mattev@meta.com>
> ---
>  drivers/vfio/pci/nvgrace-gpu/main.c | 17 +++++++------
>  drivers/vfio/pci/vfio_pci_core.c    | 11 ++++-----
>  drivers/vfio/pci/vfio_pci_rdwr.c    | 37 +++++++----------------------
>  drivers/vfio/pci/virtio/legacy_io.c | 13 +++++-----
>  include/linux/vfio_pci_core.h       | 19 ++++++++++++++-
>  5 files changed, 47 insertions(+), 50 deletions(-)
> 
> diff --git a/drivers/vfio/pci/nvgrace-gpu/main.c b/drivers/vfio/pci/nvgrace-gpu/main.c
> index fa056b69f899..2f5ec60c15d9 100644
> --- a/drivers/vfio/pci/nvgrace-gpu/main.c
> +++ b/drivers/vfio/pci/nvgrace-gpu/main.c
> @@ -184,13 +184,11 @@ static int nvgrace_gpu_open_device(struct vfio_device *core_vdev)
>  
>  	/*
>  	 * GPU readiness is checked by reading the BAR0 registers.
> -	 *
> -	 * ioremap BAR0 to ensure that the BAR0 mapping is present before
> -	 * register reads on first fault before establishing any GPU
> -	 * memory mapping.
> +	 * The BAR map was just set up by vfio_pci_core_enable() and,
> +	 * although the readiness check checks validity of the BAR0
> +	 * map, assert early that the map was successful:
>  	 */
> -	ret = vfio_pci_core_setup_barmap(vdev, 0);
> -	if (ret)
> +	if (IS_ERR(vfio_pci_core_get_iomap(vdev, 0)))
>  		goto error_exit;
>  
>  	if (nvdev->resmem.memlength) {
> @@ -265,6 +263,7 @@ static int
>  nvgrace_gpu_check_device_ready(struct nvgrace_gpu_pci_core_device *nvdev)
>  {
>  	struct vfio_pci_core_device *vdev = &nvdev->core_device;
> +	void __iomem *io;
>  	int ret;
>  
>  	lockdep_assert_held_read(&vdev->memory_lock);
> @@ -275,7 +274,11 @@ nvgrace_gpu_check_device_ready(struct nvgrace_gpu_pci_core_device *nvdev)
>  	if (!__vfio_pci_memory_enabled(vdev))
>  		return -EIO;
>  
> -	ret = nvgrace_gpu_wait_device_ready(vdev->barmap[0]);
> +	io = vfio_pci_core_get_iomap(vdev, 0);
> +	if (IS_ERR(io))
> +		return PTR_ERR(io);
> +
> +	ret = nvgrace_gpu_wait_device_ready(io);

I suspect the preference would be to test:

	if (IS_ERR(vfio_pci_core_get_iomap(vdev, 0)))
		goto error_exit;

in nvgrace_gpu_open_device(), then just use:

	ret = nvgrace_gpu_wait_device_ready(vfio_pci_core_get_iomap(vdev, 0);

here.


>  	if (ret)
>  		return ret;
>  
> diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
> index eab4f2626b39..feaf894ac118 100644
> --- a/drivers/vfio/pci/vfio_pci_core.c
> +++ b/drivers/vfio/pci/vfio_pci_core.c
> @@ -1760,7 +1760,7 @@ int vfio_pci_core_mmap(struct vfio_device *core_vdev, struct vm_area_struct *vma
>  	struct pci_dev *pdev = vdev->pdev;
>  	unsigned int index;
>  	u64 phys_len, req_len, pgoff, req_start;
> -	int ret;
> +	void __iomem *bar_io;
>  
>  	index = vma->vm_pgoff >> (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT);
>  
> @@ -1794,12 +1794,11 @@ int vfio_pci_core_mmap(struct vfio_device *core_vdev, struct vm_area_struct *vma
>  		return -EINVAL;
>  
>  	/*
> -	 * Even though we don't make use of the barmap for the mmap,
> -	 * we need to request the region and the barmap tracks that.
> +	 * Ensure the BAR resource region is reserved for use.
>  	 */
> -	ret = vfio_pci_core_setup_barmap(vdev, index);
> -	if (ret)
> -		return ret;
> +	bar_io = vfio_pci_core_get_iomap(vdev, index);
> +	if (IS_ERR(bar_io))
> +		return PTR_ERR(bar_io);
>  
>  	vma->vm_private_data = vdev;
>  	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
> diff --git a/drivers/vfio/pci/vfio_pci_rdwr.c b/drivers/vfio/pci/vfio_pci_rdwr.c
> index f66ad3d96481..7f14dd46de17 100644
> --- a/drivers/vfio/pci/vfio_pci_rdwr.c
> +++ b/drivers/vfio/pci/vfio_pci_rdwr.c
> @@ -198,26 +198,6 @@ ssize_t vfio_pci_core_do_io_rw(struct vfio_pci_core_device *vdev, bool test_mem,
>  }
>  EXPORT_SYMBOL_GPL(vfio_pci_core_do_io_rw);
>  
> -int vfio_pci_core_setup_barmap(struct vfio_pci_core_device *vdev, int bar)
> -{
> -	/*
> -	 * The barmap is set up in vfio_pci_core_enable().  Callers
> -	 * use this function to check that the BAR resources are
> -	 * requested or that the pci_iomap() was done.
> -	 */
> -	if (bar < 0 || bar >= PCI_STD_NUM_BARS)
> -		return -EINVAL;
> -
> -	/* Did vfio_pci_core_map_bars() set it up yet? */
> -	if (!vdev->barmap[bar])
> -		return -ENODEV;
> -
> -	if (IS_ERR(vdev->barmap[bar]))
> -		return PTR_ERR(vdev->barmap[bar]);
> -	return 0;
> -}
> -EXPORT_SYMBOL_GPL(vfio_pci_core_setup_barmap);
> -
>  ssize_t vfio_pci_bar_rw(struct vfio_pci_core_device *vdev, char __user *buf,
>  			size_t count, loff_t *ppos, bool iswrite)
>  {
> @@ -269,13 +249,11 @@ ssize_t vfio_pci_bar_rw(struct vfio_pci_core_device *vdev, char __user *buf,
>  		 */
>  		max_width = VFIO_PCI_IO_WIDTH_4;
>  	} else {
> -		int ret = vfio_pci_core_setup_barmap(vdev, bar);
> -		if (ret) {
> -			done = ret;
> +		io = vfio_pci_core_get_iomap(vdev, bar);
> +		if (IS_ERR(io)) {
> +			done = PTR_ERR(io);
>  			goto out;
>  		}
> -
> -		io = vdev->barmap[bar];
>  	}
>  
>  	if (bar == vdev->msix_bar) {
> @@ -430,6 +408,7 @@ int vfio_pci_ioeventfd(struct vfio_pci_core_device *vdev, loff_t offset,
>  	loff_t pos = offset & VFIO_PCI_OFFSET_MASK;
>  	int ret, bar = VFIO_PCI_OFFSET_TO_INDEX(offset);
>  	struct vfio_pci_ioeventfd *ioeventfd;
> +	void __iomem *io;
>  
>  	/* Only support ioeventfds into BARs */
>  	if (bar > VFIO_PCI_BAR5_REGION_INDEX)
> @@ -447,9 +426,9 @@ int vfio_pci_ioeventfd(struct vfio_pci_core_device *vdev, loff_t offset,
>  	if (count == 8)
>  		return -EINVAL;
>  
> -	ret = vfio_pci_core_setup_barmap(vdev, bar);
> -	if (ret)
> -		return ret;
> +	io = vfio_pci_core_get_iomap(vdev, bar);
> +	if (IS_ERR(io))
> +		return PTR_ERR(io);
>  
>  	mutex_lock(&vdev->ioeventfds_lock);
>  
> @@ -486,7 +465,7 @@ int vfio_pci_ioeventfd(struct vfio_pci_core_device *vdev, loff_t offset,
>  	}
>  
>  	ioeventfd->vdev = vdev;
> -	ioeventfd->addr = vdev->barmap[bar] + pos;
> +	ioeventfd->addr = io + pos;
>  	ioeventfd->data = data;
>  	ioeventfd->pos = pos;
>  	ioeventfd->bar = bar;
> diff --git a/drivers/vfio/pci/virtio/legacy_io.c b/drivers/vfio/pci/virtio/legacy_io.c
> index 1ed349a55629..c868b2177310 100644
> --- a/drivers/vfio/pci/virtio/legacy_io.c
> +++ b/drivers/vfio/pci/virtio/legacy_io.c
> @@ -299,19 +299,18 @@ int virtiovf_pci_ioctl_get_region_info(struct vfio_device *core_vdev,
>  static int virtiovf_set_notify_addr(struct virtiovf_pci_core_device *virtvdev)
>  {
>  	struct vfio_pci_core_device *core_device = &virtvdev->core_device;
> -	int ret;
> +	void __iomem *io;
>  
>  	/*
>  	 * Setup the BAR where the 'notify' exists to be used by vfio as well
>  	 * This will let us mmap it only once and use it when needed.
>  	 */
> -	ret = vfio_pci_core_setup_barmap(core_device,
> -					 virtvdev->notify_bar);
> -	if (ret)
> -		return ret;
> +	io = vfio_pci_core_get_iomap(core_device,
> +				     virtvdev->notify_bar);
> +	if (IS_ERR(io))
> +		return PTR_ERR(io);
>  
> -	virtvdev->notify_addr = core_device->barmap[virtvdev->notify_bar] +
> -			virtvdev->notify_offset;
> +	virtvdev->notify_addr = io + virtvdev->notify_offset;
>  	return 0;
>  }
>  
> diff --git a/include/linux/vfio_pci_core.h b/include/linux/vfio_pci_core.h
> index 2ebba746c18f..5598071c5ea3 100644
> --- a/include/linux/vfio_pci_core.h
> +++ b/include/linux/vfio_pci_core.h
> @@ -188,7 +188,6 @@ int vfio_pci_core_match_token_uuid(struct vfio_device *core_vdev,
>  int vfio_pci_core_enable(struct vfio_pci_core_device *vdev);
>  void vfio_pci_core_disable(struct vfio_pci_core_device *vdev);
>  void vfio_pci_core_finish_enable(struct vfio_pci_core_device *vdev);
> -int vfio_pci_core_setup_barmap(struct vfio_pci_core_device *vdev, int bar);
>  pci_ers_result_t vfio_pci_core_aer_err_detected(struct pci_dev *pdev,
>  						pci_channel_state_t state);
>  ssize_t vfio_pci_core_do_io_rw(struct vfio_pci_core_device *vdev, bool test_mem,
> @@ -234,6 +233,24 @@ static inline bool is_aligned_for_order(struct vm_area_struct *vma,
>  			   !IS_ALIGNED(pfn, 1 << order)));
>  }
>  
> +/*
> + * Returns a BAR's iomap base, or an ERR_PTR() if, for example, the
> + * BAR isn't valid, its resource wasn't acquired, or its iomap
> + * failed.
> + */
> +static inline void __iomem __must_check *
> +vfio_pci_core_get_iomap(struct vfio_pci_core_device *vdev, int bar)
> +{
> +	if (bar < 0 || bar >= PCI_STD_NUM_BARS)
> +		return ERR_PTR(-EINVAL);
> +
> +	/* Did vfio_pci_core_map_bars() set it up yet? */
> +	if (!vdev->barmap[bar])
> +		return ERR_PTR(-ENODEV);
> +
> +	return vdev->barmap[bar];
> +}
> +

Regarding the previously exported symbol, if the concern is that it was
a GPL symbol and now it's a static inline, it's not doing anything that
couldn't easily be open coded, so I don't see an issue.  Thanks,

Alex