Re: [PATCH v7 4/6] vfio/nvgrace-gpu: split the code to wait for GPU ready

[Alex Williamson]

On Wed, 26 Nov 2025 05:26:25 +0000
<ankita@xxxxxxxxxx> wrote:

> From: Ankit Agrawal <ankita@xxxxxxxxxx>
> 
> Split the function that check for the GPU device being ready on
> the probe.
> 
> Move the code to wait for the GPU to be ready through BAR0 register
> reads to a separate function. This would help reuse the code.
> 
> This also fixes a bug where the return status in case of timeout
> gets overridden by return from pci_enable_device. With the fix,
> a timeout generate an error as initially intended.
> 
> Fixes: d85f69d520e6 ("vfio/nvgrace-gpu: Check the HBM training and C2C link status")
> 
> Reviewed-by: Zhi Wang <zhiw@xxxxxxxxxx>
> Reviewed-by: Shameer Kolothum <skolothumtho@xxxxxxxxxx>
> Signed-off-by: Ankit Agrawal <ankita@xxxxxxxxxx>
> ---
>  drivers/vfio/pci/nvgrace-gpu/main.c | 29 +++++++++++++++++------------
>  1 file changed, 17 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/vfio/pci/nvgrace-gpu/main.c b/drivers/vfio/pci/nvgrace-gpu/main.c
> index ac9551b9e4b6..f691deb8e43c 100644
> --- a/drivers/vfio/pci/nvgrace-gpu/main.c
> +++ b/drivers/vfio/pci/nvgrace-gpu/main.c
> @@ -130,6 +130,20 @@ static void nvgrace_gpu_close_device(struct vfio_device *core_vdev)
>  	vfio_pci_core_close_device(core_vdev);
>  }
>  
> +static int nvgrace_gpu_wait_device_ready(void __iomem *io)
> +{
> +	unsigned long timeout = jiffies + msecs_to_jiffies(POLL_TIMEOUT_MS);
> +
> +	do {
> +		if ((ioread32(io + C2C_LINK_BAR0_OFFSET) == STATUS_READY) &&
> +		    (ioread32(io + HBM_TRAINING_BAR0_OFFSET) == STATUS_READY))
> +			return 0;
> +		msleep(POLL_QUANTUM_MS);
> +	} while (!time_after(jiffies, timeout));
> +
> +	return -ETIME;
> +}
> +
>  static unsigned long addr_to_pgoff(struct vm_area_struct *vma,
>  				   unsigned long addr)
>  {
> @@ -934,9 +948,8 @@ static bool nvgrace_gpu_has_mig_hw_bug(struct pci_dev *pdev)
>   * Ensure that the BAR0 region is enabled before accessing the
>   * registers.
>   */
> -static int nvgrace_gpu_wait_device_ready(struct pci_dev *pdev)
> +static int nvgrace_gpu_probe_check_device_ready(struct pci_dev *pdev)
>  {
> -	unsigned long timeout = jiffies + msecs_to_jiffies(POLL_TIMEOUT_MS);
>  	void __iomem *io;
>  	int ret = -ETIME;

ret initialization is not needed, it's immediately clobbered.  Thanks,

Alex


>  
> @@ -954,16 +967,8 @@ static int nvgrace_gpu_wait_device_ready(struct pci_dev *pdev)
>  		goto iomap_exit;
>  	}
>  
> -	do {
> -		if ((ioread32(io + C2C_LINK_BAR0_OFFSET) == STATUS_READY) &&
> -		    (ioread32(io + HBM_TRAINING_BAR0_OFFSET) == STATUS_READY)) {
> -			ret = 0;
> -			goto reg_check_exit;
> -		}
> -		msleep(POLL_QUANTUM_MS);
> -	} while (!time_after(jiffies, timeout));
> +	ret = nvgrace_gpu_wait_device_ready(io);
>  
> -reg_check_exit:
>  	pci_iounmap(pdev, io);
>  iomap_exit:
>  	pci_release_selected_regions(pdev, 1 << 0);
> @@ -980,7 +985,7 @@ static int nvgrace_gpu_probe(struct pci_dev *pdev,
>  	u64 memphys, memlength;
>  	int ret;
>  
> -	ret = nvgrace_gpu_wait_device_ready(pdev);
> +	ret = nvgrace_gpu_probe_check_device_ready(pdev);
>  	if (ret)
>  		return ret;
>