RE: [PATCH v5 5/7] vfio/nvgrace-gpu: split the code to wait for GPU ready

[Shameer Kolothum]

> -----Original Message-----
> From: Ankit Agrawal <ankita@xxxxxxxxxx>
> Sent: 24 November 2025 11:59
> To: Ankit Agrawal <ankita@xxxxxxxxxx>; jgg@xxxxxxxx; Yishai Hadas
> <yishaih@xxxxxxxxxx>; Shameer Kolothum <skolothumtho@xxxxxxxxxx>;
> kevin.tian@xxxxxxxxx; alex@xxxxxxxxxxx; Aniket Agashe
> <aniketa@xxxxxxxxxx>; Vikram Sethi <vsethi@xxxxxxxxxx>; Matt Ochs
> <mochs@xxxxxxxxxx>
> Cc: Yunxiang.Li@xxxxxxx; yi.l.liu@xxxxxxxxx;
> zhangdongdong@xxxxxxxxxxxxxxxxxx; Avihai Horon <avihaih@xxxxxxxxxx>;
> bhelgaas@xxxxxxxxxx; peterx@xxxxxxxxxx; pstanner@xxxxxxxxxx; Alistair
> Popple <apopple@xxxxxxxxxx>; kvm@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; Neo Jia <cjia@xxxxxxxxxx>; Kirti Wankhede
> <kwankhede@xxxxxxxxxx>; Tarun Gupta (SW-GPU) <targupta@xxxxxxxxxx>;
> Zhi Wang <zhiw@xxxxxxxxxx>; Dan Williams <danw@xxxxxxxxxx>; Dheeraj
> Nigam <dnigam@xxxxxxxxxx>; Krishnakant Jaju <kjaju@xxxxxxxxxx>
> Subject: [PATCH v5 5/7] vfio/nvgrace-gpu: split the code to wait for GPU ready
> 
> 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.
> 
> Signed-off-by: Ankit Agrawal <ankita@xxxxxxxxxx>

Reviewed-by: Shameer Kolothum <skolothumtho@xxxxxxxxxx>

With a nit below:

>  drivers/vfio/pci/nvgrace-gpu/main.c | 33 ++++++++++++++++++-----------
>  1 file changed, 21 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/vfio/pci/nvgrace-gpu/main.c b/drivers/vfio/pci/nvgrace-
> gpu/main.c
> index c84c01954c9e..3e45b8bd1a89 100644
> --- a/drivers/vfio/pci/nvgrace-gpu/main.c
> +++ b/drivers/vfio/pci/nvgrace-gpu/main.c
> @@ -130,6 +130,24 @@ 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);
> +	int ret = -ETIME;
> +
> +	do {
> +		if ((ioread32(io + C2C_LINK_BAR0_OFFSET) ==
> STATUS_READY) &&
> +		    (ioread32(io + HBM_TRAINING_BAR0_OFFSET) ==
> STATUS_READY)) {
> +			ret = 0;
> +			goto ready_check_exit;

You could return directly here and avoid that goto.

Thanks,
Shameer
> +		}
> +		msleep(POLL_QUANTUM_MS);
> +	} while (!time_after(jiffies, timeout));
> +
> +ready_check_exit:
> +	return ret;
> +}
> +
>  static vm_fault_t nvgrace_gpu_vfio_pci_huge_fault(struct vm_fault *vmf,
>  						  unsigned int order)
>  {
> @@ -930,9 +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;
> 
> @@ -950,16 +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);
> @@ -976,7 +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;
> 
> --
> 2.34.1