linux-kernel - RE: [PATCH v5 2/7] vfio: export function to map the VMA

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Message-ID:
 <CH3PR12MB7548B4BC5D096DB3206A3F05ABD0A@CH3PR12MB7548.namprd12.prod.outlook.com>
Date: Mon, 24 Nov 2025 17:22:20 +0000
From: Shameer Kolothum <skolothumtho@...dia.com>
To: Ankit Agrawal <ankita@...dia.com>, "jgg@...pe.ca" <jgg@...pe.ca>, Yishai
 Hadas <yishaih@...dia.com>, "kevin.tian@...el.com" <kevin.tian@...el.com>,
	"alex@...zbot.org" <alex@...zbot.org>, Aniket Agashe <aniketa@...dia.com>,
	Vikram Sethi <vsethi@...dia.com>, Matt Ochs <mochs@...dia.com>
CC: "Yunxiang.Li@....com" <Yunxiang.Li@....com>, "yi.l.liu@...el.com"
	<yi.l.liu@...el.com>, "zhangdongdong@...incomputing.com"
	<zhangdongdong@...incomputing.com>, Avihai Horon <avihaih@...dia.com>,
	"bhelgaas@...gle.com" <bhelgaas@...gle.com>, "peterx@...hat.com"
	<peterx@...hat.com>, "pstanner@...hat.com" <pstanner@...hat.com>, Alistair
 Popple <apopple@...dia.com>, "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Neo Jia
	<cjia@...dia.com>, Kirti Wankhede <kwankhede@...dia.com>, "Tarun Gupta
 (SW-GPU)" <targupta@...dia.com>, Zhi Wang <zhiw@...dia.com>, Dan Williams
	<danw@...dia.com>, Dheeraj Nigam <dnigam@...dia.com>, Krishnakant Jaju
	<kjaju@...dia.com>
Subject: RE: [PATCH v5 2/7] vfio: export function to map the VMA



> -----Original Message-----
> From: Ankit Agrawal <ankita@...dia.com>
> Sent: 24 November 2025 11:59
> To: Ankit Agrawal <ankita@...dia.com>; jgg@...pe.ca; Yishai Hadas
> <yishaih@...dia.com>; Shameer Kolothum <skolothumtho@...dia.com>;
> kevin.tian@...el.com; alex@...zbot.org; Aniket Agashe
> <aniketa@...dia.com>; Vikram Sethi <vsethi@...dia.com>; Matt Ochs
> <mochs@...dia.com>
> Cc: Yunxiang.Li@....com; yi.l.liu@...el.com;
> zhangdongdong@...incomputing.com; Avihai Horon <avihaih@...dia.com>;
> bhelgaas@...gle.com; peterx@...hat.com; pstanner@...hat.com; Alistair
> Popple <apopple@...dia.com>; kvm@...r.kernel.org; linux-
> kernel@...r.kernel.org; Neo Jia <cjia@...dia.com>; Kirti Wankhede
> <kwankhede@...dia.com>; Tarun Gupta (SW-GPU) <targupta@...dia.com>;
> Zhi Wang <zhiw@...dia.com>; Dan Williams <danw@...dia.com>; Dheeraj
> Nigam <dnigam@...dia.com>; Krishnakant Jaju <kjaju@...dia.com>
> Subject: [PATCH v5 2/7] vfio: export function to map the VMA
> 
> From: Ankit Agrawal <ankita@...dia.com>
> 
> Take out the implementation to map the VMA to the PTE/PMD/PUD
> as a separate function.
> 
> Export the function to be used by nvgrace-gpu module.
> 
> Signed-off-by: Ankit Agrawal <ankita@...dia.com>
> ---
>  drivers/vfio/pci/vfio_pci_core.c | 46 ++++++++++++++++++++------------
>  include/linux/vfio_pci_core.h    |  2 ++
>  2 files changed, 31 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
> index 7dcf5439dedc..ede410e0ae1c 100644
> --- a/drivers/vfio/pci/vfio_pci_core.c
> +++ b/drivers/vfio/pci/vfio_pci_core.c
> @@ -1640,6 +1640,34 @@ static unsigned long vma_to_pfn(struct
> vm_area_struct *vma)
>  	return (pci_resource_start(vdev->pdev, index) >> PAGE_SHIFT) +
> pgoff;
>  }
> +vm_fault_t vfio_pci_vmf_insert_pfn(struct vm_fault *vmf,
> +				   unsigned long pfn,
> +				   unsigned int order)

Does this need to be called with vdev->memory_lock  held?
Please add a comment if so.

> +{
> +	vm_fault_t ret;
> +
> +	switch (order) {
> +	case 0:
> +		ret = vmf_insert_pfn(vmf->vma, vmf->address, pfn);
> +		break;
> +#ifdef CONFIG_ARCH_SUPPORTS_PMD_PFNMAP
> +	case PMD_ORDER:
> +		ret = vmf_insert_pfn_pmd(vmf, pfn, false);
> +		break;
> +#endif
> +#ifdef CONFIG_ARCH_SUPPORTS_PUD_PFNMAP
> +	case PUD_ORDER:
> +		ret = vmf_insert_pfn_pud(vmf, pfn, false);
> +		break;
> +#endif
> +	default:
> +		ret = VM_FAULT_FALLBACK;
> +	}
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(vfio_pci_vmf_insert_pfn);
> +
>  static vm_fault_t vfio_pci_mmap_huge_fault(struct vm_fault *vmf,
>  					   unsigned int order)
>  {
> @@ -1662,23 +1690,7 @@ static vm_fault_t
> vfio_pci_mmap_huge_fault(struct vm_fault *vmf,
>  	if (vdev->pm_runtime_engaged ||
> !__vfio_pci_memory_enabled(vdev))
>  		goto out_unlock;

Is the above check not required for the common helper?

> 
> -	switch (order) {
> -	case 0:
> -		ret = vmf_insert_pfn(vma, vmf->address, pfn);
> -		break;
> -#ifdef CONFIG_ARCH_SUPPORTS_PMD_PFNMAP
> -	case PMD_ORDER:
> -		ret = vmf_insert_pfn_pmd(vmf, pfn, false);
> -		break;
> -#endif
> -#ifdef CONFIG_ARCH_SUPPORTS_PUD_PFNMAP
> -	case PUD_ORDER:
> -		ret = vmf_insert_pfn_pud(vmf, pfn, false);
> -		break;
> -#endif
> -	default:
> -		ret = VM_FAULT_FALLBACK;
> -	}
> +	ret = vfio_pci_vmf_insert_pfn(vmf, pfn, order);
> 
>  out_unlock:
>  	up_read(&vdev->memory_lock);
> diff --git a/include/linux/vfio_pci_core.h b/include/linux/vfio_pci_core.h
> index f541044e42a2..970b3775505e 100644
> --- a/include/linux/vfio_pci_core.h
> +++ b/include/linux/vfio_pci_core.h
> @@ -119,6 +119,8 @@ ssize_t vfio_pci_core_read(struct vfio_device
> *core_vdev, char __user *buf,
>  		size_t count, loff_t *ppos);
>  ssize_t vfio_pci_core_write(struct vfio_device *core_vdev, const char __user
> *buf,
>  		size_t count, loff_t *ppos);
> +vm_fault_t vfio_pci_vmf_insert_pfn(struct vm_fault *vmf, unsigned long pfn,
> +				   unsigned int order);
>  int vfio_pci_core_mmap(struct vfio_device *core_vdev, struct vm_area_struct
> *vma);
>  void vfio_pci_core_request(struct vfio_device *core_vdev, unsigned int
> count);
>  int vfio_pci_core_match(struct vfio_device *core_vdev, char *buf);

Otherwise LGTM:
Reviewed-by: Shameer Kolothum <skolothumtho@...dia.com>