linux-kernel - RE: [PATCH v4 1/3] migration: update BAR space size

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Message-ID: <3ec5ffdee2f64c74a82093c06612f59b@huawei.com>
Date: Tue, 24 Jun 2025 07:03:04 +0000
From: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@...wei.com>
To: liulongfang <liulongfang@...wei.com>, "alex.williamson@...hat.com"
	<alex.williamson@...hat.com>, "jgg@...dia.com" <jgg@...dia.com>, "Jonathan
 Cameron" <jonathan.cameron@...wei.com>
CC: "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linuxarm@...neuler.org" <linuxarm@...neuler.org>
Subject: RE: [PATCH v4 1/3] migration: update BAR space size



> -----Original Message-----
> From: liulongfang <liulongfang@...wei.com>
> Sent: Tuesday, June 10, 2025 7:33 AM
> To: alex.williamson@...hat.com; jgg@...dia.com; Shameerali Kolothum
> Thodi <shameerali.kolothum.thodi@...wei.com>; Jonathan Cameron
> <jonathan.cameron@...wei.com>
> Cc: kvm@...r.kernel.org; linux-kernel@...r.kernel.org;
> linuxarm@...neuler.org; liulongfang <liulongfang@...wei.com>
> Subject: [PATCH v4 1/3] migration: update BAR space size
> 
> On the new hardware platform, the live migration configuration region
> is moved from VF to PF. The VF's own configuration space is
> restored to the complete 64KB, and there is no need to divide the
> size of the BAR configuration space equally.
> 
> Signed-off-by: Longfang Liu <liulongfang@...wei.com>
> ---
>  .../vfio/pci/hisilicon/hisi_acc_vfio_pci.c    | 36 ++++++++++++++-----
>  1 file changed, 27 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
> b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
> index 2149f49aeec7..b16115f590fd 100644
> --- a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
> +++ b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
> @@ -1250,6 +1250,28 @@ static struct hisi_qm *hisi_acc_get_pf_qm(struct
> pci_dev *pdev)
>  	return !IS_ERR(pf_qm) ? pf_qm : NULL;
>  }
> 
> +static size_t hisi_acc_get_resource_len(struct vfio_pci_core_device *vdev,
> +					unsigned int index)
> +{
> +	struct hisi_acc_vf_core_device *hisi_acc_vdev =
> +			hisi_acc_drvdata(vdev->pdev);
> +
> +	/*
> +	 * On the old HW_V3 device, the ACC VF device BAR2
> +	 * region encompasses both functional register space
> +	 * and migration control register space.
> +	 * only the functional region should be report to Guest.
> +	 *
> +	 * On the new HW device, the migration control register
> +	 * has been moved to the PF device BAR2 region.
> +	 * The VF device BAR2 is entirely functional register space.
> +	 */
> +	if (hisi_acc_vdev->pf_qm->ver == QM_HW_V3)
> +		return (pci_resource_len(vdev->pdev, index) >> 1);
> +
> +	return pci_resource_len(vdev->pdev, index);
> +}
> +
>  static int hisi_acc_pci_rw_access_check(struct vfio_device *core_vdev,
>  					size_t count, loff_t *ppos,
>  					size_t *new_count)
> @@ -1260,8 +1282,9 @@ static int hisi_acc_pci_rw_access_check(struct
> vfio_device *core_vdev,
> 
>  	if (index == VFIO_PCI_BAR2_REGION_INDEX) {
>  		loff_t pos = *ppos & VFIO_PCI_OFFSET_MASK;
> -		resource_size_t end = pci_resource_len(vdev->pdev, index) /
> 2;
> +		resource_size_t end;
> 
> +		end = hisi_acc_get_resource_len(vdev, index);
>  		/* Check if access is for migration control region */
>  		if (pos >= end)
>  			return -EINVAL;
> @@ -1282,8 +1305,9 @@ static int hisi_acc_vfio_pci_mmap(struct
> vfio_device *core_vdev,
>  	index = vma->vm_pgoff >> (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT);
>  	if (index == VFIO_PCI_BAR2_REGION_INDEX) {
>  		u64 req_len, pgoff, req_start;
> -		resource_size_t end = pci_resource_len(vdev->pdev, index) /
> 2;
> +		resource_size_t end;
> 
> +		end = PAGE_ALIGN(hisi_acc_get_resource_len(vdev, index));

I think I have commented on this before. The above PAGE_ALIGN will change the 
behavior on HW_V3 with 64K PAGE_SIZE kernel. The end will become 64K which
is not what we want on HW_V3. Could you please check that again.

Thanks,
Shameer

>  		req_len = vma->vm_end - vma->vm_start;
>  		pgoff = vma->vm_pgoff &
>  			((1U << (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT)) - 1);
> @@ -1330,7 +1354,6 @@ static long hisi_acc_vfio_pci_ioctl(struct
> vfio_device *core_vdev, unsigned int
>  	if (cmd == VFIO_DEVICE_GET_REGION_INFO) {
>  		struct vfio_pci_core_device *vdev =
>  			container_of(core_vdev, struct vfio_pci_core_device,
> vdev);
> -		struct pci_dev *pdev = vdev->pdev;
>  		struct vfio_region_info info;
>  		unsigned long minsz;
> 
> @@ -1345,12 +1368,7 @@ static long hisi_acc_vfio_pci_ioctl(struct
> vfio_device *core_vdev, unsigned int
>  		if (info.index == VFIO_PCI_BAR2_REGION_INDEX) {
>  			info.offset =
> VFIO_PCI_INDEX_TO_OFFSET(info.index);
> 
> -			/*
> -			 * ACC VF dev BAR2 region consists of both
> functional
> -			 * register space and migration control register
> space.
> -			 * Report only the functional region to Guest.
> -			 */
> -			info.size = pci_resource_len(pdev, info.index) / 2;
> +			info.size = hisi_acc_get_resource_len(vdev,
> info.index);
> 
>  			info.flags = VFIO_REGION_INFO_FLAG_READ |
>  					VFIO_REGION_INFO_FLAG_WRITE |
> --
> 2.24.0