linux-kernel - Re: [PATCH v6 4/4] vfio: convey kvm that the vfio-pci device is wc safe

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Date: Thu, 8 Feb 2024 14:53:45 +0000
From: Catalin Marinas <catalin.marinas@....com>
To: ankita@...dia.com
Cc: jgg@...dia.com, maz@...nel.org, oliver.upton@...ux.dev,
	james.morse@....com, suzuki.poulose@....com, yuzenghui@...wei.com,
	reinette.chatre@...el.com, surenb@...gle.com, stefanha@...hat.com,
	brauner@...nel.org, will@...nel.org, mark.rutland@....com,
	alex.williamson@...hat.com, kevin.tian@...el.com,
	yi.l.liu@...el.com, ardb@...nel.org, akpm@...ux-foundation.org,
	andreyknvl@...il.com, wangjinchao@...sion.com, gshan@...hat.com,
	ricarkol@...gle.com, linux-mm@...ck.org, lpieralisi@...nel.org,
	rananta@...gle.com, ryan.roberts@....com, aniketa@...dia.com,
	cjia@...dia.com, kwankhede@...dia.com, targupta@...dia.com,
	vsethi@...dia.com, acurrid@...dia.com, apopple@...dia.com,
	jhubbard@...dia.com, danw@...dia.com, kvmarm@...ts.linux.dev,
	mochs@...dia.com, zhiw@...dia.com, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	David Hildenbrand <david@...hat.com>
Subject: Re: [PATCH v6 4/4] vfio: convey kvm that the vfio-pci device is wc
 safe

+ David H

On Thu, Feb 08, 2024 at 02:16:52AM +0530, ankita@...dia.com wrote:
> From: Ankit Agrawal <ankita@...dia.com>
> 
> The code to map the MMIO in S2 as NormalNC is enabled when conveyed
> that the device is WC safe using a new flag VM_VFIO_ALLOW_WC.
> 
> Make vfio-pci set the VM_VFIO_ALLOW_WC flag.
> 
> This could be extended to other devices in the future once that
> is deemed safe.
> 
> Signed-off-by: Ankit Agrawal <ankita@...dia.com>
> Suggested-by: Catalin Marinas <catalin.marinas@....com>
> Acked-by: Jason Gunthorpe <jgg@...dia.com>
> ---
>  drivers/vfio/pci/vfio_pci_core.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
> index 1cbc990d42e0..c3f95ec7fc3a 100644
> --- a/drivers/vfio/pci/vfio_pci_core.c
> +++ b/drivers/vfio/pci/vfio_pci_core.c
> @@ -1863,7 +1863,8 @@ int vfio_pci_core_mmap(struct vfio_device *core_vdev, struct vm_area_struct *vma
>  	 * See remap_pfn_range(), called from vfio_pci_fault() but we can't
>  	 * change vm_flags within the fault handler.  Set them now.
>  	 */
> -	vm_flags_set(vma, VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP);
> +	vm_flags_set(vma, VM_VFIO_ALLOW_WC | VM_IO | VM_PFNMAP |
> +			VM_DONTEXPAND | VM_DONTDUMP);
>  	vma->vm_ops = &vfio_pci_mmap_ops;
>  
>  	return 0;

Acked-by: Catalin Marinas <catalin.marinas@....com>