linux-kernel - [PATCH v7 4/4] vfio: convey kvm that the vfio-pci device is wc safe

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Message-ID: <20240211174705.31992-5-ankita@nvidia.com>
Date: Sun, 11 Feb 2024 23:17:05 +0530
From: <ankita@...dia.com>
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Subject: [PATCH v7 4/4] vfio: convey kvm that the vfio-pci device is wc safe

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_ALLOW_ANY_UNCACHED.

Make vfio-pci set the VM_ALLOW_ANY_UNCACHED flag.

This could be extended to other devices in the future once that
is deemed safe.

Suggested-by: Catalin Marinas <catalin.marinas@....com>
Acked-by: Jason Gunthorpe <jgg@...dia.com>
Acked-by: Catalin Marinas <catalin.marinas@....com>
Signed-off-by: Ankit Agrawal <ankita@...dia.com>
---
 drivers/vfio/pci/vfio_pci_core.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
index 1cbc990d42e0..eba2146202f9 100644
--- a/drivers/vfio/pci/vfio_pci_core.c
+++ b/drivers/vfio/pci/vfio_pci_core.c
@@ -1862,8 +1862,12 @@ 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.
+	 *
+	 * Set an additional flag VM_ALLOW_ANY_UNCACHED to convey kvm that
+	 * the device is wc safe.
 	 */
-	vm_flags_set(vma, VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP);
+	vm_flags_set(vma, VM_ALLOW_ANY_UNCACHED | VM_IO | VM_PFNMAP |
+			VM_DONTEXPAND | VM_DONTDUMP);
 	vma->vm_ops = &vfio_pci_mmap_ops;
 
 	return 0;
-- 
2.34.1