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

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Date: Thu, 8 Feb 2024 02:16:52 +0530
From: <ankita@...dia.com>
To: <ankita@...dia.com>, <jgg@...dia.com>, <maz@...nel.org>,
	<oliver.upton@...ux.dev>, <james.morse@....com>, <suzuki.poulose@....com>,
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	<stefanha@...hat.com>, <brauner@...nel.org>, <catalin.marinas@....com>,
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CC: <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>
Subject: [PATCH v6 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_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;
-- 
2.34.1