[PATCH RFC v3 64/88] vfio: Add vfio_device_gmem_revoke helper for guest_memfd

[Ackerley Tng via B4 Relay]

From: Ackerley Tng <ackerleytng@xxxxxxxxxx>

When physical device regions backing guest_memfd memory must be revoked
due to hardware reset, power state transitions, or memory decode state
changes, the bus driver must revoke and reclaim the memory ranges from
guest_memfd before modifying hardware state.

Add a vfio_device_gmem_revoke() helper in VFIO core that queries whether
the device is attached to a guest_memfd instance and invokes
kvm_gmem_revoke() with the specified range and physical frame address.

Signed-off-by: Ackerley Tng <ackerleytng@xxxxxxxxxx>
---
 drivers/vfio/vfio_main.c | 10 ++++++++++
 include/linux/vfio.h     | 12 ++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
index e4e7bfe77d03b..fd5f71dfc44b7 100644
--- a/drivers/vfio/vfio_main.c
+++ b/drivers/vfio/vfio_main.c
@@ -1643,6 +1643,16 @@ static const struct guest_memfd_provider_operations vfio_device_gmem_provider_op
 	.mmap                 = vfio_device_gmem_mmap,
 	.check_set_attributes = vfio_device_gmem_check_set_attributes,
 };
+
+int vfio_device_gmem_revoke(struct vfio_device *device, pgoff_t start,
+			    size_t nr_pages, const unsigned long *pfn)
+{
+	if (!device->gmem_inode)
+		return 0;
+
+	return kvm_gmem_revoke(device->gmem_inode, start, nr_pages, pfn);
+}
+EXPORT_SYMBOL_GPL(vfio_device_gmem_revoke);
 #endif
 
 const struct file_operations vfio_device_fops = {
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index ffb01e655735f..aade091a91fe8 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -394,6 +394,18 @@ bool vfio_file_is_valid(struct file *file);
 bool vfio_file_enforced_coherent(struct file *file);
 void vfio_file_set_kvm(struct file *vfio_file, struct file *kvm);
 
+#ifdef CONFIG_KVM_GUEST_MEMFD
+int vfio_device_gmem_revoke(struct vfio_device *device, pgoff_t start,
+			    size_t nr_pages, const unsigned long *pfn);
+#else
+static inline int vfio_device_gmem_revoke(struct vfio_device *device,
+					  pgoff_t start, size_t nr_pages,
+					  const unsigned long *pfn)
+{
+	return -EOPNOTSUPP;
+}
+#endif
+
 #define VFIO_PIN_PAGES_MAX_ENTRIES	(PAGE_SIZE/sizeof(unsigned long))
 
 int vfio_pin_pages(struct vfio_device *device, dma_addr_t iova,

-- 
2.56.0.455.g6c5a503b38-goog