linux-kernel - [RFC PATCH 11/30] KVM: vfio_dmabuf: Fetch VFIO specific dma-buf data for sanity check

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Message-Id: <20250529053513.1592088-12-yilun.xu@linux.intel.com>
Date: Thu, 29 May 2025 13:34:54 +0800
From: Xu Yilun <yilun.xu@...ux.intel.com>
To: kvm@...r.kernel.org,
	sumit.semwal@...aro.org,
	christian.koenig@....com,
	pbonzini@...hat.com,
	seanjc@...gle.com,
	alex.williamson@...hat.com,
	jgg@...dia.com,
	dan.j.williams@...el.com,
	aik@....com,
	linux-coco@...ts.linux.dev
Cc: dri-devel@...ts.freedesktop.org,
	linux-media@...r.kernel.org,
	linaro-mm-sig@...ts.linaro.org,
	vivek.kasireddy@...el.com,
	yilun.xu@...el.com,
	yilun.xu@...ux.intel.com,
	linux-kernel@...r.kernel.org,
	lukas@...ner.de,
	yan.y.zhao@...el.com,
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Subject: [RFC PATCH 11/30] KVM: vfio_dmabuf: Fetch VFIO specific dma-buf data for sanity check

Fetch VFIO specific dma-buf data to see if the dma-buf is eligible to
be assigned to CoCo VM as private MMIO.

KVM expects host unaccessible MMIO regions been mapped in private
roots. So need to identify VFIO dma-buf by successfully getting VFIO
specific dma-buf data. VFIO dma-buf also provides the struct kvm *kvm
handler for KVM to check if the owner device of the MMIO region is
already assigned to the same CoCo VM.

Signed-off-by: Xu Yilun <yilun.xu@...ux.intel.com>
---
 virt/kvm/vfio_dmabuf.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/virt/kvm/vfio_dmabuf.c b/virt/kvm/vfio_dmabuf.c
index c427ab39c68a..ef695039402f 100644
--- a/virt/kvm/vfio_dmabuf.c
+++ b/virt/kvm/vfio_dmabuf.c
@@ -12,6 +12,22 @@ struct kvm_vfio_dmabuf {
 	struct kvm_memory_slot *slot;
 };
 
+static struct vfio_dma_buf_data *kvm_vfio_dma_buf_get_data(struct dma_buf *dmabuf)
+{
+	struct vfio_dma_buf_data *(*fn)(struct dma_buf *dmabuf);
+	struct vfio_dma_buf_data *ret;
+
+	fn = symbol_get(vfio_dma_buf_get_data);
+	if (!fn)
+		return ERR_PTR(-ENOENT);
+
+	ret = fn(dmabuf);
+
+	symbol_put(vfio_dma_buf_get_data);
+
+	return ret;
+}
+
 static void kv_dmabuf_move_notify(struct dma_buf_attachment *attach)
 {
 	struct kvm_vfio_dmabuf *kv_dmabuf = attach->importer_priv;
@@ -48,6 +64,7 @@ int kvm_vfio_dmabuf_bind(struct kvm *kvm, struct kvm_memory_slot *slot,
 	size_t size = slot->npages << PAGE_SHIFT;
 	struct dma_buf_attachment *attach;
 	struct kvm_vfio_dmabuf *kv_dmabuf;
+	struct vfio_dma_buf_data *data;
 	struct dma_buf *dmabuf;
 	int ret;
 
@@ -60,6 +77,15 @@ int kvm_vfio_dmabuf_bind(struct kvm *kvm, struct kvm_memory_slot *slot,
 		goto err_dmabuf;
 	}
 
+	data = kvm_vfio_dma_buf_get_data(dmabuf);
+	if (IS_ERR(data))
+		goto err_dmabuf;
+
+	if (data->kvm != kvm) {
+		ret = -EINVAL;
+		goto err_dmabuf;
+	}
+
 	kv_dmabuf = kzalloc(sizeof(*kv_dmabuf), GFP_KERNEL);
 	if (!kv_dmabuf) {
 		ret = -ENOMEM;
-- 
2.25.1