[PATCH 6/6] drm/i915/gvt: use gfn_to_pfn's page instead of pfn

[David Stevens]

Return struct page instead of pfn from gfn_to_mfn. This function is only
used to determine if the page is a transparent hugepage, to enable 2MB
huge gtt shadowing. Returning the page directly avoids the risk of
calling pfn_to_page on a VM_IO|VM_PFNMAP pfn.

This change also properly releases the reference on the page returned by
gfn_to_pfn.

Signed-off-by: David Stevens <stevensd@xxxxxxxxxx>
---
 drivers/gpu/drm/i915/gvt/gtt.c       | 12 ++++++++----
 drivers/gpu/drm/i915/gvt/hypercall.h |  3 ++-
 drivers/gpu/drm/i915/gvt/kvmgt.c     | 12 ++++--------
 drivers/gpu/drm/i915/gvt/mpt.h       |  8 ++++----
 4 files changed, 18 insertions(+), 17 deletions(-)

diff --git a/drivers/gpu/drm/i915/gvt/gtt.c b/drivers/gpu/drm/i915/gvt/gtt.c
index 9478c132d7b6..b2951c560582 100644
--- a/drivers/gpu/drm/i915/gvt/gtt.c
+++ b/drivers/gpu/drm/i915/gvt/gtt.c
@@ -1160,16 +1160,20 @@ static int is_2MB_gtt_possible(struct intel_vgpu *vgpu,
 	struct intel_gvt_gtt_entry *entry)
 {
 	struct intel_gvt_gtt_pte_ops *ops = vgpu->gvt->gtt.pte_ops;
-	unsigned long pfn;
+	struct page *page;
+	bool is_trans_huge;
 
 	if (!HAS_PAGE_SIZES(vgpu->gvt->gt->i915, I915_GTT_PAGE_SIZE_2M))
 		return 0;
 
-	pfn = intel_gvt_hypervisor_gfn_to_mfn(vgpu, ops->get_pfn(entry));
-	if (pfn == INTEL_GVT_INVALID_ADDR)
+	page = intel_gvt_hypervisor_gfn_to_mfn_page(vgpu, ops->get_pfn(entry));
+	if (!page)
 		return -EINVAL;
 
-	return PageTransHuge(pfn_to_page(pfn));
+	is_trans_huge = PageTransHuge(page);
+	put_page(page);
+
+	return is_trans_huge;
 }
 
 static int split_2MB_gtt_entry(struct intel_vgpu *vgpu,
diff --git a/drivers/gpu/drm/i915/gvt/hypercall.h b/drivers/gpu/drm/i915/gvt/hypercall.h
index b79da5124f83..017190ff52d5 100644
--- a/drivers/gpu/drm/i915/gvt/hypercall.h
+++ b/drivers/gpu/drm/i915/gvt/hypercall.h
@@ -60,7 +60,8 @@ struct intel_gvt_mpt {
 			unsigned long len);
 	int (*write_gpa)(unsigned long handle, unsigned long gpa, void *buf,
 			 unsigned long len);
-	unsigned long (*gfn_to_mfn)(unsigned long handle, unsigned long gfn);
+	struct page *(*gfn_to_mfn_page)(unsigned long handle,
+					unsigned long gfn);
 
 	int (*dma_map_guest_page)(unsigned long handle, unsigned long gfn,
 				  unsigned long size, dma_addr_t *dma_addr);
diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
index b829ff67e3d9..1e97ae813ed0 100644
--- a/drivers/gpu/drm/i915/gvt/kvmgt.c
+++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
@@ -1928,21 +1928,17 @@ static int kvmgt_inject_msi(unsigned long handle, u32 addr, u16 data)
 	return -EFAULT;
 }
 
-static unsigned long kvmgt_gfn_to_pfn(unsigned long handle, unsigned long gfn)
+static struct page *kvmgt_gfn_to_page(unsigned long handle, unsigned long gfn)
 {
 	struct kvmgt_guest_info *info;
 	kvm_pfn_t pfn;
 
 	if (!handle_valid(handle))
-		return INTEL_GVT_INVALID_ADDR;
+		return NULL;
 
 	info = (struct kvmgt_guest_info *)handle;
 
-	pfn = kvm_pfn_page_unwrap(gfn_to_pfn(info->kvm, gfn));
-	if (is_error_noslot_pfn(pfn))
-		return INTEL_GVT_INVALID_ADDR;
-
-	return pfn;
+	return gfn_to_pfn(info->kvm, gfn).page;
 }
 
 static int kvmgt_dma_map_guest_page(unsigned long handle, unsigned long gfn,
@@ -2112,7 +2108,7 @@ static const struct intel_gvt_mpt kvmgt_mpt = {
 	.disable_page_track = kvmgt_page_track_remove,
 	.read_gpa = kvmgt_read_gpa,
 	.write_gpa = kvmgt_write_gpa,
-	.gfn_to_mfn = kvmgt_gfn_to_pfn,
+	.gfn_to_mfn_page = kvmgt_gfn_to_page,
 	.dma_map_guest_page = kvmgt_dma_map_guest_page,
 	.dma_unmap_guest_page = kvmgt_dma_unmap_guest_page,
 	.dma_pin_guest_page = kvmgt_dma_pin_guest_page,
diff --git a/drivers/gpu/drm/i915/gvt/mpt.h b/drivers/gpu/drm/i915/gvt/mpt.h
index 550a456e936f..9169b83cf0f6 100644
--- a/drivers/gpu/drm/i915/gvt/mpt.h
+++ b/drivers/gpu/drm/i915/gvt/mpt.h
@@ -214,17 +214,17 @@ static inline int intel_gvt_hypervisor_write_gpa(struct intel_vgpu *vgpu,
 }
 
 /**
- * intel_gvt_hypervisor_gfn_to_mfn - translate a GFN to MFN
+ * intel_gvt_hypervisor_gfn_to_mfn_page - translate a GFN to MFN page
  * @vgpu: a vGPU
  * @gpfn: guest pfn
  *
  * Returns:
- * MFN on success, INTEL_GVT_INVALID_ADDR if failed.
+ * struct page* on success, NULL if failed.
  */
-static inline unsigned long intel_gvt_hypervisor_gfn_to_mfn(
+static inline unsigned long intel_gvt_hypervisor_gfn_to_mfn_page(
 		struct intel_vgpu *vgpu, unsigned long gfn)
 {
-	return intel_gvt_host.mpt->gfn_to_mfn(vgpu->handle, gfn);
+	return intel_gvt_host.mpt->gfn_to_mfn_page(vgpu->handle, gfn);
 }
 
 /**
-- 
2.32.0.93.g670b81a890-goog