[PATCH] mshv: Do not map mmio in map user memory ioctl

[Mukesh R <mrathor@linux.microsoft.com>]

Currently, mshv_map_user_memory() snoops into vma to get the mmio
pfn via vm_pgoff. The mmio pfn is no longer stored there and will
cause the system to crash. Moreover, it is not legit to obtain
mmio pfn via that method. So, remove upfront mmio mappings, just
create region and do basic checks. The mmio entries will be populated
on demand during intercepts in future.

Signed-off-by: Mukesh R <mrathor@linux.microsoft.com>
---
 drivers/hv/mshv_root.h         |  1 -
 drivers/hv/mshv_root_hv_call.c | 15 ---------------
 drivers/hv/mshv_root_main.c    | 28 +++++++++++-----------------
 3 files changed, 11 insertions(+), 33 deletions(-)

diff --git a/drivers/hv/mshv_root.h b/drivers/hv/mshv_root.h
index c61b52db7f00..c0844b28b6a8 100644
--- a/drivers/hv/mshv_root.h
+++ b/drivers/hv/mshv_root.h
@@ -281,7 +281,6 @@ int hv_call_create_partition(u64 flags,
 int hv_call_initialize_partition(u64 partition_id);
 int hv_call_finalize_partition(u64 partition_id);
 int hv_call_delete_partition(u64 partition_id);
-int hv_call_map_mmio_pages(u64 partition_id, u64 gfn, u64 mmio_spa, u64 numpgs);
 int hv_call_map_gpa_pages(u64 partition_id, u64 gpa_target, u64 page_count,
 			  u32 flags, struct page **pages);
 int hv_call_unmap_gpa_pages(u64 partition_id, u64 gpa_target, u64 page_count,
diff --git a/drivers/hv/mshv_root_hv_call.c b/drivers/hv/mshv_root_hv_call.c
index e8485d949951..1287c0a8d118 100644
--- a/drivers/hv/mshv_root_hv_call.c
+++ b/drivers/hv/mshv_root_hv_call.c
@@ -327,21 +327,6 @@ int hv_call_map_gpa_pages(u64 partition_id, u64 gpa_target, u64 page_count,
 				   flags, pages, 0);
 }
 
-/* Ask the hypervisor to map guest mmio space */
-int hv_call_map_mmio_pages(u64 partition_id, u64 gfn, u64 mmio_spa, u64 numpgs)
-{
-	int i;
-	u32 flags = HV_MAP_GPA_READABLE | HV_MAP_GPA_WRITABLE |
-		    HV_MAP_GPA_NOT_CACHED;
-
-	for (i = 0; i < numpgs; i++)
-		if (page_is_ram(mmio_spa + i))
-			return -EINVAL;
-
-	return hv_do_map_gpa_hcall(partition_id, gfn, numpgs, flags, NULL,
-				   mmio_spa);
-}
-
 int hv_call_unmap_gpa_pages(u64 partition_id, u64 gfn, u64 page_count_4k,
 			    u32 flags)
 {
diff --git a/drivers/hv/mshv_root_main.c b/drivers/hv/mshv_root_main.c
index f0bfbbbd7bdd..a11756e5c48d 100644
--- a/drivers/hv/mshv_root_main.c
+++ b/drivers/hv/mshv_root_main.c
@@ -1345,16 +1345,8 @@ static int mshv_prepare_pinned_region(struct mshv_mem_region *region)
 }
 
 /*
- * This maps two things: guest RAM and for pci passthru mmio space.
- *
- * mmio:
- *  - vfio overloads vm_pgoff to store the mmio start pfn/spa.
- *  - Two things need to happen for mapping mmio range:
- *	1. mapped in the uaddr so VMM can access it.
- *	2. mapped in the hwpt (gfn <-> mmio phys addr) so guest can access it.
- *
- *   This function takes care of the second. The first one is managed by vfio,
- *   and hence is taken care of via vfio_pci_mmap_fault().
+ * This is called for both user ram and mmio space. The mmio space is not
+ * mapped here, that should happen later during intercept on demand.
  */
 static long
 mshv_map_user_memory(struct mshv_partition *partition,
@@ -1363,7 +1355,7 @@ mshv_map_user_memory(struct mshv_partition *partition,
 	struct mshv_mem_region *region;
 	struct vm_area_struct *vma;
 	bool is_mmio;
-	ulong mmio_pfn;
+	size_t vma_sz;
 	long ret;
 
 	if (mem->flags & BIT(MSHV_SET_MEM_BIT_UNMAP) ||
@@ -1373,12 +1365,18 @@ mshv_map_user_memory(struct mshv_partition *partition,
 	mmap_read_lock(current->mm);
 	vma = vma_lookup(current->mm, mem->userspace_addr);
 	is_mmio = vma ? !!(vma->vm_flags & (VM_IO | VM_PFNMAP)) : 0;
-	mmio_pfn = is_mmio ? vma->vm_pgoff : 0;
+	if (vma && is_mmio)
+		vma_sz = vma->vm_end - mem->userspace_addr;
 	mmap_read_unlock(current->mm);
 
 	if (!vma)
 		return -EINVAL;
 
+	if (is_mmio)
+		/* Upon mmio intercept, entire region is mapped */
+		if (mem->size > vma_sz)
+			return -EPERM;
+
 	ret = mshv_partition_create_region(partition, mem, &region,
 					   is_mmio);
 	if (ret)
@@ -1399,11 +1397,7 @@ mshv_map_user_memory(struct mshv_partition *partition,
 					    region->nr_pages,
 					    HV_MAP_GPA_NO_ACCESS, NULL);
 		break;
-	case MSHV_REGION_TYPE_MMIO:
-		ret = hv_call_map_mmio_pages(partition->pt_id,
-					     region->start_gfn,
-					     mmio_pfn,
-					     region->nr_pages);
+	default:
 		break;
 	}
 
-- 
2.51.2.vfs.0.1