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* [PATCH v2] mshv: Simplify GPA map/unmap hypercall helpers
@ 2026-04-29 16:48 Stanislav Kinsburskii
  2026-04-30  2:06 ` Mukesh R
  0 siblings, 1 reply; 3+ messages in thread
From: Stanislav Kinsburskii @ 2026-04-29 16:48 UTC (permalink / raw)
  To: kys, haiyangz, wei.liu, decui, longli; +Cc: linux-hyperv, linux-kernel

Clean up hv_do_map_gpa_hcall() and hv_call_unmap_gpa_pages() after the
preceding bug-fix patches:

Move "done += completed" before the status checks so that pages mapped
by a partially-successful batch are included in the error cleanup unmap.
Previously these mappings were leaked on failure.

While here, improve type safety and readability:
 - Change "int done" to "u64 done" to match the u64 page_count it is
   compared against, avoiding signed/unsigned comparison hazards.
 - Use u64 for loop iteration and batch size variables consistently.
 - Add proper braces to the for-loop body in hv_do_map_gpa_hcall().
 - Remove unnecessary "ret" variable from hv_call_unmap_gpa_pages().
 - Simplify the error-path unmap to use "done << large_shift" directly
   instead of mutating done in place.

Fixes: 621191d709b14 ("Drivers: hv: Introduce mshv_root module to expose /dev/mshv to VMMs")
Signed-off-by: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
---
 drivers/hv/mshv_root_hv_call.c |   55 +++++++++++++++-------------------------
 1 file changed, 20 insertions(+), 35 deletions(-)

diff --git a/drivers/hv/mshv_root_hv_call.c b/drivers/hv/mshv_root_hv_call.c
index e5992c324904a..1f19a4ca824f0 100644
--- a/drivers/hv/mshv_root_hv_call.c
+++ b/drivers/hv/mshv_root_hv_call.c
@@ -195,8 +195,8 @@ static int hv_do_map_gpa_hcall(u64 partition_id, u64 gfn, u64 page_struct_count,
 	struct hv_input_map_gpa_pages *input_page;
 	u64 status, *pfnlist;
 	unsigned long irq_flags, large_shift = 0;
-	int ret = 0, done = 0;
-	u64 page_count = page_struct_count;
+	u64 done = 0, page_count = page_struct_count;
+	int ret = 0;
 
 	if (page_count == 0 || (pages && mmio_spa))
 		return -EINVAL;
@@ -213,8 +213,8 @@ static int hv_do_map_gpa_hcall(u64 partition_id, u64 gfn, u64 page_struct_count,
 	}
 
 	while (done < page_count) {
-		ulong i, completed, remain = page_count - done;
-		int rep_count = min(remain, HV_MAP_GPA_BATCH_SIZE);
+		u64 i, completed, remain = page_count - done;
+		u64 rep_count = min_t(u64, remain, HV_MAP_GPA_BATCH_SIZE);
 
 		local_irq_save(irq_flags);
 		input_page = *this_cpu_ptr(hyperv_pcpu_input_arg);
@@ -224,23 +224,13 @@ static int hv_do_map_gpa_hcall(u64 partition_id, u64 gfn, u64 page_struct_count,
 		input_page->map_flags = flags;
 		pfnlist = input_page->source_gpa_page_list;
 
-		for (i = 0; i < rep_count; i++)
-			if (flags & HV_MAP_GPA_NO_ACCESS) {
+		for (i = 0; i < rep_count; i++) {
+			if (flags & HV_MAP_GPA_NO_ACCESS)
 				pfnlist[i] = 0;
-			} else if (pages) {
-				u64 index = (done + i) << large_shift;
-
-				if (index >= page_struct_count) {
-					ret = -EINVAL;
-					break;
-				}
-				pfnlist[i] = page_to_pfn(pages[index]);
-			} else {
+			else if (pages)
+				pfnlist[i] = page_to_pfn(pages[(done + i) << large_shift]);
+			else
 				pfnlist[i] = mmio_spa + done + i;
-			}
-		if (ret) {
-			local_irq_restore(irq_flags);
-			break;
 		}
 
 		status = hv_do_rep_hypercall(HVCALL_MAP_GPA_PAGES, rep_count, 0,
@@ -248,29 +238,26 @@ static int hv_do_map_gpa_hcall(u64 partition_id, u64 gfn, u64 page_struct_count,
 		local_irq_restore(irq_flags);
 
 		completed = hv_repcomp(status);
+		done += completed;
 
 		if (hv_result_needs_memory(status)) {
 			ret = hv_call_deposit_pages(NUMA_NO_NODE, partition_id,
 						    HV_MAP_GPA_DEPOSIT_PAGES);
 			if (ret)
 				break;
-
 		} else if (!hv_result_success(status)) {
 			ret = hv_result_to_errno(status);
 			break;
 		}
-
-		done += completed;
 	}
 
 	if (ret && done) {
 		u32 unmap_flags = 0;
 
-		if (flags & HV_MAP_GPA_LARGE_PAGE) {
+		if (flags & HV_MAP_GPA_LARGE_PAGE)
 			unmap_flags |= HV_UNMAP_GPA_LARGE_PAGE;
-			done <<= large_shift;
-		}
-		hv_call_unmap_gpa_pages(partition_id, gfn, done, unmap_flags);
+		hv_call_unmap_gpa_pages(partition_id, gfn,
+					done << large_shift, unmap_flags);
 	}
 
 	return ret;
@@ -305,7 +292,7 @@ int hv_call_unmap_gpa_pages(u64 partition_id, u64 gfn, u64 page_count_4k,
 	struct hv_input_unmap_gpa_pages *input_page;
 	u64 status, page_count = page_count_4k;
 	unsigned long irq_flags, large_shift = 0;
-	int ret = 0, done = 0;
+	u64 done = 0;
 
 	if (page_count == 0)
 		return -EINVAL;
@@ -319,8 +306,8 @@ int hv_call_unmap_gpa_pages(u64 partition_id, u64 gfn, u64 page_count_4k,
 	}
 
 	while (done < page_count) {
-		ulong completed, remain = page_count - done;
-		int rep_count = min(remain, HV_UMAP_GPA_PAGES);
+		u64 completed, remain = page_count - done;
+		u64 rep_count = min_t(u64, remain, HV_UMAP_GPA_PAGES);
 
 		local_irq_save(irq_flags);
 		input_page = *this_cpu_ptr(hyperv_pcpu_input_arg);
@@ -333,15 +320,13 @@ int hv_call_unmap_gpa_pages(u64 partition_id, u64 gfn, u64 page_count_4k,
 		local_irq_restore(irq_flags);
 
 		completed = hv_repcomp(status);
-		if (!hv_result_success(status)) {
-			ret = hv_result_to_errno(status);
-			break;
-		}
-
 		done += completed;
+
+		if (!hv_result_success(status))
+			return hv_result_to_errno(status);
 	}
 
-	return ret;
+	return 0;
 }
 
 int hv_call_get_gpa_access_states(u64 partition_id, u32 count, u64 gpa_base_pfn,



^ permalink raw reply related	[flat|nested] 3+ messages in thread
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2026-04-29 16:48 [PATCH v2] mshv: Simplify GPA map/unmap hypercall helpers Stanislav Kinsburskii
2026-04-30  2:06 ` Mukesh R
2026-04-30 14:43   ` Stanislav Kinsburskii

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