[PATCH v1 08/13] mshv: accept partial CPU feature banks

[Wei Hu <weh@linux.microsoft.com>]

From: Wei Liu <wei.liu@kernel.org>

Allow userspace to provide fewer than MSHV_NUM_CPU_FEATURES_BANKS banks
for the create-partition v2 ioctl. Preserve the default disabled-feature
mask for omitted banks instead of rejecting the ioctl or overwriting all
banks.

Signed-off-by: Wei Liu <wei.liu@kernel.org>
---
 drivers/hv/mshv_root_main.c | 12 ++----------
 include/uapi/linux/mshv.h   |  3 ++-
 2 files changed, 4 insertions(+), 11 deletions(-)

diff --git a/drivers/hv/mshv_root_main.c b/drivers/hv/mshv_root_main.c
index 11d3c86050b4..729916e1eacf 100644
--- a/drivers/hv/mshv_root_main.c
+++ b/drivers/hv/mshv_root_main.c
@@ -2423,20 +2423,12 @@ static long mshv_ioctl_process_pt_flags(void __user *user_arg, u64 *pt_flags,
 		    args.pt_isolation >= MSHV_PT_ISOLATION_COUNT)
 			return -EINVAL;
 
-		if (args.pt_num_cpu_fbanks != MSHV_NUM_CPU_FEATURES_BANKS ||
+		if (args.pt_num_cpu_fbanks > MSHV_NUM_CPU_FEATURES_BANKS ||
 		    mshv_field_nonzero(args, pt_rsvd) ||
 		    mshv_field_nonzero(args, pt_rsvd1))
 			return -EINVAL;
 
-		/*
-		 * Note this assumes MSHV_NUM_CPU_FEATURES_BANKS will never
-		 * change and equals HV_PARTITION_PROCESSOR_FEATURES_BANKS
-		 * (i.e. 2).
-		 *
-		 * Further banks (index >= 2) will be modifiable as 'early'
-		 * properties via the set partition property hypercall.
-		 */
-		for (i = 0; i < HV_PARTITION_PROCESSOR_FEATURES_BANKS; i++)
+		for (i = 0; i < args.pt_num_cpu_fbanks; i++)
 			disabled_procs->as_uint64[i] = args.pt_cpu_fbanks[i];
 
 #if IS_ENABLED(CONFIG_X86_64)
diff --git a/include/uapi/linux/mshv.h b/include/uapi/linux/mshv.h
index 4e7f3038f0c6..6d6e0fda63bd 100644
--- a/include/uapi/linux/mshv.h
+++ b/include/uapi/linux/mshv.h
@@ -66,7 +66,8 @@ struct mshv_create_partition {
  * This is extended version of the above initial MSHV_CREATE_PARTITION
  * ioctl and allows for following additional parameters:
  *
- * @pt_num_cpu_fbanks: Must be set to MSHV_NUM_CPU_FEATURES_BANKS.
+ * @pt_num_cpu_fbanks: Number of processor feature banks provided. Must not
+ *                     exceed MSHV_NUM_CPU_FEATURES_BANKS.
  * @pt_cpu_fbanks: Disabled processor feature banks array.
  * @pt_disabled_xsave: Disabled xsave feature bits.
  *
-- 
2.43.0