Query HV_PARTITION_PROPERTY_PROCESSOR_FEATURES to obtain the feature set
supported by the host and pass on this feature set to the guest during
partition creation.

Signed-off-by: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com>
---
 accel/mshv/mshv-all.c | 47 +++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 45 insertions(+), 2 deletions(-)

diff --git a/accel/mshv/mshv-all.c b/accel/mshv/mshv-all.c
index d4cc7f5371..3b8b9ef116 100644
--- a/accel/mshv/mshv-all.c
+++ b/accel/mshv/mshv-all.c
@@ -110,21 +110,64 @@ static int resume_vm(int vm_fd)
     return 0;
 }
 
+static int get_host_property(int mshv_fd, uint32_t prop_code, uint64_t *value)
+{
+    int ret;
+    struct hv_input_get_partition_property in = {0};
+    struct mshv_root_hvcall args = {0};
+    struct hv_output_get_partition_property out = {0};
+
+    in.property_code = prop_code;
+
+    args.code = HVCALL_GET_PARTITION_PROPERTY;
+    args.in_sz = sizeof(in);
+    args.in_ptr = (uint64_t)&in;
+    args.out_sz = sizeof(out);
+    args.out_ptr = (uint64_t)&out;
+
+    ret = mshv_hvcall(mshv_fd, &args);
+    if (ret < 0) {
+        return -errno;
+    }
+
+    *value = out.property_value;
+    return 0;
+}
+
 static int create_partition(int mshv_fd, int *vm_fd)
 {
     int ret;
-    struct mshv_create_partition args = {0};
+    struct mshv_create_partition_v2 args = {0};
+    uint64_t host_proc_features0, host_proc_features1;
+
+    ret = get_host_property(mshv_fd, HV_PARTITION_PROPERTY_PROCESSOR_FEATURES0,
+                    &host_proc_features0);
+    if (ret < 0) {
+        error_report("Failed to get host processor features (bank 0)");
+        return -1;
+    }
+
+    ret = get_host_property(mshv_fd, HV_PARTITION_PROPERTY_PROCESSOR_FEATURES1,
+                    &host_proc_features1);
+    if (ret < 0) {
+        error_report("Failed to get host processor features (bank 1)");
+        return -1;
+    }
 
     /* Initialize pt_flags with the desired features */
     uint64_t pt_flags = (1ULL << MSHV_PT_BIT_LAPIC) |
                         (1ULL << MSHV_PT_BIT_X2APIC) |
-                        (1ULL << MSHV_PT_BIT_GPA_SUPER_PAGES);
+                        (1ULL << MSHV_PT_BIT_GPA_SUPER_PAGES) |
+                        (1ULL << MSHV_PT_BIT_CPU_AND_XSAVE_FEATURES);
 
     /* Set default isolation type */
     uint64_t pt_isolation = MSHV_PT_ISOLATION_NONE;
 
     args.pt_flags = pt_flags;
     args.pt_isolation = pt_isolation;
+    args.pt_num_cpu_fbanks = MSHV_NUM_CPU_FEATURES_BANKS;
+    args.pt_cpu_fbanks[0] = ~host_proc_features0;
+    args.pt_cpu_fbanks[1] = ~host_proc_features1;
 
     ret = ioctl(mshv_fd, MSHV_CREATE_PARTITION, &args);
     if (ret < 0) {

-- 
2.43.0

On Wed, Mar 11, 2026 at 03:15:28PM +0000, Anirudh Rayabharam (Microsoft) wrote:
> Query HV_PARTITION_PROPERTY_PROCESSOR_FEATURES to obtain the feature set
> supported by the host and pass on this feature set to the guest during
> partition creation.
> 
> Signed-off-by: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com>

I'll drop this patch in v2 in favor of Magnus' patch here:

https://lore.kernel.org/qemu-devel/20260311113505.1177878-2-magnuskulke@linux.microsoft.com/#t

Anirudh.