On Wed, Jul 01, 2026 at 03:03:35PM +0200, Magnus Kulke wrote:
> Processor features are stored in a union containing two "banks":
>
> union hv_partition_processor_features {
> uint64_t as_uint[2];
> struct {
> uint64_t sse3_support:1;
> ...
> }
> }
>
> get_proc_features() to retrieve the 2nd bank was passing a pointer that
> steps over the whole union (+16B) instead of picking the 2nd bank _in_
> the union. This manifests in mismatching feature bits for the 2nd bank
> and possibly other side-effects caused by writing beyond the union.
>
> We need to step over the first bank (+8B) by using as_uint64[0/1] to
> correct this behaviour.
>
> Fixes: 2f6da91e8a ("accel/mshv: store partition proc features")
> Signed-off-by: Magnus Kulke <[email protected]>
> ---
> accel/mshv/mshv-all.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/accel/mshv/mshv-all.c b/accel/mshv/mshv-all.c
> index 9452504ac2..c8b7f10294 100644
> --- a/accel/mshv/mshv-all.c
> +++ b/accel/mshv/mshv-all.c
> @@ -167,7 +167,7 @@ static int get_proc_features(int vm_fd,
>
> ret = get_partition_property(vm_fd,
> HV_PARTITION_PROPERTY_PROCESSOR_FEATURES0,
> - features[0].as_uint64);
> + &features->as_uint64[0]);
> if (ret < 0) {
> error_report("Failed to get processor features bank 0");
> return -1;
> @@ -175,7 +175,7 @@ static int get_proc_features(int vm_fd,
>
> ret = get_partition_property(vm_fd,
> HV_PARTITION_PROPERTY_PROCESSOR_FEATURES1,
> - features[1].as_uint64);
> + &features->as_uint64[1]);
> if (ret < 0) {
> error_report("Failed to get processor features bank 1");
> return -1;
> --
> 2.34.1
Reviewed-by: Doru Blânzeanu <[email protected]>
