riscv: Add prctl controls for userspace vector management

This patch add two riscv-specific prctls, to allow usespace control the
use of vector unit:

 * PR_RISCV_V_SET_CONTROL: control the permission to use Vector at next,
   or all following execve for a thread. Turning off a thread's Vector
   live is not possible since libraries may have registered ifunc that
   may execute Vector instructions.
 * PR_RISCV_V_GET_CONTROL: get the same permission setting for the
   current thread, and the setting for following execve(s).

Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
Reviewed-by: Greentime Hu <greentime.hu@sifive.com>
Reviewed-by: Vincent Chen <vincent.chen@sifive.com>
Link: https://lore.kernel.org/r/20230605110724.21391-22-andy.chiu@sifive.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
index e5e045852e6a..de24127e7e93 100644
--- a/arch/riscv/kvm/vcpu.c
+++ b/arch/riscv/kvm/vcpu.c
@@ -88,6 +88,8 @@ static bool kvm_riscv_vcpu_isa_enable_allowed(unsigned long ext)
 	switch (ext) {
 	case KVM_RISCV_ISA_EXT_H:
 		return false;
+	case KVM_RISCV_ISA_EXT_V:
+		return riscv_v_vstate_ctrl_user_allowed();
 	default:
 		break;
 	}