riscv: Add macro for hfence.gvma instruction

Add an inline function hfence_gvma() for hfence.gvma instruction.

Signed-off-by:	Doongar Singh <doonbsd@gmail.com>
Reviewed by:	mhorne, markj
Differential Revision:	https://reviews.freebsd.org/D54857

sys/riscv/include/cpufunc.h

@@ -119,6 +119,13 @@ sfence_vma_asid_page(uint64_t asid, uintptr_t addr)
 	    : "memory");
 }
 
+static __inline void
+hfence_gvma(void)
+{
+
+	__asm __volatile("hfence.gvma" ::: "memory");
+}
+
 #define	rdcycle()			csr_read64(cycle)
 #define	rdtime()			csr_read64(time)
 #define	rdinstret()			csr_read64(instret)

sys/riscv/vmm/vmm_riscv.c

@@ -625,7 +625,7 @@ vmmops_run(void *vcpui, register_t pc, pmap_t pmap, struct vm_eventinfo *evinfo)
 	 * have been modified, it may be necessary to execute an HFENCE.GVMA
 	 * instruction (see Section 5.3.2) before or after writing hgatp.
 	 */
-	__asm __volatile("hfence.gvma" ::: "memory");
+	hfence_gvma();
 
 	csr_write(hgatp, pmap->pm_satp);
 	if (has_sstc)