powerpc/powernv: Enable HAIL (HV AIL) for ISA v3.1 processors

Starting with ISA v3.1, LPCR[AIL] no longer controls the interrupt
mode for HV=1 interrupts. Instead, a new LPCR[HAIL] bit is defined
which behaves like AIL=3 for HV interrupts when set.

Set HAIL on bare metal to give us mmu-on interrupts and improve
performance.

This also fixes an scv bug: we don't implement scv real mode (AIL=0)
vectors because they are at an inconvenient location, so we just
disable scv support when AIL can not be set. However powernv assumes
that LPCR[AIL] will enable AIL mode so it enables scv support despite
HV interrupts being AIL=0, which causes scv interrupts to go off into
the weeds.

Fixes: 7fa95f9a ("powerpc/64s: system call support for scv/rfscv instructions")
Cc: stable@vger.kernel.org # v5.9+
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210402024124.545826-1-npiggin@gmail.com

arch/powerpc/include/asm/reg.h

@@ -441,6 +441,7 @@
 #define   LPCR_VRMA_LP1		ASM_CONST(0x0000800000000000)
 #define   LPCR_RMLS		0x1C000000	/* Implementation dependent RMO limit sel */
 #define   LPCR_RMLS_SH		26
+#define   LPCR_HAIL		ASM_CONST(0x0000000004000000)   /* HV AIL (ISAv3.1) */
 #define   LPCR_ILE		ASM_CONST(0x0000000002000000)   /* !HV irqs set MSR:LE */
 #define   LPCR_AIL		ASM_CONST(0x0000000001800000)	/* Alternate interrupt location */
 #define   LPCR_AIL_0		ASM_CONST(0x0000000000000000)	/* MMU off exception offset 0x0 */

arch/powerpc/kernel/setup_64.c

@@ -232,10 +232,23 @@ static void cpu_ready_for_interrupts(void)
 	 * If we are not in hypervisor mode the job is done once for
 	 * the whole partition in configure_exceptions().
 	 */
-	if (cpu_has_feature(CPU_FTR_HVMODE) &&
-	    cpu_has_feature(CPU_FTR_ARCH_207S)) {
+	if (cpu_has_feature(CPU_FTR_HVMODE)) {
 		unsigned long lpcr = mfspr(SPRN_LPCR);
-		mtspr(SPRN_LPCR, lpcr | LPCR_AIL_3);
+		unsigned long new_lpcr = lpcr;
+
+		if (cpu_has_feature(CPU_FTR_ARCH_31)) {
+			/* P10 DD1 does not have HAIL */
+			if (pvr_version_is(PVR_POWER10) &&
+					(mfspr(SPRN_PVR) & 0xf00) == 0x100)
+				new_lpcr |= LPCR_AIL_3;
+			else
+				new_lpcr |= LPCR_HAIL;
+		} else if (cpu_has_feature(CPU_FTR_ARCH_207S)) {
+			new_lpcr |= LPCR_AIL_3;
+		}
+
+		if (new_lpcr != lpcr)
+			mtspr(SPRN_LPCR, new_lpcr);
 	}
 
 	/*