arm sve: enable on baremetal by setting missing bits CPACR_EL1.ZEN

README.adoc

@@ -14317,9 +14317,9 @@ ARMv8-only, likely because in ARMv8 you can't have conditional suffixes for ever
 
 ==== ARM bitwise instructions
 
-* link:userland/arch/arm/and.S[]
+* link:userland/arch/arm/and.S[] AND
 * EOR: exclusive OR
-* ORR: OR
+* link:userland/arch/arm/orr.S[]: OR
 * link:userland/arch/arm/clz.S[]: count leading zeroes
 
 ===== ARM BIC instruction
@@ -14741,6 +14741,8 @@ Official spec: https://developer.arm.com/docs/100891/latest/sve-overview/introdu
 
 SVE support is indicated by `ID_AA64PFR0_EL1.SVE` which is dumped from link:baremetal/arch/aarch64/dump_regs.c[].
 
+Using SVE normally requires setting the CPACR_EL1.FPEN and ZEN bits, which as as of lkmc 29fd625f3fda79f5e0ee6cac43517ba74340d513 + 1 we also enable in our <<baremetal-bootloaders>>, see also: <<aarch64-baremetal-neon-setup>>.
+
 ===== SVE bibliography
 
 * https://www.rico.cat/files/ICS18-gem5-sve-tutorial.pdf step by step of a complete code execution examples, the best initial tutorial so far
@@ -15803,15 +15805,17 @@ msr cpacr_el1, x1
 isb
 ....
 
-`cpacr_el1` is documented at <<armarm8>> D10.2.29 "CPACR_EL1, Architectural Feature Access Control Register".
+CPACR_EL1 is documented at <<armarm8>> D10.2.29 "CPACR_EL1, Architectural Feature Access Control Register".
 
-Here we touch the FPEN bits to 3, which enable floating point operations:
+Here we touch the CPACR_EL1.FPEN bits to 3, which enable floating point operations:
 
 ____
 11 This control does not cause any instructions to be trapped.
 ____
 
-Without that, the `printf`:
+We later also added an enable for the CPACR_EL1.ZEN bits, which are needed for <<arm-sve>>.
+
+Without CPACR_EL1.FPEN, the `printf`:
 
 ....
 printf("got: %c\n", c);

baremetal/lib/aarch64.S

@@ -7,7 +7,10 @@ lkmc_start:
     msr vbar_el1, x0
 
     /* https://cirosantilli.com/linux-kernel-module-cheat#aarch64-baremetal-neon-setup */
+    /* CPACR_EL1.FPEN */
     mov x1, 0x3 << 20
+    /* CPACR_EL1.ZEN */
+    orr x1, x1, 0x3 << 16
     msr cpacr_el1, x1
     isb
 

userland/arch/arm/and.S

@@ -4,22 +4,22 @@
 
 LKMC_PROLOGUE
 
-    /* 0x00 && 0xFF == 0x00 */
+    /* 0x00 & 0xFF == 0x00 */
     mov r0, 0x00
     and r0, 0xFF
     LKMC_ASSERT_EQ(r0, =0x00)
 
-    /* 0x0F && 0xF0 == 0x00 */
+    /* 0x0F & 0xF0 == 0x00 */
     mov r0, 0x0F
     and r0, 0xF0
     LKMC_ASSERT_EQ(r0, =0x00)
 
-    /* 0x0F && 0xFF == 0x0F */
+    /* 0x0F & 0xFF == 0x0F */
     mov r0, 0x0F
     and r0, 0xFF
     LKMC_ASSERT_EQ(r0, =0x0F)
 
-    /* 0xF0 && 0xFF == 0xF0 */
+    /* 0xF0 & 0xFF == 0xF0 */
     mov r0, 0xF0
     and r0, 0xFF
     LKMC_ASSERT_EQ(r0, =0xF0)

userland/arch/arm/orr.S

@@ -0,0 +1,27 @@
+/* https://cirosantilli.com/linux-kernel-module-cheat#arm-bitwise-instructions */
+
+#include <lkmc.h>
+
+LKMC_PROLOGUE
+
+    /* 0x00 | 0xFF == 0x00 */
+    mov r0, 0x00
+    orr r0, 0xFF
+    LKMC_ASSERT_EQ(r0, =0xFF)
+
+    /* 0x0F | 0xF0 == 0x00 */
+    mov r0, 0x0F
+    orr r0, 0xF0
+    LKMC_ASSERT_EQ(r0, =0xFF)
+
+    /* 0x0F | 0x0F == 0x0F */
+    mov r0, 0x0F
+    orr r0, 0x0F
+    LKMC_ASSERT_EQ(r0, =0x0F)
+
+    /* 0xF0 | 0xF0 == 0xF0 */
+    mov r0, 0xF0
+    and r0, 0xF0
+    LKMC_ASSERT_EQ(r0, =0xF0)
+
+LKMC_EPILOGUE