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target/arm: Handle SVE vector length changes in system mode 

SVE vector length can change when changing EL, or when writing
to one of the ZCR_ELn registers.

For correctness, our implementation requires that predicate bits
that are inaccessible are never set.  Which means noticing length
changes and zeroing the appropriate register bits.

Tested-by: Laurent Desnogues <laurent.desnogues@gmail.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20181005175350.30752-5-richard.henderson@linaro.org
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
master
Richard Henderson 2018-10-08 14:55:02 +01:00 committed by Peter Maydell
parent 2de7ace292
commit 0ab5953b00
4 changed files with 125 additions and 55 deletions
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4
target/arm/cpu.h
View File

@ -910,6 +910,10 @@ int arm_cpu_write_elf32_note(WriteCoreDumpFunction f, CPUState *cs,
int aarch64_cpu_gdb_read_register(CPUState *cpu, uint8_t *buf, int reg);
int aarch64_cpu_gdb_write_register(CPUState *cpu, uint8_t *buf, int reg);
void aarch64_sve_narrow_vq(CPUARMState *env, unsigned vq);
void aarch64_sve_change_el(CPUARMState *env, int old_el, int new_el);
#else
static inline void aarch64_sve_narrow_vq(CPUARMState *env, unsigned vq) { }
static inline void aarch64_sve_change_el(CPUARMState *env, int o, int n) { }
#endif
target_ulong do_arm_semihosting(CPUARMState *env);

42
target/arm/cpu64.c
View File

@ -410,45 +410,3 @@ static void aarch64_cpu_register_types(void)
}
type_init(aarch64_cpu_register_types)
/* The manual says that when SVE is enabled and VQ is widened the
* implementation is allowed to zero the previously inaccessible
* portion of the registers. The corollary to that is that when
* SVE is enabled and VQ is narrowed we are also allowed to zero
* the now inaccessible portion of the registers.
*
* The intent of this is that no predicate bit beyond VQ is ever set.
* Which means that some operations on predicate registers themselves
* may operate on full uint64_t or even unrolled across the maximum
* uint64_t[4]. Performing 4 bits of host arithmetic unconditionally
* may well be cheaper than conditionals to restrict the operation
* to the relevant portion of a uint16_t[16].
*
* TODO: Need to call this for changes to the real system registers
* and EL state changes.
*/
void aarch64_sve_narrow_vq(CPUARMState *env, unsigned vq)
{
int i, j;
uint64_t pmask;
assert(vq >= 1 && vq <= ARM_MAX_VQ);
assert(vq <= arm_env_get_cpu(env)->sve_max_vq);
/* Zap the high bits of the zregs. */
for (i = 0; i < 32; i++) {
memset(&env->vfp.zregs[i].d[2 * vq], 0, 16 * (ARM_MAX_VQ - vq));
}
/* Zap the high bits of the pregs and ffr. */
pmask = 0;
if (vq & 3) {
pmask = ~(-1ULL << (16 * (vq & 3)));
}
for (j = vq / 4; j < ARM_MAX_VQ / 4; j++) {
for (i = 0; i < 17; ++i) {
env->vfp.pregs[i].p[j] &= pmask;
}
pmask = 0;
}
}

133
target/arm/helper.c
View File

@ -4461,11 +4461,44 @@ static int sve_exception_el(CPUARMState *env, int el)
return 0;
}
/*
* Given that SVE is enabled, return the vector length for EL.
*/
static uint32_t sve_zcr_len_for_el(CPUARMState *env, int el)
{
ARMCPU *cpu = arm_env_get_cpu(env);
uint32_t zcr_len = cpu->sve_max_vq - 1;
if (el <= 1) {
zcr_len = MIN(zcr_len, 0xf & (uint32_t)env->vfp.zcr_el[1]);
}
if (el < 2 && arm_feature(env, ARM_FEATURE_EL2)) {
zcr_len = MIN(zcr_len, 0xf & (uint32_t)env->vfp.zcr_el[2]);
}
if (el < 3 && arm_feature(env, ARM_FEATURE_EL3)) {
zcr_len = MIN(zcr_len, 0xf & (uint32_t)env->vfp.zcr_el[3]);
}
return zcr_len;
}
static void zcr_write(CPUARMState *env, const ARMCPRegInfo *ri,
uint64_t value)
{
int cur_el = arm_current_el(env);
int old_len = sve_zcr_len_for_el(env, cur_el);
int new_len;
/* Bits other than [3:0] are RAZ/WI. */
raw_write(env, ri, value & 0xf);
/*
* Because we arrived here, we know both FP and SVE are enabled;
* otherwise we would have trapped access to the ZCR_ELn register.
*/
new_len = sve_zcr_len_for_el(env, cur_el);
if (new_len < old_len) {
aarch64_sve_narrow_vq(env, new_len + 1);
}
}
static const ARMCPRegInfo zcr_el1_reginfo = {
@ -8304,8 +8337,11 @@ static void arm_cpu_do_interrupt_aarch64(CPUState *cs)
unsigned int new_el = env->exception.target_el;
target_ulong addr = env->cp15.vbar_el[new_el];
unsigned int new_mode = aarch64_pstate_mode(new_el, true);
unsigned int cur_el = arm_current_el(env);
if (arm_current_el(env) < new_el) {
aarch64_sve_change_el(env, cur_el, new_el);
if (cur_el < new_el) {
/* Entry vector offset depends on whether the implemented EL
* immediately lower than the target level is using AArch32 or AArch64
*/
@ -12597,18 +12633,7 @@ void cpu_get_tb_cpu_state(CPUARMState *env, target_ulong *pc,
if (sve_el != 0 && fp_el == 0) {
zcr_len = 0;
} else {
ARMCPU *cpu = arm_env_get_cpu(env);
zcr_len = cpu->sve_max_vq - 1;
if (current_el <= 1) {
zcr_len = MIN(zcr_len, 0xf & (uint32_t)env->vfp.zcr_el[1]);
}
if (current_el < 2 && arm_feature(env, ARM_FEATURE_EL2)) {
zcr_len = MIN(zcr_len, 0xf & (uint32_t)env->vfp.zcr_el[2]);
}
if (current_el < 3 && arm_feature(env, ARM_FEATURE_EL3)) {
zcr_len = MIN(zcr_len, 0xf & (uint32_t)env->vfp.zcr_el[3]);
}
zcr_len = sve_zcr_len_for_el(env, current_el);
}
flags |= sve_el << ARM_TBFLAG_SVEEXC_EL_SHIFT;
flags |= zcr_len << ARM_TBFLAG_ZCR_LEN_SHIFT;
@ -12664,3 +12689,85 @@ void cpu_get_tb_cpu_state(CPUARMState *env, target_ulong *pc,
*pflags = flags;
*cs_base = 0;
}
#ifdef TARGET_AARCH64
/*
* The manual says that when SVE is enabled and VQ is widened the
* implementation is allowed to zero the previously inaccessible
* portion of the registers. The corollary to that is that when
* SVE is enabled and VQ is narrowed we are also allowed to zero
* the now inaccessible portion of the registers.
*
* The intent of this is that no predicate bit beyond VQ is ever set.
* Which means that some operations on predicate registers themselves
* may operate on full uint64_t or even unrolled across the maximum
* uint64_t[4]. Performing 4 bits of host arithmetic unconditionally
* may well be cheaper than conditionals to restrict the operation
* to the relevant portion of a uint16_t[16].
*/
void aarch64_sve_narrow_vq(CPUARMState *env, unsigned vq)
{
int i, j;
uint64_t pmask;
assert(vq >= 1 && vq <= ARM_MAX_VQ);
assert(vq <= arm_env_get_cpu(env)->sve_max_vq);
/* Zap the high bits of the zregs. */
for (i = 0; i < 32; i++) {
memset(&env->vfp.zregs[i].d[2 * vq], 0, 16 * (ARM_MAX_VQ - vq));
}
/* Zap the high bits of the pregs and ffr. */
pmask = 0;
if (vq & 3) {
pmask = ~(-1ULL << (16 * (vq & 3)));
}
for (j = vq / 4; j < ARM_MAX_VQ / 4; j++) {
for (i = 0; i < 17; ++i) {
env->vfp.pregs[i].p[j] &= pmask;
}
pmask = 0;
}
}
/*
* Notice a change in SVE vector size when changing EL.
*/
void aarch64_sve_change_el(CPUARMState *env, int old_el, int new_el)
{
int old_len, new_len;
/* Nothing to do if no SVE. */
if (!arm_feature(env, ARM_FEATURE_SVE)) {
return;
}
/* Nothing to do if FP is disabled in either EL. */
if (fp_exception_el(env, old_el) || fp_exception_el(env, new_el)) {
return;
}
/*
* DDI0584A.d sec 3.2: "If SVE instructions are disabled or trapped
* at ELx, or not available because the EL is in AArch32 state, then
* for all purposes other than a direct read, the ZCR_ELx.LEN field
* has an effective value of 0".
*
* Consider EL2 (aa64, vq=4) -> EL0 (aa32) -> EL1 (aa64, vq=0).
* If we ignore aa32 state, we would fail to see the vq4->vq0 transition
* from EL2->EL1. Thus we go ahead and narrow when entering aa32 so that
* we already have the correct register contents when encountering the
* vq0->vq0 transition between EL0->EL1.
*/
old_len = (arm_el_is_aa64(env, old_el) && !sve_exception_el(env, old_el)
? sve_zcr_len_for_el(env, old_el) : 0);
new_len = (arm_el_is_aa64(env, new_el) && !sve_exception_el(env, new_el)
? sve_zcr_len_for_el(env, new_el) : 0);
/* When changing vector length, clear inaccessible state. */
if (new_len < old_len) {
aarch64_sve_narrow_vq(env, new_len + 1);
}
}
#endif

1
target/arm/op_helper.c
View File

@ -1082,6 +1082,7 @@ void HELPER(exception_return)(CPUARMState *env)
"AArch64 EL%d PC 0x%" PRIx64 "\n",
cur_el, new_el, env->pc);
}
aarch64_sve_change_el(env, cur_el, new_el);
qemu_mutex_lock_iothread();
arm_call_el_change_hook(arm_env_get_cpu(env));