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target/arm: Activate M-profile floating point context when FPCCR.ASPEN is set

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The M-profile FPCCR.ASPEN bit indicates that automatic floating-point
context preservation is enabled. Before executing any floating-point
instruction, if FPCCR.ASPEN is set and the CONTROL FPCA/SFPA bits
indicate that there is no active floating point context then we
must create a new context (by initializing FPSCR and setting
FPCA/SFPA to indicate that the context is now active). In the
pseudocode this is handled by ExecuteFPCheck().

Implement this with a new TB flag which tracks whether we
need to create a new FP context.

Backports commit 6000531e19964756673a5f4b694a649ef883605a from qemu
This commit is contained in:
Peter Maydell 2019-04-30 10:51:27 -04:00 committed by Lioncash
parent 87c8c0fde7
commit 719231b4c0
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GPG key ID: 4E3C3CC1031BA9C7
4 changed files with 43 additions and 0 deletions
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2
qemu/target/arm/cpu.h
View file

@ -3110,6 +3110,8 @@ FIELD(TBFLAG_A32, NS, 6, 1)
FIELD(TBFLAG_A32, VFPEN, 7, 1)
FIELD(TBFLAG_A32, CONDEXEC, 8, 8)
FIELD(TBFLAG_A32, SCTLR_B, 16, 1)
/* For M profile only, set if we must create a new FP context */
FIELD(TBFLAG_A32, NEW_FP_CTXT_NEEDED, 19, 1)
/* For M profile only, set if FPCCR.S does not match current security state */
FIELD(TBFLAG_A32, FPCCR_S_WRONG, 20, 1)
/* For M profile only, Handler (ie not Thread) mode */

13
qemu/target/arm/helper.c
View file

@ -13218,6 +13218,19 @@ void cpu_get_tb_cpu_state(CPUARMState *env, target_ulong *pc,
flags = FIELD_DP32(flags, TBFLAG_A32, FPCCR_S_WRONG, 1);
}
if (arm_feature(env, ARM_FEATURE_M) &&
(env->v7m.fpccr[env->v7m.secure] & R_V7M_FPCCR_ASPEN_MASK) &&
(!(env->v7m.control[M_REG_S] & R_V7M_CONTROL_FPCA_MASK) ||
(env->v7m.secure &&
!(env->v7m.control[M_REG_S] & R_V7M_CONTROL_SFPA_MASK)))) {
/*
* ASPEN is set, but FPCA/SFPA indicate that there is no active
* FP context; we must create a new FP context before executing
* any FP insn.
*/
flags = FIELD_DP32(flags, TBFLAG_A32, NEW_FP_CTXT_NEEDED, 1);
}
*pflags = flags;
*cs_base = 0;
}

27
qemu/target/arm/translate.c
View file

@ -3545,6 +3545,33 @@ static int disas_vfp_insn(DisasContext *s, uint32_t insn)
/* Don't need to do this for any further FP insns in this TB */
s->v8m_fpccr_s_wrong = false;
}
if (s->v7m_new_fp_ctxt_needed) {
/*
* Create new FP context by updating CONTROL.FPCA, CONTROL.SFPA
* and the FPSCR.
*/
TCGv_i32 control, fpscr;
uint32_t bits = R_V7M_CONTROL_FPCA_MASK;
fpscr = load_cpu_field(s->uc, v7m.fpdscr[s->v8m_secure]);
gen_helper_vfp_set_fpscr(tcg_ctx, tcg_ctx->cpu_env, fpscr);
tcg_temp_free_i32(tcg_ctx, fpscr);
/*
* We don't need to arrange to end the TB, because the only
* parts of FPSCR which we cache in the TB flags are the VECLEN
* and VECSTRIDE, and those don't exist for M-profile.
*/
if (s->v8m_secure) {
bits |= R_V7M_CONTROL_SFPA_MASK;
}
control = load_cpu_field(s->uc, v7m.control[M_REG_S]);
tcg_gen_ori_i32(tcg_ctx, control, control, bits);
store_cpu_field(s, control, v7m.control[M_REG_S]);
/* Don't need to do this for any further FP insns in this TB */
s->v7m_new_fp_ctxt_needed = false;
}
}
if (extract32(insn, 28, 4) == 0xf) {

1
qemu/target/arm/translate.h
View file

@ -40,6 +40,7 @@ typedef struct DisasContext {
bool v8m_secure; /* true if v8M and we're in Secure mode */
bool v8m_stackcheck; /* true if we need to perform v8M stack limit checks */
bool v8m_fpccr_s_wrong; /* true if v8M FPCCR.S != v8m_secure */
bool v7m_new_fp_ctxt_needed; /* ASPEN set but no active FP context */
/* Immediate value in AArch32 SVC insn; must be set if is_jmp == DISAS_SWI
* so that top level loop can generate correct syndrome information.
*/