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target/arm: Implement v8.1M NOCP handling

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From v8.1M, disabled-coprocessor handling changes slightly:
* coprocessors 8, 9, 14 and 15 are also governed by the
cp10 enable bit, like cp11
* an extra range of instruction patterns is considered
to be inside the coprocessor space

We previously marked these up with TODO comments; implement the
correct behaviour.

Unfortunately there is no ID register field which indicates this
behaviour. We could in theory test an unrelated ID register which
indicates guaranteed-to-be-in-v8.1M behaviour like ID_ISAR0.CmpBranch
>= 3 (low-overhead-loops), but it seems better to simply define a new
ARM_FEATURE_V8_1M feature flag and use it for this and other
new-in-v8.1M behaviour that isn't identifiable from the ID registers.

Backports commit 5d2555a1fe7370feeb1efbbf276a653040910017
This commit is contained in:
Peter Maydell 2021-03-01 20:16:08 -05:00 committed by Lioncash
parent 51093daf5f
commit 2dae268fcb
3 changed files with 21 additions and 5 deletions
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1
qemu/target/arm/cpu.h
View File

@ -1854,6 +1854,7 @@ enum arm_features {
ARM_FEATURE_VBAR, /* has cp15 VBAR */
ARM_FEATURE_M_SECURITY, /* M profile Security Extension */
ARM_FEATURE_M_MAIN, /* M profile Main Extension */
ARM_FEATURE_V8_1M, /* M profile extras only in v8.1M and later */
};
static inline int arm_feature(CPUARMState *env, int feature)

10
qemu/target/arm/m-nocp.decode
View File

@ -29,14 +29,16 @@
# If the coprocessor is not present or disabled then we will generate
# the NOCP exception; otherwise we let the insn through to the main decode.
&nocp cp
{
# Special cases which do not take an early NOCP: VLLDM and VLSTM
VLLDM_VLSTM 1110 1100 001 l:1 rn:4 0000 1010 0000 0000
# TODO: VSCCLRM (new in v8.1M) is similar:
#VSCCLRM 1110 1100 1-01 1111 ---- 1011 ---- ---0
NOCP 111- 1110 ---- ---- ---- cp:4 ---- ----
NOCP 111- 110- ---- ---- ---- cp:4 ---- ----
# TODO: From v8.1M onwards we will also want this range to NOCP
#NOCP_8_1 111- 1111 ---- ---- ---- ---- ---- ---- cp=10
NOCP 111- 1110 ---- ---- ---- cp:4 ---- ---- &nocp
NOCP 111- 110- ---- ---- ---- cp:4 ---- ---- &nocp
# From v8.1M onwards this range will also NOCP:
NOCP_8_1 111- 1111 ---- ---- ---- ---- ---- ---- &nocp cp=10
}

15
qemu/target/arm/translate-vfp.inc.c
View File

@ -3534,7 +3534,11 @@ static bool trans_NOCP(DisasContext *s, arg_NOCP *a)
if (a->cp == 11) {
a->cp = 10;
}
/* TODO: in v8.1M cp 8, 9, 14, 15 also are governed by the cp10 enable */
if (arm_dc_feature(s, ARM_FEATURE_V8_1M) &&
(a->cp == 8 || a->cp == 9 || a->cp == 14 || a->cp == 15)) {
/* in v8.1M cp 8, 9, 14, 15 also are governed by the cp10 enable */
a->cp = 10;
}
if (a->cp != 10) {
gen_exception_insn(s, s->pc_curr, EXCP_NOCP,
@ -3551,6 +3555,15 @@ static bool trans_NOCP(DisasContext *s, arg_NOCP *a)
return false;
}
static bool trans_NOCP_8_1(DisasContext *s, arg_nocp *a)
{
/* This range needs a coprocessor check for v8.1M and later only */
if (!arm_dc_feature(s, ARM_FEATURE_V8_1M)) {
return false;
}
return trans_NOCP(s, a);
}
static bool trans_VINS(DisasContext *s, arg_VINS *a)
{
TCGContext *tcg_ctx = s->uc->tcg_ctx;