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target/arm: Implement dummy versions of M-profile FP-related registers

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The M-profile floating point support has three associated config
registers: FPCAR, FPCCR and FPDSCR. It also makes the registers
CPACR and NSACR have behaviour other than reads-as-zero.
Add support for all of these as simple reads-as-written registers.
We will hook up actual functionality later.

The main complexity here is handling the FPCCR register, which
has a mix of banked and unbanked bits.

Note that we don't share storage with the A-profile
cpu->cp15.nsacr and cpu->cp15.cpacr_el1, though the behaviour
is quite similar, for two reasons:
* the M profile CPACR is banked between security states
* it preserves the invariant that M profile uses no state
inside the cp15 substruct

Backports commit d33abe82c7c9847284a23e575e1078cccab540b5 from qemu
This commit is contained in:
Peter Maydell 2019-04-30 10:13:39 -04:00 committed by Lioncash
parent 978cd9c524
commit a4f332f3e9
No known key found for this signature in database
GPG key ID: 4E3C3CC1031BA9C7
2 changed files with 39 additions and 0 deletions
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5
qemu/target/arm/cpu.c
View file

@ -275,6 +275,11 @@ static void arm_cpu_reset(CPUState *s)
env->v7m.ccr[M_REG_S] |= R_V7M_CCR_UNALIGN_TRP_MASK;
}
if (arm_feature(env, ARM_FEATURE_VFP)) {
env->v7m.fpccr[M_REG_NS] = R_V7M_FPCCR_ASPEN_MASK;
env->v7m.fpccr[M_REG_S] = R_V7M_FPCCR_ASPEN_MASK |
R_V7M_FPCCR_LSPEN_MASK | R_V7M_FPCCR_S_MASK;
}
/* Unlike A/R profile, M profile defines the reset LR value */
env->regs[14] = 0xffffffff;

34
qemu/target/arm/cpu.h
View file

@ -522,6 +522,11 @@ typedef struct CPUARMState {
uint32_t scr[M_REG_NUM_BANKS];
uint32_t msplim[M_REG_NUM_BANKS];
uint32_t psplim[M_REG_NUM_BANKS];
uint32_t fpcar[M_REG_NUM_BANKS];
uint32_t fpccr[M_REG_NUM_BANKS];
uint32_t fpdscr[M_REG_NUM_BANKS];
uint32_t cpacr[M_REG_NUM_BANKS];
uint32_t nsacr;
} v7m;
/* Information associated with an exception about to be taken:
@ -1518,6 +1523,35 @@ FIELD(V7M_CSSELR, LEVEL, 1, 3)
*/
FIELD(V7M_CSSELR, INDEX, 0, 4)
/* v7M FPCCR bits */
FIELD(V7M_FPCCR, LSPACT, 0, 1)
FIELD(V7M_FPCCR, USER, 1, 1)
FIELD(V7M_FPCCR, S, 2, 1)
FIELD(V7M_FPCCR, THREAD, 3, 1)
FIELD(V7M_FPCCR, HFRDY, 4, 1)
FIELD(V7M_FPCCR, MMRDY, 5, 1)
FIELD(V7M_FPCCR, BFRDY, 6, 1)
FIELD(V7M_FPCCR, SFRDY, 7, 1)
FIELD(V7M_FPCCR, MONRDY, 8, 1)
FIELD(V7M_FPCCR, SPLIMVIOL, 9, 1)
FIELD(V7M_FPCCR, UFRDY, 10, 1)
FIELD(V7M_FPCCR, RES0, 11, 15)
FIELD(V7M_FPCCR, TS, 26, 1)
FIELD(V7M_FPCCR, CLRONRETS, 27, 1)
FIELD(V7M_FPCCR, CLRONRET, 28, 1)
FIELD(V7M_FPCCR, LSPENS, 29, 1)
FIELD(V7M_FPCCR, LSPEN, 30, 1)
FIELD(V7M_FPCCR, ASPEN, 31, 1)
/* These bits are banked. Others are non-banked and live in the M_REG_S bank */
#define R_V7M_FPCCR_BANKED_MASK \
(R_V7M_FPCCR_LSPACT_MASK | \
R_V7M_FPCCR_USER_MASK | \
R_V7M_FPCCR_THREAD_MASK | \
R_V7M_FPCCR_MMRDY_MASK | \
R_V7M_FPCCR_SPLIMVIOL_MASK | \
R_V7M_FPCCR_UFRDY_MASK | \
R_V7M_FPCCR_ASPEN_MASK)
/*
* System register ID fields.
*/