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target/arm: Don't use cpsr_write/cpsr_read to transfer M profile XPSR

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For M profile the XPSR is a similar but not identical format to the
A profile CPSR/SPSR. (For instance the Thumb bit is in a different
place.) For guest accesses we make the M profile code go through
xpsr_read() and xpsr_write() which handle the different layout.
However for migration we use cpsr_read() and cpsr_write() to
marshal state into and out of the migration data stream. This
is pretty confusing and works more by luck than anything else.
Make M profile migration use xpsr_read() and xpsr_write() instead.

The most complicated part of this is handling the possibility
that the migration source is an older QEMU which hands us a
CPSR format value; helpfully we can always tell the two apart.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 1501692241-23310-11-git-send-email-peter.maydell@linaro.org
This commit is contained in:
Peter Maydell 2017-09-04 15:21:52 +01:00
parent e6ae5981ea
commit eeade00176
1 changed files with 34 additions and 15 deletions
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49
target/arm/machine.c
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@ -217,21 +217,37 @@ static int get_cpsr(QEMUFile *f, void *opaque, size_t size,
uint32_t val = qemu_get_be32(f);
if (arm_feature(env, ARM_FEATURE_M)) {
/* If the I or F bits are set then this is a migration from
* an old QEMU which still stored the M profile FAULTMASK
* and PRIMASK in env->daif. Set v7m.faultmask and v7m.primask
* accordingly, and then clear the bits so they don't confuse
* cpsr_write(). For a new QEMU, the bits here will always be
* clear, and the data is transferred using the
* vmstate_m_faultmask_primask subsection.
*/
if (val & CPSR_F) {
env->v7m.faultmask = 1;
if (val & XPSR_EXCP) {
/* This is a CPSR format value from an older QEMU. (We can tell
* because values transferred in XPSR format always have zero
* for the EXCP field, and CPSR format will always have bit 4
* set in CPSR_M.) Rearrange it into XPSR format. The significant
* differences are that the T bit is not in the same place, the
* primask/faultmask info may be in the CPSR I and F bits, and
* we do not want the mode bits.
*/
uint32_t newval = val;
newval &= (CPSR_NZCV | CPSR_Q | CPSR_IT | CPSR_GE);
if (val & CPSR_T) {
newval |= XPSR_T;
}
/* If the I or F bits are set then this is a migration from
* an old QEMU which still stored the M profile FAULTMASK
* and PRIMASK in env->daif. For a new QEMU, the data is
* transferred using the vmstate_m_faultmask_primask subsection.
*/
if (val & CPSR_F) {
env->v7m.faultmask = 1;
}
if (val & CPSR_I) {
env->v7m.primask = 1;
}
val = newval;
}
if (val & CPSR_I) {
env->v7m.primask = 1;
}
val &= ~(CPSR_F | CPSR_I);
/* Ignore the low bits, they are handled by vmstate_m. */
xpsr_write(env, val, ~XPSR_EXCP);
return 0;
}
env->aarch64 = ((val & PSTATE_nRW) == 0);
@ -252,7 +268,10 @@ static int put_cpsr(QEMUFile *f, void *opaque, size_t size,
CPUARMState *env = &cpu->env;
uint32_t val;
if (is_a64(env)) {
if (arm_feature(env, ARM_FEATURE_M)) {
/* The low 9 bits are v7m.exception, which is handled by vmstate_m. */
val = xpsr_read(env) & ~XPSR_EXCP;
} else if (is_a64(env)) {
val = pstate_read(env);
} else {
val = cpsr_read(env);