From eeade0017698ada9d3049ec9021d094d96304f58 Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Mon, 4 Sep 2017 15:21:52 +0100 Subject: [PATCH] target/arm: Don't use cpsr_write/cpsr_read to transfer M profile XPSR 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 Reviewed-by: Richard Henderson Message-id: 1501692241-23310-11-git-send-email-peter.maydell@linaro.org --- target/arm/machine.c | 49 ++++++++++++++++++++++++++++++-------------- 1 file changed, 34 insertions(+), 15 deletions(-) diff --git a/target/arm/machine.c b/target/arm/machine.c index 2fb4b76296..3193b00b04 100644 --- a/target/arm/machine.c +++ b/target/arm/machine.c @@ -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);