/**
* write_cpustate_to_list:
* @cpu: ARMCPU
+ * @kvm_sync: true if this is for syncing back to KVM
*
* For each register listed in the ARMCPU cpreg_indexes list, write
* its value from the ARMCPUState structure into the cpreg_values list.
* This is used to copy info from TCG's working data structures into
* KVM or for outbound migration.
*
+ * @kvm_sync is true if we are doing this in order to sync the
+ * register state back to KVM. In this case we will only update
+ * values in the list if the previous list->cpustate sync actually
+ * successfully wrote the CPU state. Otherwise we will keep the value
+ * that is in the list.
+ *
* Returns: true if all register values were read correctly,
* false if some register was unknown or could not be read.
* Note that we do not stop early on failure -- we will attempt
* reading all registers in the list.
*/
-bool write_cpustate_to_list(ARMCPU *cpu);
+bool write_cpustate_to_list(ARMCPU *cpu, bool kvm_sync);
#define ARM_CPUID_TI915T 0x54029152
#define ARM_CPUID_TI925T 0x54029252
return true;
}
-bool write_cpustate_to_list(ARMCPU *cpu)
+bool write_cpustate_to_list(ARMCPU *cpu, bool kvm_sync)
{
/* Write the coprocessor state from cpu->env to the (index,value) list. */
int i;
for (i = 0; i < cpu->cpreg_array_len; i++) {
uint32_t regidx = kvm_to_cpreg_id(cpu->cpreg_indexes[i]);
const ARMCPRegInfo *ri;
+ uint64_t newval;
ri = get_arm_cp_reginfo(cpu->cp_regs, regidx);
if (!ri) {
if (ri->type & ARM_CP_NO_RAW) {
continue;
}
- cpu->cpreg_values[i] = read_raw_cp_reg(&cpu->env, ri);
+
+ newval = read_raw_cp_reg(&cpu->env, ri);
+ if (kvm_sync) {
+ /*
+ * Only sync if the previous list->cpustate sync succeeded.
+ * Rather than tracking the success/failure state for every
+ * item in the list, we just recheck "does the raw write we must
+ * have made in write_list_to_cpustate() read back OK" here.
+ */
+ uint64_t oldval = cpu->cpreg_values[i];
+
+ if (oldval == newval) {
+ continue;
+ }
+
+ write_raw_cp_reg(&cpu->env, ri, oldval);
+ if (read_raw_cp_reg(&cpu->env, ri) != oldval) {
+ continue;
+ }
+
+ write_raw_cp_reg(&cpu->env, ri, newval);
+ }
+ cpu->cpreg_values[i] = newval;
}
return ok;
}
return ret;
}
- /* Note that we do not call write_cpustate_to_list()
- * here, so we are only writing the tuple list back to
- * KVM. This is safe because nothing can change the
- * CPUARMState cp15 fields (in particular gdb accesses cannot)
- * and so there are no changes to sync. In fact syncing would
- * be wrong at this point: for a constant register where TCG and
- * KVM disagree about its value, the preceding write_list_to_cpustate()
- * would not have had any effect on the CPUARMState value (since the
- * register is read-only), and a write_cpustate_to_list() here would
- * then try to write the TCG value back into KVM -- this would either
- * fail or incorrectly change the value the guest sees.
- *
- * If we ever want to allow the user to modify cp15 registers via
- * the gdb stub, we would need to be more clever here (for instance
- * tracking the set of registers kvm_arch_get_registers() successfully
- * managed to update the CPUARMState with, and only allowing those
- * to be written back up into the kernel).
- */
+ write_cpustate_to_list(cpu, true);
+
if (!write_list_to_kvmstate(cpu, level)) {
return EINVAL;
}
return ret;
}
+ write_cpustate_to_list(cpu, true);
+
if (!write_list_to_kvmstate(cpu, level)) {
return EINVAL;
}
abort();
}
} else {
- if (!write_cpustate_to_list(cpu)) {
+ if (!write_cpustate_to_list(cpu, false)) {
/* This should never fail. */
abort();
}