kvm: Make 'mmap_size' be 'int' in kvm_init_vcpu(), do_kvm_destroy_vcpu()

In kvm_init_vcpu()and do_kvm_destroy_vcpu(), the return value from
  kvm_ioctl(..., KVM_GET_VCPU_MMAP_SIZE, ...)
is an 'int', but we put it into a 'long' logal variable mmap_size.
Coverity then complains that there might be a truncation when we copy
that value into the 'int ret' which we use for returning a value in
an error-exit codepath. This can't ever actually overflow because
the value was in an 'int' to start with, but it makes more sense
to use 'int' for mmap_size so we don't do the widen-then-narrow
sequence in the first place.

Resolves: Coverity CID 1547515
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20240815131206.3231819-2-peter.maydell@linaro.org

accel/kvm/kvm-all.c

@@ -414,7 +414,7 @@ int kvm_create_and_park_vcpu(CPUState *cpu)
 static int do_kvm_destroy_vcpu(CPUState *cpu)
 {
     KVMState *s = kvm_state;
-    long mmap_size;
+    int mmap_size;
     int ret = 0;
 
     trace_kvm_destroy_vcpu(cpu->cpu_index, kvm_arch_vcpu_id(cpu));
@@ -459,7 +459,7 @@ void kvm_destroy_vcpu(CPUState *cpu)
 int kvm_init_vcpu(CPUState *cpu, Error **errp)
 {
     KVMState *s = kvm_state;
-    long mmap_size;
+    int mmap_size;
     int ret;
 
     trace_kvm_init_vcpu(cpu->cpu_index, kvm_arch_vcpu_id(cpu));