There is no direct relevance between CONFIG_KVM and NEED_CPU_H. Thus logic of
why using "#if defined CONFIG_KVM || !defined NEED_CPU_H" is hard to explain
and hard to understand.
The root cause is that we can not *always* get correct CONFIG_KVM, because:
- CONFIG_KVM is defined in [*-softmmu | *-linux-user]/config-target.h
- The "common" code outside folder [*-softmmu | *-linux-user] (in build time)
can NOT include config-target.h and can NOT *always* have valid CONFIG_KVM.
By removing "#if defined CONFIG_KVM || !defined NEED_CPU_H", we completely rely
on runtime value.
Advantage of applying this patch is: logic is clear
Disadvantage is: binary code for non-CONFIG_KVM target is bigger
(like sh4-softmmu or *-linux-user)
- kvm_enabled() is always runtime (kvm_allowed), and compiler won't optimize
if ( kvm_enabled() ) { ... } type of code.
- Before the patch, for condition (!CONFIG_KVM && NEED_CPU_H), above example
is preprocessed to be if (0) { ... } and then optimized
>From another perspective to explain why this patch does not cause troubles.
1) Before this patch, true value table:
--------------------------------------------------------------------------
kvm_enabled = runtime value? | CONFIG_KVM defined? | NEED_CPU_H defined? |
kvm_allowed | | |
kvm_irqchip_in_kernel | | |
... for the rest 7 defines | | |
--------------------------------------------------------------------------
runtime value | Y | Y |
runtime value | Y | N |
(a) const (0/false) | N | Y |
runtime value | N | N |
--------------------------------------------------------------------------
2) After this patch, true value table:
--------------------------------------------------------------------------
kvm_enabled = runtime value? | CONFIG_KVM defined? | NEED_CPU_H defined? |
... for the rest 8 defines | | |
--------------------------------------------------------------------------
runtime value | Y | Y |
runtime value | Y | N |
(b) runtime value (0/false) | N | Y |
runtime value | N | N |
--------------------------------------------------------------------------
- Logic of runtime value kvm_allowed is:
( (kvm_available() in arch_init.c) &&
((-machine accel=kvm) || (-enable-kvm) in runtime) )
- If CONFIG_KVM not defined, kvm_available() is always returns 0
- Thus for (b), runtime is always 0
- (b) is identical to (a)
- result of after patch is identical to before patch
Signed-off-by: Xuebing Wang <xbi...@gmail.com>
---
include/sysemu/kvm.h | 13 -------------
1 file changed, 13 deletions(-)
diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
index a02d67c..1829206 100644
--- a/include/sysemu/kvm.h
+++ b/include/sysemu/kvm.h
@@ -49,7 +49,6 @@ extern bool kvm_gsi_routing_allowed;
extern bool kvm_gsi_direct_mapping;
extern bool kvm_readonly_mem_allowed;
-#if defined CONFIG_KVM || !defined NEED_CPU_H
#define kvm_enabled() (kvm_allowed)
/**
* kvm_irqchip_in_kernel:
@@ -123,18 +122,6 @@ extern bool kvm_readonly_mem_allowed;
*/
#define kvm_readonly_mem_enabled() (kvm_readonly_mem_allowed)
-#else
-#define kvm_enabled() (0)
-#define kvm_irqchip_in_kernel() (false)
-#define kvm_async_interrupts_enabled() (false)
-#define kvm_halt_in_kernel() (false)
-#define kvm_irqfds_enabled() (false)
-#define kvm_msi_via_irqfd_enabled() (false)
-#define kvm_gsi_routing_allowed() (false)
-#define kvm_gsi_direct_mapping() (false)
-#define kvm_readonly_mem_enabled() (false)
-#endif
-
struct kvm_run;
struct kvm_lapic_state;
--
1.7.9.5
