Re: [PATCH 2/2] hw/riscv/virt.c: fix non-KVM --enable-debug build

[Richard Henderson]

On 8/29/23 16:51, Daniel Henrique Barboza wrote:
> > The compiler certainly does eliminate 0 && foo(), even at -O0.
> >
> > There must be something else going on.
> > Pointer to your tree?
>
> It's this tree:
>
> https://github.com/alistair23/qemu/tree/riscv-to-apply.next


Ok, so while -O0 will eliminate 0 && foo(), it doesn't eliminate with bar() && foo(), 
where bar must be inlined (multiple times in this case) to find the 0.

Moreover in the case of

> /usr/bin/ld: libqemu-riscv64-softmmu.fa.p/hw_intc_riscv_aplic.c.o: in function 
> `riscv_kvm_aplic_request':
> /home/danielhb/work/qemu/build/../hw/intc/riscv_aplic.c:486: undefined reference to 
> `kvm_set_irq'

this one, where foo (aka riscv_kvm_aplic_request) would have to be eliminated as well. 
But the compiler won't eliminate entire unused functions with -O0.

This seems to do the trick.  Whether it is aesthetically better than what you had with 
your patches, I will leave to someone else.


r~


diff --git a/hw/intc/riscv_aplic.c b/hw/intc/riscv_aplic.c
index 592c3ce768..0e22dcaf8a 100644
--- a/hw/intc/riscv_aplic.c
+++ b/hw/intc/riscv_aplic.c
@@ -481,10 +481,14 @@ static uint32_t riscv_aplic_idc_claimi(RISCVAPLICState *aplic, 
uint32_t idc)
     return topi;
 }

+#ifdef CONFIG_KVM
 static void riscv_kvm_aplic_request(void *opaque, int irq, int level)
 {
     kvm_set_irq(kvm_state, irq, !!level);
 }
+#else
+#define riscv_kvm_aplic_request  ({ qemu_build_not_reached(); NULL; })
+#endif

 static void riscv_aplic_request(void *opaque, int irq, int level)
 {
diff --git a/hw/riscv/virt.c b/hw/riscv/virt.c
index 388e52a294..b787ae38c2 100644
--- a/hw/riscv/virt.c
+++ b/hw/riscv/virt.c
@@ -782,7 +782,7 @@ static void create_fdt_sockets(RISCVVirtState *s, const MemMapEntry 
*memmap,
     }

     /* KVM AIA only has one APLIC instance */
-    if (virt_use_kvm_aia(s)) {
+    if (kvm_enabled() && virt_use_kvm_aia(s)) {
         create_fdt_socket_aplic(s, memmap, 0,
                                 msi_m_phandle, msi_s_phandle, phandle,
                                 &intc_phandles[0], xplic_phandles,
@@ -1461,7 +1461,7 @@ static void virt_machine_init(MachineState *machine)
         }
     }

-    if (virt_use_kvm_aia(s)) {
+    if (kvm_enabled() && virt_use_kvm_aia(s)) {
         kvm_riscv_aia_create(machine, IMSIC_MMIO_GROUP_MIN_SHIFT,
                              VIRT_IRQCHIP_NUM_SOURCES, VIRT_IRQCHIP_NUM_MSIS,
                              memmap[VIRT_APLIC_S].base,