kvm: x86: Establish IRQ0 override control

KVM is forced to disable the IRQ0 override when we run with in-kernel
irqchip but without IRQ routing support of the kernel. Set the fwcfg
value correspondingly. This aligns us with qemu-kvm.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

hw/pc.c

@@ -39,6 +39,7 @@
 #include "msi.h"
 #include "sysbus.h"
 #include "sysemu.h"
+#include "kvm.h"
 #include "blockdev.h"
 #include "ui/qemu-spice.h"
 #include "memory.h"
@@ -609,7 +610,7 @@ static void *bochs_bios_init(void)
     fw_cfg_add_i64(fw_cfg, FW_CFG_RAM_SIZE, (uint64_t)ram_size);
     fw_cfg_add_bytes(fw_cfg, FW_CFG_ACPI_TABLES, (uint8_t *)acpi_tables,
                      acpi_tables_len);
-    fw_cfg_add_bytes(fw_cfg, FW_CFG_IRQ0_OVERRIDE, &irq0override, 1);
+    fw_cfg_add_i32(fw_cfg, FW_CFG_IRQ0_OVERRIDE, kvm_allows_irq0_override());
 
     smbios_table = smbios_get_table(&smbios_len);
     if (smbios_table)

kvm-all.c

@@ -1307,6 +1307,11 @@ int kvm_has_gsi_routing(void)
     return kvm_check_extension(kvm_state, KVM_CAP_IRQ_ROUTING);
 }
 
+int kvm_allows_irq0_override(void)
+{
+    return !kvm_enabled() || !kvm_irqchip_in_kernel() || kvm_has_gsi_routing();
+}
+
 void kvm_setup_guest_memory(void *start, size_t size)
 {
     if (!kvm_has_sync_mmu()) {

kvm-stub.c

@@ -78,6 +78,11 @@ int kvm_has_many_ioeventfds(void)
     return 0;
 }
 
+int kvm_allows_irq0_override(void)
+{
+    return 1;
+}
+
 void kvm_setup_guest_memory(void *start, size_t size)
 {
 }

kvm.h

@@ -53,6 +53,8 @@ int kvm_has_xcrs(void);
 int kvm_has_many_ioeventfds(void);
 int kvm_has_gsi_routing(void);
 
+int kvm_allows_irq0_override(void);
+
 #ifdef NEED_CPU_H
 int kvm_init_vcpu(CPUState *env);
 

sysemu.h

@@ -102,7 +102,6 @@ extern int vga_interface_type;
 extern int graphic_width;
 extern int graphic_height;
 extern int graphic_depth;
-extern uint8_t irq0override;
 extern DisplayType display_type;
 extern const char *keyboard_layout;
 extern int win2k_install_hack;

vl.c

@@ -218,7 +218,6 @@ int no_reboot = 0;
 int no_shutdown = 0;
 int cursor_hide = 1;
 int graphic_rotate = 0;
-uint8_t irq0override = 1;
 const char *watchdog;
 QEMUOptionRom option_rom[MAX_OPTION_ROMS];
 int nb_option_roms;