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Re: [Qemu-block] [PATCH 3/4] hw/i386/pc_sysfw: Let pc_system_firmware_in


From: Laszlo Ersek
Subject: Re: [Qemu-block] [PATCH 3/4] hw/i386/pc_sysfw: Let pc_system_firmware_init() access PCMachineState
Date: Tue, 5 Mar 2019 18:30:11 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1

On 03/04/19 20:48, Philippe Mathieu-Daudé wrote:
> PCMachineState will be used in the next patch.
> Since We can access PCMachineClass from it, directly use it.
> We can also access pcmc->pci_enabled, remove the isapc_ram_fw
> argument.
> 
> Signed-off-by: Markus Armbruster <address@hidden>
> [PMD: Extracted from bigger patch]
> Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
> ---
>  hw/i386/pc.c         | 2 +-
>  hw/i386/pc_sysfw.c   | 8 +++++---
>  include/hw/i386/pc.h | 3 +--
>  3 files changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> index 3889eccdc3..3cd8ed1794 100644
> --- a/hw/i386/pc.c
> +++ b/hw/i386/pc.c
> @@ -1830,7 +1830,7 @@ void pc_memory_init(PCMachineState *pcms,
>      }
>  
>      /* Initialize PC system firmware */
> -    pc_system_firmware_init(rom_memory, !pcmc->pci_enabled);
> +    pc_system_firmware_init(pcms, rom_memory);
>  
>      option_rom_mr = g_malloc(sizeof(*option_rom_mr));
>      memory_region_init_ram(option_rom_mr, NULL, "pc.rom", PC_ROM_SIZE,
> diff --git a/hw/i386/pc_sysfw.c b/hw/i386/pc_sysfw.c
> index 46b87afe23..55a3c563df 100644
> --- a/hw/i386/pc_sysfw.c
> +++ b/hw/i386/pc_sysfw.c
> @@ -231,15 +231,17 @@ static void old_pc_system_rom_init(MemoryRegion 
> *rom_memory, bool isapc_ram_fw)
>                                  bios);
>  }
>  
> -void pc_system_firmware_init(MemoryRegion *rom_memory, bool isapc_ram_fw)
> +void pc_system_firmware_init(PCMachineState *pcms,
> +                             MemoryRegion *rom_memory)
>  {
> +    PCMachineClass *pcmc = PC_MACHINE_GET_CLASS(pcms);
>      DriveInfo *pflash_drv;
>  
>      pflash_drv = drive_get(IF_PFLASH, 0, 0);
>  
> -    if (isapc_ram_fw || pflash_drv == NULL) {
> +    if (!pcmc->pci_enabled || pflash_drv == NULL) {
>          /* When a pflash drive is not found, use rom-mode */
> -        old_pc_system_rom_init(rom_memory, isapc_ram_fw);
> +        old_pc_system_rom_init(rom_memory, true);
>          return;
>      }
>  

This code extraction (as a pure refactoring) is incorrect.

In Markus's patch at
<https://lists.gnu.org/archive/html/qemu-devel/2019-02/msg06804.html>,
the condition that guards the old_pc_system_rom_init() call loses one
half of the disjunction:

-    if (isapc_ram_fw || pflash_drv == NULL) {
+    if (!pcmc->pci_enabled) {

namely the "pflash_drv == NULL" sub-condition. Therefore the
old_pc_system_rom_init() call can hardwire the second argument as "true":

-        old_pc_system_rom_init(rom_memory, isapc_ram_fw);
+        old_pc_system_rom_init(rom_memory, true);

However, in this refactoring, the (pflash_drv == NULL) subcondition is
not deleted; only the original condition is expressed differently.
Therefore we can't replace the "isapc_ram_fw" argument of
old_pc_system_rom_init() with plain "true", we have to use
"!pcmc->pci_enabled" instead.

However, if we write down "!pcmc->pci_enabled" twice for this purpose,
then it becomes too complex to read (for me anyway). So in that case I'd
even suggest keeping the "isapc_ram_fw" local variable, just turn it
into a normal local variable rather than take it as a parameter.

In the next patch, "isapc_ram_fw" can be killed just the same.

Thanks
Laszlo

> diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
> index 3ff127ebd0..eb7360feac 100644
> --- a/include/hw/i386/pc.h
> +++ b/include/hw/i386/pc.h
> @@ -278,8 +278,7 @@ extern PCIDevice *piix4_dev;
>  int piix4_init(PCIBus *bus, ISABus **isa_bus, int devfn);
>  
>  /* pc_sysfw.c */
> -void pc_system_firmware_init(MemoryRegion *rom_memory,
> -                             bool isapc_ram_fw);
> +void pc_system_firmware_init(PCMachineState *pcms, MemoryRegion *rom_memory);
>  
>  /* acpi-build.c */
>  void pc_madt_cpu_entry(AcpiDeviceIf *adev, int uid,
> 




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