Re: [PATCH 2/2] xen: cleanup unrealized flash devices

[Philippe Mathieu-Daudé]

On 6/30/20 5:44 PM, Paul Durrant wrote:
>> -----Original Message-----
>> From: Philippe Mathieu-Daudé <philmd@redhat.com>
>> Sent: 30 June 2020 16:26
>> To: Paul Durrant <paul@xen.org>; xen-devel@lists.xenproject.org; 
>> qemu-devel@nongnu.org
>> Cc: Eduardo Habkost <ehabkost@redhat.com>; Michael S. Tsirkin 
>> <mst@redhat.com>; Paul Durrant
>> <pdurrant@amazon.com>; Jason Andryuk <jandryuk@gmail.com>; Paolo Bonzini 
>> <pbonzini@redhat.com>;
>> Richard Henderson <rth@twiddle.net>
>> Subject: Re: [PATCH 2/2] xen: cleanup unrealized flash devices
>>
>> On 6/24/20 2:18 PM, Paul Durrant wrote:
>>> From: Paul Durrant <pdurrant@amazon.com>
>>>
>>> The generic pc_machine_initfn() calls pc_system_flash_create() which creates
>>> 'system.flash0' and 'system.flash1' devices. These devices are then realized
>>> by pc_system_flash_map() which is called from pc_system_firmware_init() 
>>> which
>>> itself is called via pc_memory_init(). The latter however is not called when
>>> xen_enable() is true and hence the following assertion fails:
>>>
>>> qemu-system-i386: hw/core/qdev.c:439: qdev_assert_realized_properly:
>>> Assertion `dev->realized' failed
>>>
>>> These flash devices are unneeded when using Xen so this patch avoids the
>>> assertion by simply removing them using pc_system_flash_cleanup_unused().
>>>
>>> Reported-by: Jason Andryuk <jandryuk@gmail.com>
>>> Fixes: ebc29e1beab0 ("pc: Support firmware configuration with -blockdev")
>>> Signed-off-by: Paul Durrant <pdurrant@amazon.com>
>>> Tested-by: Jason Andryuk <jandryuk@gmail.com>
>>> ---
>>> Cc: Paolo Bonzini <pbonzini@redhat.com>
>>> Cc: Richard Henderson <rth@twiddle.net>
>>> Cc: Eduardo Habkost <ehabkost@redhat.com>
>>> Cc: "Michael S. Tsirkin" <mst@redhat.com>
>>> Cc: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
>>> ---
>>>  hw/i386/pc_piix.c    | 9 ++++++---
>>>  hw/i386/pc_sysfw.c   | 2 +-
>>>  include/hw/i386/pc.h | 1 +
>>>  3 files changed, 8 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
>>> index 1497d0e4ae..977d40afb8 100644
>>> --- a/hw/i386/pc_piix.c
>>> +++ b/hw/i386/pc_piix.c
>>> @@ -186,9 +186,12 @@ static void pc_init1(MachineState *machine,
>>>      if (!xen_enabled()) {
>>>          pc_memory_init(pcms, system_memory,
>>>                         rom_memory, &ram_memory);
>>> -    } else if (machine->kernel_filename != NULL) {
>>> -        /* For xen HVM direct kernel boot, load linux here */
>>> -        xen_load_linux(pcms);
>>> +    } else {
>>> +        pc_system_flash_cleanup_unused(pcms);
>>
>> TIL pc_system_flash_cleanup_unused().
>>
>> What about restricting at the source?
>>
> 
> And leave the devices in place? They are not relevant for Xen, so why not 
> clean up?

No, I meant to not create them in the first place, instead of
create+destroy.

Anyway what you did works, so I don't have any problem.

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>

> 
>   Paul
>  
>> -- >8 --
>> --- a/hw/i386/pc.c
>> +++ b/hw/i386/pc.c
>> @@ -1004,24 +1004,26 @@ void pc_memory_init(PCMachineState *pcms,
>>                                      &machine->device_memory->mr);
>>      }
>>
>> -    /* Initialize PC system firmware */
>> -    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,
>> -                           &error_fatal);
>> -    if (pcmc->pci_enabled) {
>> -        memory_region_set_readonly(option_rom_mr, true);
>> -    }
>> -    memory_region_add_subregion_overlap(rom_memory,
>> -                                        PC_ROM_MIN_VGA,
>> -                                        option_rom_mr,
>> -                                        1);
>> -
>>      fw_cfg = fw_cfg_arch_create(machine,
>>                                  x86ms->boot_cpus, x86ms->apic_id_limit);
>>
>> -    rom_set_fw(fw_cfg);
>> +    /* Initialize PC system firmware */
>> +    if (!xen_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,
>> +                               &error_fatal);
>> +        if (pcmc->pci_enabled) {
>> +            memory_region_set_readonly(option_rom_mr, true);
>> +        }
>> +        memory_region_add_subregion_overlap(rom_memory,
>> +                                            PC_ROM_MIN_VGA,
>> +                                            option_rom_mr,
>> +                                            1);
>> +
>> +        rom_set_fw(fw_cfg);
>> +    }
>>
>>      if (pcmc->has_reserved_memory && machine->device_memory->base) {
>>          uint64_t *val = g_malloc(sizeof(*val));
>> ---
>>
>>> +        if (machine->kernel_filename != NULL) {
>>> +            /* For xen HVM direct kernel boot, load linux here */
>>> +            xen_load_linux(pcms);
>>> +        }
>>>      }
>>>
>>>      gsi_state = pc_gsi_create(&x86ms->gsi, pcmc->pci_enabled);
>>> diff --git a/hw/i386/pc_sysfw.c b/hw/i386/pc_sysfw.c
>>> index ec2a3b3e7e..0ff47a4b59 100644
>>> --- a/hw/i386/pc_sysfw.c
>>> +++ b/hw/i386/pc_sysfw.c
>>> @@ -108,7 +108,7 @@ void pc_system_flash_create(PCMachineState *pcms)
>>>      }
>>>  }
>>>
>>> -static void pc_system_flash_cleanup_unused(PCMachineState *pcms)
>>> +void pc_system_flash_cleanup_unused(PCMachineState *pcms)
>>>  {
>>>      char *prop_name;
>>>      int i;
>>> diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
>>> index e6135c34d6..497f2b7ab7 100644
>>> --- a/include/hw/i386/pc.h
>>> +++ b/include/hw/i386/pc.h
>>> @@ -187,6 +187,7 @@ int cmos_get_fd_drive_type(FloppyDriveType fd0);
>>>
>>>  /* pc_sysfw.c */
>>>  void pc_system_flash_create(PCMachineState *pcms);
>>> +void pc_system_flash_cleanup_unused(PCMachineState *pcms);
>>>  void pc_system_firmware_init(PCMachineState *pcms, MemoryRegion 
>>> *rom_memory);
>>>
>>>  /* acpi-build.c */
>>>
> 
>