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

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 7/1/20 2:25 PM, Jason Andryuk wrote:
> On Wed, Jul 1, 2020 at 3:03 AM Paul Durrant <xadimgnik@gmail.com> wrote:
>>
>>> -----Original Message-----
>>> From: Philippe Mathieu-Daudé <philmd@redhat.com>
>>> Sent: 30 June 2020 18:27
>>> To: 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 6/30/20 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.
>>
>> IIUC Jason originally tried restricting creation but encountered a problem because xen_enabled() would always return false at that point, because machine creation occurs before accelerators are initialized.
> 
> Correct.  Quoting my previous email:
> """
> Removing the call to pc_system_flash_create() from pc_machine_initfn()
> lets QEMU startup and run a Xen HVM again.  xen_enabled() doesn't work
> there since accelerators have not been initialized yes, I guess?

Ah, I missed that. You pointed at the bug here :)

I think pc_system_flash_create() shouldn't be called in init() but
realize().

> """
> 
> If you want to remove the creation in the first place, then I have two
> questions.  Why does pc_system_flash_create()/pc_pflash_create() get
> called so early creating the pflash devices?  Why aren't they just
> created as needed in pc_system_flash_map()?
> 
> Regards,
> Jason
> 
>>   Paul
>>
>>>
>>> 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 */
>>>>>>
>>>>
>>>>
>>
>>
>