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

[Paul Durrant <xadimgnik@gmail.com>]

> -----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.

  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 */
> >>>
> >
> >