Jason Andryuk <jandr...@gmail.com> writes:
> On Wed, Jul 1, 2020 at 3:03 AM Paul Durrant <xadimg...@gmail.com> wrote:
>>
>> > -----Original Message-----
>> > From: Philippe Mathieu-Daudé <phi...@redhat.com>
>> > Sent: 30 June 2020 18:27
>> > To: p...@xen.org; xen-de...@lists.xenproject.org; qemu-devel@nongnu.org
>> > Cc: 'Eduardo Habkost' <ehabk...@redhat.com>; 'Michael S. Tsirkin'
>> > <m...@redhat.com>; 'Paul Durrant'
>> > <pdurr...@amazon.com>; 'Jason Andryuk' <jandr...@gmail.com>; 'Paolo
>> > Bonzini' <pbonz...@redhat.com>;
>> > 'Richard Henderson' <r...@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 <phi...@redhat.com>
>> > >> Sent: 30 June 2020 16:26
>> > >> To: Paul Durrant <p...@xen.org>; xen-de...@lists.xenproject.org;
>> > >> qemu-devel@nongnu.org
>> > >> Cc: Eduardo Habkost <ehabk...@redhat.com>; Michael S. Tsirkin
>> > >> <m...@redhat.com>; Paul Durrant
>> > >> <pdurr...@amazon.com>; Jason Andryuk <jandr...@gmail.com>; Paolo
>> > >> Bonzini <pbonz...@redhat.com>;
>> > >> Richard Henderson <r...@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 <pdurr...@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 <jandr...@gmail.com>
>> > >>> Fixes: ebc29e1beab0 ("pc: Support firmware configuration with
>> > >>> -blockdev")
>> > >>> Signed-off-by: Paul Durrant <pdurr...@amazon.com>
>> > >>> Tested-by: Jason Andryuk <jandr...@gmail.com>
>> > >>> ---
>> > >>> Cc: Paolo Bonzini <pbonz...@redhat.com>
>> > >>> Cc: Richard Henderson <r...@twiddle.net>
>> > >>> Cc: Eduardo Habkost <ehabk...@redhat.com>
>> > >>> Cc: "Michael S. Tsirkin" <m...@redhat.com>
>> > >>> Cc: Marcel Apfelbaum <marcel.apfelb...@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?
> """
>
> 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()?
commit ebc29e1beab02646702c8cb9a1d29b68f72ad503
pc: Support firmware configuration with -blockdev
[...]
Properties need to be created in .instance_init() methods. For PC
machines, that's pc_machine_initfn(). To make alias properties work,
we need to create the onboard flash devices there, too. [...]
For context, read the entire commit message. If you have questions
then, don't hesitate to ask them here.
