Re: [PULL v2 4/6] spapr: Add /chosen to FDT only at reset time to preserve kernel and initramdisk

From: Laurent Vivier <lvivier@redhat.com>
To: qemu-devel@nongnu.org
Cc: "Alexey Kardashevskiy" <aik@ozlabs.ru>,
	qemu-ppc@nongnu.org,
	"Mark Cave-Ayland" <mark.cave-ayland@ilande.co.uk>,
	"Cédric Le Goater" <clg@kaod.org>,
	"David Gibson" <david@gibson.dropbear.id.au>
Subject: Re: [PULL v2 4/6] spapr: Add /chosen to FDT only at reset time to preserve kernel and initramdisk
Date: Tue, 3 Dec 2019 16:57:01 +0100	[thread overview]
Message-ID: <a65399f9-fb59-a54b-3185-1f48ee979d3d@redhat.com> (raw)
In-Reply-To: <20191118105319.7658-5-lvivier@redhat.com>

On 18/11/2019 11:53, Laurent Vivier wrote:
> From: Alexey Kardashevskiy <aik@ozlabs.ru>
> 
> Since "spapr: Render full FDT on ibm,client-architecture-support" we build
> the entire flatten device tree (FDT) twice - at the reset time and
> when "ibm,client-architecture-support" (CAS) is called. The full FDT from
> CAS is then applied on top of the SLOF internal device tree.
> 
> This is mostly ok, however there is a case when the QEMU is started with
> -initrd and for some reason the guest decided to move/unpack the init RAM
> disk image - the guest correctly notifies SLOF about the change but
> at CAS it is overridden with the QEMU initial location addresses and
> the guest may fail to boot if the original initrd memory was changed.
> 
> This fixes the problem by only adding the /chosen node at the reset time
> to prevent the original QEMU's linux,initrd-start/linux,initrd-end to
> override the updated addresses.
> 
> This only treats /chosen differently as we know there is a special case
> already and it is unlikely anything else will need to change /chosen at CAS
> we are better off not touching /chosen after we handed it over to SLOF.
> 
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> Message-Id: <20191024041308.5673-1-aik@ozlabs.ru>
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
> ---
>  hw/ppc/spapr.c | 25 +++++++++++++++----------
>  1 file changed, 15 insertions(+), 10 deletions(-)
> 

This patch breaks pseries boot when we use a pci-bridge (since v4.2.0-rc0):

...
    -device pci-bridge,id=pci_bridge1,bus=pci.0,addr=0x3,chassis_nr=1 \
    -device virtio-scsi-pci,bus=pci_bridge1 \
...

OF stdout device is: /vdevice/vty@71000000
Preparing to boot Linux version 5.4.0-rc3+ (lvivier@localhost) (gcc
version 4.8.5 20150623 (Red Hat 4.8.5-39) (GCC)) #2 SMP Wed Nov 13
09:08:20 EST 2019
Detected machine type: 0000000000000101
command line: BOOT_IMAGE=/vmlinuz-5.4.0-rc3+ root=/dev/mapper/rhel-root
ro crashkernel=auto rd.lvm.lv=rhel/root rd.lvm.lv=rhel/swap
Max number of cores passed to firmware: 2048 (NR_CPUS = 2048)
Calling ibm,client-architecture-support...

( 300 ) Data Storage Exception [ 1dc5f230 ]

    R0 .. R7           R8 .. R15         R16 .. R23         R24 .. R31
8000000000001000   000000001e477010   0000000000000000   000000001dc17500
000000001e67afe0   0000000020000004   0000000000000000   000000001dc1bf88
000000001dc21800   000000001dc5f248   000000001e477010   0000000000000003
000000001dc61000   000000001e78dc2d   000000001dc1c158   000000000000f001
0000000000000000   a000000000000001   0000000000008000   000000001e67b060
000000001dc5f230   0000000000000000   000000000000f003   ffffffffffffffff
000000001e745860   0000000000000000   0000000000000006   000000001dbf48f8
000000001dc5f248   0000000000000000   000000001e67b050   000000001dc1c350

    CR / XER           LR / CTR          SRR0 / SRR1        DAR / DSISR
        80000808   000000001dbf34d4   000000001dbf4194   0000000020000004
0000000020000000   000000001dbf48f8   8000000000001000           40000000

4a >

Thanks,
Laurent