On 11/08/2020 18:36, Greg Kurz wrote: > On Tue, 11 Aug 2020 18:05:21 +0200 > Laurent Vivier <lviv...@redhat.com> wrote: > >> On 11/08/2020 17:30, Greg Kurz wrote: >>> Since commit 61f20b9dc5b7 ("spapr_nvram: Pre-initialize the NVRAM to >>> support the -prom-env parameter"), pseries machines can pre-initialize >>> the "system" partition in the NVRAM with the data passed to all -prom-env >>> parameters on the QEMU command line. >>> >>> In this cases it is assumed that all the data fits in 64 KiB, but the user >>> can easily pass more and crash QEMU: >>> >>> $ qemu-system-ppc64 -M pseries $(for ((x=0;x<128;x++)); do \ >>> echo -n " -prom-env "$(for ((y=0;y<1024;y++)); do echo -n x ; done) ; \ >>> done) # this requires ~128 Kib >>> malloc(): corrupted top size >>> Aborted (core dumped) >>> >>> Call chrp_nvram_create_system_partition() first with its recently added >>> parameter dry_run set to false, to know the required size and allocate >>> the NVRAM buffer accordingly. >>> >>> Fixes: 61f20b9dc5b7 ("spapr_nvram: Pre-initialize the NVRAM to support the >>> -prom-env parameter") >>> Signed-off-by: Greg Kurz <gr...@kaod.org> >>> --- >>> hw/nvram/spapr_nvram.c | 4 ++++ >>> 1 file changed, 4 insertions(+) >>> >>> diff --git a/hw/nvram/spapr_nvram.c b/hw/nvram/spapr_nvram.c >>> index 992b818d34e7..1b74bec6200a 100644 >>> --- a/hw/nvram/spapr_nvram.c >>> +++ b/hw/nvram/spapr_nvram.c >>> @@ -165,6 +165,10 @@ static void spapr_nvram_realize(SpaprVioDevice *dev, >>> Error **errp) >>> if (ret < 0) { >>> return; >>> } >>> + } else if (nb_prom_envs > 0) { >>> + nvram->size = chrp_nvram_create_system_partition(NULL, >>> + MIN_NVRAM_SIZE / >>> 4, >>> + true); >> >> I think this will break the migration: the prom-env parameters can be on >> the source side without being on the dest side. And so the pram size > > Huh ? Migration mandates to have the same arguments on the command line, > and libvirt buys us that AFAIK or am I missing something ?
It's not true for all the arguments: take for instance the blockdev, the chardev, the netdev, vnc, ... I think it's true only for parameters that define the devices, the machine. And until now for prom-env it was not the case, look at the migration-test test case. Thanks, Laurent