Re: [PATCH v1 01/14] s390x/s390-virtio-ccw: don't crash on weird RAM sizes

[David Hildenbrand]

On 10.09.24 19:57, David Hildenbrand wrote:
> KVM is not happy when starting a VM with weird RAM sizes:
>
>    # qemu-system-s390x --enable-kvm --nographic -m 1234K
>    qemu-system-s390x: kvm_set_user_memory_region: KVM_SET_USER_MEMORY_REGION
>      failed, slot=0, start=0x0, size=0x244000: Invalid argument
>    kvm_set_phys_mem: error registering slot: Invalid argument
>    Aborted (core dumped)
>
> Let's handle that in a better way by rejecting such weird RAM sizes
> right from the start:
>
>    # qemu-system-s390x --enable-kvm --nographic -m 1234K
>    qemu-system-s390x: ram size must be multiples of 1 MiB
>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>   hw/s390x/s390-virtio-ccw.c | 11 +++++++++++
>   1 file changed, 11 insertions(+)
>
> diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
> index 18240a0fd8..e30cf0a2a1 100644
> --- a/hw/s390x/s390-virtio-ccw.c
> +++ b/hw/s390x/s390-virtio-ccw.c
> @@ -180,6 +180,17 @@ static void s390_memory_init(MemoryRegion *ram)
>   {
>       MemoryRegion *sysmem = get_system_memory();
>   
> +    if (!QEMU_IS_ALIGNED(memory_region_size(ram), 1 * MiB)) {
> +        /*
> +         * The SCLP cannot possibly expose smaller granularity right now and 
> KVM
> +         * cannot handle smaller granularity. As we don't support NUMA, the
> +         * region size directly corresponds to machine->ram_size, and the 
> region
> +         * is a single RAM memory region.
> +         */
> +        error_report("ram size must be multiples of 1 MiB");
> +        exit(EXIT_FAILURE);
> +    }

I'll switch to

        error_setg(&error_fatal, "ram size must be multiples of 1 MiB");

here, to avoid the manual exit().

Please someone shout if I should keep it as is.

--
Cheers,

David / dhildenb