Re: [PATCH v6 10/10] s390x: pv: Add dump support

[Steffen Eiden]

On 10/17/22 10:38, Janosch Frank wrote:
> Sometimes dumping a guest from the outside is the only way to get the
> data that is needed. This can be the case if a dumping mechanism like
> KDUMP hasn't been configured or data needs to be fetched at a specific
> point. Dumping a protected guest from the outside without help from
> fw/hw doesn't yield sufficient data to be useful. Hence we now
> introduce PV dump support.
>
> The PV dump support works by integrating the firmware into the dump
> process. New Ultravisor calls are used to initiate the dump process,
> dump cpu data, dump memory state and lastly complete the dump process.
> The UV calls are exposed by KVM via the new KVM_PV_DUMP command and
> its subcommands. The guest's data is fully encrypted and can only be
> decrypted by the entity that owns the customer communication key for
> the dumped guest. Also dumping needs to be allowed via a flag in the
> SE header.
>
> On the QEMU side of things we store the PV dump data in the newly
> introduced architecture ELF sections (storage state and completion
> data) and the cpu notes (for cpu dump data).
>
> Users can use the zgetdump tool to convert the encrypted QEMU dump to an
> unencrypted one.
>
> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: Steffen Eiden <seiden@linux.ibm.com>
> ---
>   dump/dump.c              |  12 +-
>   include/sysemu/dump.h    |   5 +
>   target/s390x/arch_dump.c | 262 +++++++++++++++++++++++++++++++++++----
>   3 files changed, 246 insertions(+), 33 deletions(-)
[ snip ]