Am 18.08.21 um 15:26 schrieb Claudio Imbrenda:
> Until now, destroying a protected guest was an entirely synchronous
> operation that could potentially take a very long time, depending on
> the size of the guest, due to the time needed to clean up the address
> space from protected pages.
>
> This patch implements a lazy destroy mechanism, that allows a protected
> guest to reboot significantly faster than previously.
>
> This is achieved by clearing the pages of the old guest in background.
> In case of reboot, the new guest will be able to run in the same
> address space almost immediately.
>
> The old protected guest is then only destroyed when all of its memory has
> been destroyed or otherwise made non protected.
>
> Signed-off-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
> ---
> arch/s390/kvm/kvm-s390.c | 6 +-
> arch/s390/kvm/kvm-s390.h | 2 +-
> arch/s390/kvm/pv.c | 132 ++++++++++++++++++++++++++++++++++++++-
> 3 files changed, 134 insertions(+), 6 deletions(-)
>
[...]
>
> +static int kvm_s390_pv_destroy_vm_thread(void *priv)
> +{
> + struct deferred_priv *p = priv;
> + u16 rc, rrc;
> + int r;
> +
> + /* Clear all the pages as long as we are not the only users of the mm */
> + s390_uv_destroy_range(p->mm, 1, 0, TASK_SIZE_MAX);
> + /*
> + * If we were the last user of the mm, synchronously free (and clear
> + * if needed) all pages.
> + * Otherwise simply decrease the reference counter; in this case we
> + * have already cleared all pages.
> + */
> + mmput(p->mm);
> +
> + r = uv_cmd_nodata(p->handle, UVC_CMD_DESTROY_SEC_CONF, &rc, &rrc);
> + WARN_ONCE(r, "protvirt destroy vm failed rc %x rrc %x", rc, rrc);
> + if (r) {
> + mmdrop(p->mm);
The comment about leaking makes more sense here, no?
Also
goto out_dont_free;
> + return r;
> + }
> + atomic_dec(&p->mm->context.is_protected);
> + mmdrop(p->mm);
> +
> + /*
> + * Intentional leak in case the destroy secure VM call fails. The
> + * call should never fail if the hardware is not broken.
> + */
> + free_pages(p->stor_base, get_order(uv_info.guest_base_stor_len));
> + free_pages(p->old_table, CRST_ALLOC_ORDER);
> + vfree(p->stor_var);
out_dont_free:
> + kfree(p);
> + return 0;
> +}
> +
[...]
