On 28.02.2018 20:53, Christian Borntraeger wrote:
> When a guests reboots with diagnose 308 subcode 3 it requests the memory
> to be cleared. We did not do it so far. This does not only violate the
> architecture, it also misses the chance to free up that memory on
> reboot, which would help on host memory over commitment. By using
> ram_block_discard_range we can cover both cases.
>
> Signed-off-by: Christian Borntraeger <borntrae...@de.ibm.com>
> ---
> target/s390x/kvm.c | 19 +++++++++++++++++++
> 1 file changed, 19 insertions(+)
>
> diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c
> index 8f3a422288..2e145ad5c3 100644
> --- a/target/s390x/kvm.c
> +++ b/target/s390x/kvm.c
> @@ -34,6 +34,8 @@
> #include "qapi/error.h"
> #include "qemu/error-report.h"
> #include "qemu/timer.h"
> +#include "qemu/rcu_queue.h"
> +#include "sysemu/cpus.h"
> #include "sysemu/sysemu.h"
> #include "sysemu/hw_accel.h"
> #include "hw/boards.h"
> @@ -41,6 +43,7 @@
> #include "sysemu/device_tree.h"
> #include "exec/gdbstub.h"
> #include "exec/address-spaces.h"
> +#include "exec/ram_addr.h"
> #include "trace.h"
> #include "qapi-event.h"
> #include "hw/s390x/s390-pci-inst.h"
> @@ -1841,6 +1844,14 @@ static int kvm_arch_handle_debug_exit(S390CPU *cpu)
> return ret;
> }
>
> +static void release_all_rams(void)
> +{
> + struct RAMBlock *rb;
> +
> + QLIST_FOREACH_RCU(rb, &ram_list.blocks, next)
> + ram_block_discard_range(rb, 0, rb->used_length);
> +}
> +
> int kvm_arch_handle_exit(CPUState *cs, struct kvm_run *run)
> {
> S390CPU *cpu = S390_CPU(cs);
> @@ -1853,6 +1864,14 @@ int kvm_arch_handle_exit(CPUState *cs, struct kvm_run
> *run)
> ret = handle_intercept(cpu);
> break;
> case KVM_EXIT_S390_RESET:
> + if (run->s390_reset_flags & KVM_S390_RESET_CLEAR) {
> + /*
> + * We will stop other CPUs anyway, avoid spurious crashes and
> + * get all CPUs out. The reset will take care of the resume.
> + */
> + pause_all_vcpus();
> + release_all_rams();
> + }
Hm, I have a patch lying around that tries to match pause/resume calls,
and only starts all CPUs again, once the last resume is called. (I
assume that there is the chance for a race between 2 callers of
pause/resume - you think it cannot happen, but as pause_all_vcpus() will
temporarily give up the qemu mutex, bad things can happen).
Can't we communicate that information to our ipl device and do the
clearing during the reset?
> s390_reipl_request();
> break;
> case KVM_EXIT_S390_TSCH:
>
--
Thanks,
David / dhildenb
