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Re: [Qemu-devel] [PULL 22/25] target/i386: kvm: Add nested migration blo
From: |
Jan Kiszka |
Subject: |
Re: [Qemu-devel] [PULL 22/25] target/i386: kvm: Add nested migration blocker only when kernel lacks required capabilities |
Date: |
Mon, 8 Jul 2019 20:31:07 +0200 |
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Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666 |
On 21.06.19 13:30, Paolo Bonzini wrote:
> From: Liran Alon <address@hidden>
>
> Previous commits have added support for migration of nested virtualization
> workloads. This was done by utilising two new KVM capabilities:
> KVM_CAP_NESTED_STATE and KVM_CAP_EXCEPTION_PAYLOAD. Both which are
> required in order to correctly migrate such workloads.
>
> Therefore, change code to add a migration blocker for vCPUs exposed with
> Intel VMX or AMD SVM in case one of these kernel capabilities is
> missing.
>
> Signed-off-by: Liran Alon <address@hidden>
> Reviewed-by: Maran Wilson <address@hidden>
> Message-Id: <address@hidden>
> Signed-off-by: Paolo Bonzini <address@hidden>
> ---
> target/i386/kvm.c | 9 +++++++--
> target/i386/machine.c | 2 +-
> 2 files changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/target/i386/kvm.c b/target/i386/kvm.c
> index c931e9d..e4b4f57 100644
> --- a/target/i386/kvm.c
> +++ b/target/i386/kvm.c
> @@ -1640,9 +1640,14 @@ int kvm_arch_init_vcpu(CPUState *cs)
> !!(c->ecx & CPUID_EXT_SMX);
> }
>
> - if (cpu_has_nested_virt(env) && !nested_virt_mig_blocker) {
> + if (cpu_has_vmx(env) && !nested_virt_mig_blocker &&
> + ((kvm_max_nested_state_length() <= 0) || !has_exception_payload)) {
> error_setg(&nested_virt_mig_blocker,
> - "Nested virtualization does not support live migration
> yet");
> + "Kernel do not provide required capabilities for "
> + "nested virtualization migration. "
> + "(CAP_NESTED_STATE=%d, CAP_EXCEPTION_PAYLOAD=%d)",
> + kvm_max_nested_state_length() > 0,
> + has_exception_payload);
> r = migrate_add_blocker(nested_virt_mig_blocker, &local_err);
> if (local_err) {
> error_report_err(local_err);
> diff --git a/target/i386/machine.c b/target/i386/machine.c
> index fc49e5a..851b249 100644
> --- a/target/i386/machine.c
> +++ b/target/i386/machine.c
> @@ -233,7 +233,7 @@ static int cpu_pre_save(void *opaque)
>
> #ifdef CONFIG_KVM
> /* Verify we have nested virtualization state from kernel if required */
> - if (cpu_has_nested_virt(env) && !env->nested_state) {
> + if (kvm_enabled() && cpu_has_vmx(env) && !env->nested_state) {
> error_report("Guest enabled nested virtualization but kernel "
> "does not support saving of nested state");
> return -EINVAL;
>
Starting with this commit latest (bisection issue...), running Jailhouse in a
guest first stalls L1 (looks like we lose interrupts), and if I try to reset
that VM, I lose my host as well:
kvm: vmptrld (null)/6eb900000000 failed
kvm: vmclear fail: (null)/6eb900000000
and then things start to lock up because we seem to lose the CPUs the guest was
running on. Once I had this in the logs:
rcu: INFO: rcu_sched detected expedited stalls on CPUs/tasks: { 7-... } 15040
jiffies s: 4673 root: 0x80/.
rcu: blocking rcu_node structures:
Task dump for CPU 7:
qemu-system-x86 R running task 0 17413 17345 0x00000008
Call Trace:
? x86_virt_spec_ctrl+0x7/0xe0
? vmx_vcpu_run.part.0+0x2a4/0xfa0 [kvm_intel]
? vcpu_enter_guest+0x349/0xe80 [kvm]
? kvm_arch_vcpu_ioctl_run+0xff/0x550 [kvm]
? kvm_vcpu_ioctl+0x20d/0x590 [kvm]
? get_futex_key+0x35d/0x3b0
? do_vfs_ioctl+0x447/0x640
? do_futex+0x157/0x1d0
? ksys_ioctl+0x5e/0x90
? __x64_sys_ioctl+0x16/0x20
? do_syscall_64+0x60/0x120
? entry_SYSCALL_64_after_hwframe+0x49/0xbe
This was on a 5.1.16 distro kernel. Currently rebuilding 5.2 vanilla.
Looks like we have up to two critical bugs here...
Jan
--
Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux
- Re: [Qemu-devel] [PULL 22/25] target/i386: kvm: Add nested migration blocker only when kernel lacks required capabilities,
Jan Kiszka <=