linux-kernel - Re: Hang on reboot in multi-core FreeBSD guest on Linux KVM host with Intel Sierra Forest CPU

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAMGffEmt2ZEL3uxRd+mWkKB=K8Q3seo9Kp-T06rZahxsX4Wm4Q@mail.gmail.com>
Date: Thu, 9 Oct 2025 13:21:50 +0200
From: Jinpu Wang <jinpu.wang@...os.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: fanwenyi0529@...il.com, kvm@...r.kernel.org, 
	Paolo Bonzini <pbonzini@...hat.com>, Xiaoyao Li <xiaoyao.li@...el.com>, linux-kernel@...r.kernel.org, 
	vkuznets@...hat.com
Subject: Re: Hang on reboot in multi-core FreeBSD guest on Linux KVM host with
 Intel Sierra Forest CPU

On Thu, Oct 9, 2025 at 5:44 AM Jinpu Wang <jinpu.wang@...os.com> wrote:
>
> Hi Sean,
>
> On Wed, Oct 8, 2025 at 5:55 PM Sean Christopherson <seanjc@...gle.com> wrote:
> >
> > Trimmed Cc: to drop people from the original thread.  In the future, just start
> > a new bug report.  Piggybacking a 10 year old bug just because the symptoms are
> > similar does more harm than good.  Whatever the old thread was chasing was already
> > fixed, _10 years_ ago; they were just trying to identy exactly what commit fixed
> > the problem.  I.e. whatever they were chasing _can't_ be the same root cause,
> > because even if it's literally the same code bug, it would require a code change
> > and thus a regression between v4.0 and v6.1.
> Thx for the reply,  it makes sense. I will remember this next time.
> >
> > On Wed, Oct 08, 2025, Jinpu Wang wrote:
> > > On Wed, Oct 8, 2025 at 2:44 PM Jack Wang <jinpu.wang@...os.com> wrote:
> > > > Sorry for bump this old thread, we hit same issue on Intel Sierra Forest
> > > > machines with LTS kernel 6.1/6.12, maybe KVM comunity could help fix it.
> >
> > Are there any host kernels that _do_ work?  E.g. have you tried a bleeding edge
> > host kernel?
> I will try linus/master today.
> >
> > > > ### **[BUG] Hang on FreeBSD Guest Reboot under KVM on Intel SierraForest (Xeon 6710E)**
> > > >
> > > > **Summary:**
> > > > Multi-cores FreeBSD guests hang during reboot under KVM on systems with
> > > > Intel(R) Xeon(R) 6710E (SierraForest). The issue is fully reproducible with
> > > > APICv enabled and disappears when disabling APICv (`enable_apicv=N`). The
> > > > same configuration works correctly on Ice Lake (Xeon Gold 6338).
> >
> > Does Sierra Forest have IPI virtualization?  If so, you could try running with
> > APICv enabled, but enable_ipiv=false to specifically disable IPI virtualization.
> Yes, it does:
> $  grep . /sys/module/kvm_intel/parameters/*
> /sys/module/kvm_intel/parameters/allow_smaller_maxphyaddr:N
> /sys/module/kvm_intel/parameters/dump_invalid_vmcs:N
> /sys/module/kvm_intel/parameters/emulate_invalid_guest_state:Y
> /sys/module/kvm_intel/parameters/enable_apicv:Y
> /sys/module/kvm_intel/parameters/enable_ipiv:Y
> /sys/module/kvm_intel/parameters/enable_shadow_vmcs:Y
> /sys/module/kvm_intel/parameters/ept:Y
> /sys/module/kvm_intel/parameters/eptad:Y
> /sys/module/kvm_intel/parameters/error_on_inconsistent_vmcs_config:Y
> /sys/module/kvm_intel/parameters/fasteoi:Y
> /sys/module/kvm_intel/parameters/flexpriority:Y
> /sys/module/kvm_intel/parameters/nested:Y
> /sys/module/kvm_intel/parameters/nested_early_check:N
> /sys/module/kvm_intel/parameters/ple_gap:128
> /sys/module/kvm_intel/parameters/ple_window:4096
> /sys/module/kvm_intel/parameters/ple_window_grow:2
> /sys/module/kvm_intel/parameters/ple_window_max:4294967295
> /sys/module/kvm_intel/parameters/ple_window_shrink:0
> /sys/module/kvm_intel/parameters/pml:Y
> /sys/module/kvm_intel/parameters/preemption_timer:Y
> /sys/module/kvm_intel/parameters/sgx:N
> /sys/module/kvm_intel/parameters/unrestricted_guest:Y
> /sys/module/kvm_intel/parameters/vmentry_l1d_flush:not required
> /sys/module/kvm_intel/parameters/vnmi:Y
> /sys/module/kvm_intel/parameters/vpid:Y
>
> I tried to disable ipiv, but it doesn't help. freebsd hang on reboot.
> sudo modprobe -r kvm_intel
> sudo modprobe  kvm_intel enable_ipiv=N
> /sys/module/kvm_intel/parameters/enable_ipiv:N
>
> Thx!
+cc Vitaly
Sorry, I missed one detail, we are use hyper-V enlightment features:
"+hv-relaxed,+hv-vapic,+hv-time,+hv-runtime,hv-spinlocks=0x1fff,+hv-vpindex,+hv-synic,+hv-stimer,+hv-tlbflush,hv-ipi."

did a lot tests with different features, and looks the hang is related
to  +hv-synic,+hv-stimer.  hv-synic seems the key which causes boot
hang of Freebsd 14.

But the problem seems fixed with FreeBSD 15?  I guess it's this fix:
https://github.com/systemd/systemd/issues/28001

Seems it's a bug from freebsd side, rather than on kvm side to me, but
I'm puzzled by disable apicv helps?

Thx!